Cathodic protection of carbon steel using zinc and magnesium as sacrificial anodes in different conductivity solutions

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Sabti This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3839295/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This work investigated the cathodic protection of carbon steel in different conductivity solutions using sacrificial anodes of zinc and magnesium. The effect of salt concentration (0.5–3.5% NaCl), the distance between structure and anode, and the area ratio of anode to cathodic on the protection efficiency was investigated and discussed. The consumption rate of sacrificial zinc and magnesium was evaluated for a range of operating conditions. High cathodic protection efficiency was obtained by Zn with low consumption rate compared to Mg. The Mg showed short lifespan and high potential shift to more positive and high protection current decrease after short time of applying the protection. Therefore, zinc is a successful sacrificial anode while magnesium is not recommended for long term protection for the range of salt concentrations investigated. cathodic protection sacrificial anode zinc magnesium anode consumption Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction Corrosion is the most destructive reaction of metals used in industry including petroleum industry as the corrosion reaction is considered a spontaneous reaction when appropriate conditions are available. According to recent reports the global cost of corrosions is around US $ 2.5 trillion, which should be reduced by using different corrosion control methods [Loto et al, 2019 ; Hu et al, 2022]. Cathode protection (CP) method is widely used in the oil and gas industry in order to prevent (or reduce) rust and corrosion of metal pipelines, tanks, and equipment. Underground pipes and tanks have been used worldwide for the transfer and storage of water, oil, gas, and other chemicals. Corrosion-related damages of these structures can lead to spoil of products, soil pollution, and environmental degradation. Cathodic protection (CP) by sacrificial anodes has numerous applications in practice especially in petroleum industry such as protection of: internals of water storage tanks, internals of fuel storage tanks, tank bottom, tank base from soil side, underground pipelines, internals of heat exchanger shells, ships, and others. Sacrificial anode cathodic protection is summarized by applying a potential more negative than − 850 millivolts versus copper/copper sulfate electrode. This potential is able to ensure the corrosion of metal almost zero in pH around 7 [Bahadori, 2014 ; Ameh, et al, 2017 , Gao et al, 2022 ]. The problem in sacrificial anode method is the instability of anode and the probability of fast consumption be the corrosive environment. However, the sacrificial anode cathodic protection has several advantages such as it does not need external power source, can be installed easily, and low maintenance cost [Prasad et al, 2021 ]. The cathodic protection by the sacrificial anode includes the use of high negativity metal (the anode) which ensures potential of more negative than − 0.85 V (vs. Cu/CuSO4) of the structure. This technique is used in limited areas and close distances, as the sacrificial anode cannot produce protection currents over long distances, because the protection voltage decreases when the structure to be protected moves away from the sacrificial anode due to the resistance polarization [Bhuiyan et al, 2019 , Wang et al, 2020 ]. The distance at which the sacrificial anode is effective is dependent on the electrochemical properties of anode, the resistivity of the medium, the size of the anode, and chemicals present in the medium. Zinc and Magnesium are the most competitive used metals as sacrificial anodes due to their high electrochemical activity [ Hasan and Aziz, 2017; Khadom, 2002; Yang et al, 2023 ]. Despite many years of research, their performance in certain environments is still not well understood, needing further investigation. In addition, the consumption rate of these sacrificial anodes is dependent on the nature of the corrosive medium [Khodary et al, 2019 ] and it needs to be evaluated at the operating conditions. The objective of this work is to investigate the effect of solution conductivity on the optimum cathodic protection conditions regarding the anode to cathode distance and area ratio (AR) using zinc and magnesium anodes. In addition, it is aimed to compare the efficiency of Zn and Mg under different operating conditions. 2. Experimental work Figure 1 shows the experimental setup which comprises a water bath, digital voltmeter to measure the structure potential, ammeter to measure the current, saturated calomel electrode (SCE) as a reference electrode, and heater and controller to set the required temperature. Digital balance of high accuracy (4 decimal places of a gram) to measure the weight loss. Optical Microscope (type of KRUS/ Germany) was used for surface inspection after corrosion and after applying cathodic protection. Pure zinc (sheet) and pure magnesium (strip) were used as a sacrificial anode. Three different NaCl solutions were used (0.5%, 1%, 3.5% wt.%) at 30 o C. The carbon steel specimen used was a cylindrical rod with dimensions of 150 mm long and 10 mm in diameter. The zinc specimen sheet dimensions were 45×45×1.4 mm and of Mg strip were 200×140 mm. Three values of anode to cathode distance were investigated namely, 100, 200, 300 mm and different values of anode to cathode area ratios (AR). At first, the free corrosion rates were determined for different conditions. The specimen is prepared in several steps starting from the sanding process, which includes the use of emery papers in several degrees: 120, 400, 600, and 2000 to obtain a clean surface free of dirt. After that, the specimen was washed with distilled water several times and then dried with a clean tissue, after which it is placed in acetone for three minutes to remove the deposits if any. In the next step, the specimen was washed with distilled water, then dried with a clean tissue and heated in an oven at 80 o C for 5 minutes. The specimen was then stored in a vacuum desiccator over a high activity silica to preserve it from humidity until use. The specimen was then weighed to measure the initial weight. The salt solution is prepared from sodium chloride in different concentrations (0.5%, 1%, 3.5% wt). At each concentration, the specimen is immersed in the solution and left for four hours to experience corrosion, where the specimen is submerged at a depth of 80 mm below the surface. After the end of the specified time, the specimen is extracted, washed with distilled water, then cleaned with a smooth plastic brush, to remove corrosion product layer well, then was dried with a clean tissue, immersed back in acetone for three minutes, washed again with distilled water, dried and weighed to obtain the weight loss. When applying the cathodic protection (CP) the same procedure is followed to obtain the weight loss in the presence of CP. The corrosion rate is obtained using to the following equation [Kilbane, 2017 ; Ali and Hasan, 2020 ]: $$\text{C}\text{R} \left(\text{i}\text{n} \text{g}\text{m}\text{d}\right)=\frac{\text{w}\text{e}\text{i}\text{g}\text{h}\text{t}\text{l}\text{o}\text{s}\text{s}\left(\text{g}\right)}{\text{A}\text{r}\text{e}\text{a}\left({\text{m}}^{2}\right)\times \text{T}\text{i}\text{m}\text{e} \left(\text{d}\text{a}\text{y}\right)}$$ 1 …………… Where CR represents corrosion rate in g/m 2 .d (gmd). The protection percent (pp) was calculated as: $$\text{P}\text{P}\text{\%}=\left(\frac{\text{C}{\text{R}}_{0}-\text{C}\text{R}}{\text{C}{\text{R}}_{0}}\right)\text{X} \text{l}00$$ 2 ……..…….. CR 0 and CR are the corrosion rates in absence and in presence of sacrificial anodes respectively. In sacrificial anode experiments, the NaCl solution was prepared and heated in the plastic water to constant temperatures of 30 o C. Then, the specimen was immersed and the electrical circuit was switched on. The current and voltage was recorded with time until the end of test duration. The structure potential was measured versus standard calomel electrode (SCE). The capillary tube was placed at a distance of 2 mm from the specimen and connected to the calomel electrode to measure the specimen potential. The specimens’ analyses are shown in Table 1 to 3 as analyzed in Material Research Center/Ministry of Sciences and Technology. Table 4 lists the solutions electrical conductivity as measured experimentally using conductivity meter. Table 1 Carbon steel Chemical Composition Elements Fe P Sn Pb Mn S Ni Si B Mo Weight% 98.6 Less than 0.0005 Less than 0.001 Less than 0.001 0.510 Less than 0.001 0.0340 0.202 Less than 0.0005 0.0107 Al As Cu Bi Se Zr Co Ti V W 0.0283 Less than 0.0005 0.0464 Less than 0.0015 Less than 0.001 0.0026 Less than 0.001 0.0011 0.0012 0.0081 Zn Cr As Ca Nb Sb Ta 0.0036 0.165 Less than 0.0005 Less than 0.0005 Less than 0.001 Less than 0.005 0.0126 Table 2 Zinc Chemical Composition Elements Zn Pb Sn Pb Mn Fe Ni Si Weight% 99.9 0.0046 0.0024 0.0046 0.0009 Less than 0.002 0.0072 0.0009 Al Cd Cu Bi Ag Hg ln Tl 0.0051 0.0013 0.0063 0.0002 0.0001 0.0006 0.0001 0.0012 Mg Cr As Sb 0.0002 Less than 0.0005 0.0001 Less than 0.001 Table 3 Magnesium Chemical composition Elements Mg Pb Sn Pb Mn Fe Ni Si Ce Dy Weight% 99.8 0.170 Less than 0.001 0.0046 Less than 0.002 Less than 0.002 Less than 0.0002 Less than 0.0005 Less than 0.025 Less than 0.005 Al Cd Cu Bi Ag Hg ln Ho Er Gd 0.003 0.0009 0.002 0.0002 Less than 0.001 0.0006 0.0001 Less than 0.005 Less than 0.005 Less than 0.005 Mg Cr As Ca Be Fe Zn Sr La Lu 0.0002 Less than 0.0005 0.0001 Less than 0.0001 0.0001 0.0161 0.0011 0.0001 Less than 0.002 Less than 0.0005 Nd Pr Sm Tb Th Tm Y Yb Zr Li Less than 0.025 Less than 0.015 Less than 0.005 Less than 0.0002 Less than 0.025 Less than 0.005 Less than 0.005 Less than 0.001 Less than 0.0025 Less than 0.001 Table 4 NaCl Solution conductivity [Widodo et al, 2018] NaCl concentration, wt% Conductivity, mS/cm 0.5 18.5 1.0 32.1 3.5 95.2 3. Result and discussion. 3.1 Free corrosion The free corrosion rate, before applying cathodic protection, was determined by measuring the weight loss in different conductivity solutions as listed in Table 5 . At low concentration (0.5%), the corrosion rate is low, with the increase in the concentration of salt to 1%, the corrosion rate increases appreciably due the increased conductivity. At highest concentration it increases little further. The high concentration of NaCl causes a decrease in dissolved oxygen concentration and a formation of effective corrosion leading to restrain the corrosion attack [Revie and Uhlig, 2008 , Slaiman and Hasan, 2010 ]. Table 5 Corrosion rate of CS in different NaCl Solutions NaCl Concentration gmd 0.5% 8.8 1% 14.1 3.5% 15.1 3.2 Cathodic Protection by Zinc Anode Tables 6 through 8 list the values of corrosion rates of CS for different experimental conditions under the application of cathodic protection by zinc anode. Table 2 for cathodic protection in 0.5% NaCl solution shows that for 5% area ratio of Zn anode to structure (CS) the cathodic protection reaches 76% at the shortest distance between anode and structure (100 mm). When the distance is increased to 3 times (to 300 mm apart), the CP decreases to 58%; i.e. decrease by about 14%. For area ratio (AR) of 17%, the CP is 100% at distance 100 mm and 95% at 300 mm. The decrease in CP with distance is ascribed to the increased solution resistance to current flow which causes a potential drop leading to a departure from the protection potential. It is evident that the 17% area ratio gives higher CP than 5% for all distances. 100% protection is attained at a distance of 100 mm indicating no need to go for a higher area ratio. Increase in protection percent with anode to cathode area ratio has also been reported by Hamad [ 2015 ]. The larger the area of zinc, the better the protection because the large area provides more electrons that are more uniformly distributed on the steel surface [Loto and Popoola, 2011 ]. Table 7 for cathodic protection in 1% NaCl, the same trend of CP for the case of 0.5% with distance and with aera ratio is noticed. However, the cathodic protection is generally high than the case of 0.5%. The same behavior is true for case of 3.5% as shown in Table 8 . Accordingly, no systematic trend of CP efficiency with salt concentration or solution conductivity can be noticed in present work. The higher the salt concentration or higher medium conductivity is the better the flow of protection current that causes a reduction of O2 on the cathode surface leading to better protection. However, the more corrosive medium can cause faster damage to the anode due to higher consumption rate leading to reduce the efficiency of protection. Additionally, when the effectiveness of the anode decreases with time, the structure starts to corrode and a thin film of corrosion product layer forms which may reduce the corrosion rate [Su et al, 2023 , Yang et al, 2023 ] or enhance it by increasing the turbulence at the surface at flow conditions [Slaiman and Hasan, 2010 ]. All these factors make the behavior of CP percent with time more complicated. Figure 2 presents microscopic images of CS specimens before exposure to corrosive solution, after exposure to corrosive solution, and after applying cathodic protection by Zn anode. It is evident that after corrosion there is a clear corrosion damage on the surface image 2. When using cathodic protection, the surface is less corroded as shown in image 3. Table 6 Corrosion rate and cathodic protection percent using Zn for the parameter range investigated at NaCl concentration of 0.5%. Concentration of NaCl AR Distance, mm CR CP% 0.5% 5% 100 2.096 76% 200 3.205 64% 300 3.699 58% 17% 100 0.000 100% 200 0.247 97% 300 0.370 95% Table 7 CR rate and cathodic protection percent using Zn for the parameter range investigated at NaCl concentration of 1%. Concentration of NaCl AR Distance, mm CR CP% 1% 5% 100 1.481 91% 200 4.562 73% 300 5.548 67% 17% 100 0.0 100% 200 0.247 98% 300 0.123 98% Table 8 CR rate and cathodic protection percent using Zn for the parameter range investigated at NaCl concentration of 3.5%. Concentration of NaCl AR Distance, mm CR CP% 3.5% 5% 100 1.97 76% 200 2.10 75% 300 2.34 72% 17% 100 0.0 100% 200 0.0 100% 300 0.0 100% 3.3 Cathodic Protection by Magnesium Table 9 through 11 presents the values of cathodic protection percent using Mg anode for different salt concentrations, area ratios, and cathode to anode distance. For 0.5% NaCl solution, the cathodic protection percent for 17% Mg to structure area ratio is 50% at distance 100 mm decreasing to 40% at distance 300 mm. This means increasing the distance 3 times causes a decrease in CP by about 20%. The CP for 34% AR, the relevant values increases to 79% and 58%, i.e. increasing the distance 3 times causes a decrease in CP by 16.6%. Table 10 for NaCl concentration of 1%, reveals the same behavior of 0.5% NaCl with higher CP percent. For the case of 3.5% NaCl solution shown in Table 11 , the CP % is much lower than that of 0.5% and 1% indicating that the Mg anode provides poor protection in high salt media. This is ascribed to the occurrence of severe free corrosion of Mg in 3.5% NaCl solution because the lifespan of Mg in this corrosive solution is too short. Table 9 indictates also that increasing the area ratio of Mg from 17–34% causes an increase in cathodic protection percent by 45 to 60 percent depending on the distance between anode and cathode. The same behavior is true for Tables 10 and 11 . Close behavior has also been observed by Loto et al, [ 2019 ] for Mg anodes in 0.5M HCl. Table 9 CR rate and cathodic protection percent using Mg for the parameter range investigated at NaCl concentration of 0.5%. Concentration of NaCl AR Distance, mm CR CP% 0.5% 17% 100 4.43 50% 200 4.8 45% 300 5.30 40% 34% 100 1.85 79% 200 2.96 66% 300 3.70 58% Table 10 CR rate and cathodic protection percent using Mg for the parameter range investigated at NaCl concentration of 1%. Concentration of NaCl AR Distance, mm CR CP% 1% 17% 100 5.30 69% 200 5.80 66% 300 6.29 63% 34% 100 3.58 79% 200 5.55 67% 300 6.41 62% Table 11 CR rate and cathodic protection percent using Mg for the parameter range investigated at NaCl concentration of 3.5%. Concentration of NaCl AR Distance, mm CR, gmd CP% 3.5% 17% 100 2.22 73% 200 2.59 69% 300 3.58 57% 34% 100 2.22 73% 200 3.83 54% 300 5.06 49% 3.4 Consumption rate of the anodes Table 12 presents the consumption rate (expressed by corrosion rate unit g/m 2 .day) of of Mg and Zn when used as sacrificial anodes to protect carbon steel in different NaCl concentartions. It can be seen that the corrosion rate of Mg is higher than Zn although Zn gives higher protection perecent. This indicates that the use of Zn is more successful than Mg in the range of solutions conductivites investigated in this work. This agrees with the findings of Sadawy et al. [ 2020 ]. The high activity of Mg, increases its corrosion in salt solutions leading to a decrease in its activity and surface area with time. The consumption of Zn and Mg is due to the anodic dissolution that provide the requred currents to portect the CS as follows: Zn = Zn 2+ + 2e (1) Mg = Mg + + 2e (2) The liberated electrons will flow through the connection were to be used up on the cathode surface in oxygen reduction reaction leading avoide ther reaction of iron with O 2 , i.e, restrain the corrosion of carbon steel. The cathodic reaction on the steel surface is: O2 + 2H 2 O + 4e = 4OH − (3) The consumption rate of the used anodes is influenced by solution conductivity, the distance between anode and structure, and the deposits formed on anode surface which influence its activity. Table 12 indicates no systematic trend of the consumption rate of anodes with salt concentration or with cathodic protection percent which can be attributed to the complicated phenomena occurring on anode and cathode surfaces. Khodary et al, [ 2019 ] reported slight increase in Zn consumption rate with the NaCl solution for a long time when used to protect CS. Table 11 Corrosion rate of anodes used versus protection attained NaCl concentration CR (gmd) CPP Zinc Area ratio 5% Mg Area ratio 17% Zinc Mg 0.5% 2.09 4.44 76% 50% 1% 1.48 5.31 91% 69% 3.5% 1.97 2.30 76% 73% 3.5 Protection potentials Figure 3 presents the typical trend of protection potential versus time for Zn anode at different conditions. It can be noted that for small distance (100 mm), the protection potential is very stable indicating efficient anode performance. The same observation was reported by previous investiagtors [Loto and Popoola, 2011 ; So et al, 2023 ]. However, there is a slight shift to more positive direction for distance beyond that but the potential is still more negative than − 0.9 V (SCE) which provides good protection. This explains the high cathodic protection percent for zinc shown in Tables 6 to 8 . Figure 4 shows the typical trend of protection potential with time when using Mg as a sacrificial anode. It can be seen that the structure potential shifts sharply to more positive at the initial period of cathodic protection application. Within about 25 min, the potential changes by about 63% to more positive reaching potenatials of -0.6 to -0.5 V (SCE) indicating the corrosion zone. Similar behavior of zinc consmption rate has been reported by Ziadane et al [2018] when protecting CS tanks against hot corrosion. 3.6 Protection currents Figures 5 and 6 shows the trend of protection currents with time for Zn and Mg, respectively, for different anode to cathode distances. The protection current requirement is the amount of current needed to achieve full cathodic protection to the structural surface [Brondel, et al, 1994 ; Bhuiyan et al, 2019 ]. It can be noticed that the protection current decreases with time for all the distance. This can be attributed to a decrease in the efficiency of the sacrificed anode with time due to the potential shift toward more positive, which makes it unable of providing the required protection current for the full protection [Meredith, 1989; Hasan and Abdul-Jabbar; 2011 , Lotto and Popoola, 2011]. For Mg, it can be seen that the protection current is initially very high (much higher than Zn current) but it drops sharply at the first 60 minutes of the run reaching almost zero current. This means that for the remaining 3 hours of experiment, the Mg is no longer working. Due to high potential drop and high consumption rate of Mg due to the large polarization the current decreases appreciably leading to a poor protection after a short time. The high reduction in the protection current with time is ascribed to the fast dissolution of magnesium anodes in salty solution which reduces the area of the anodes as has been seen by visual observation in this work. The mechanism of cathodic protection of the current system can be explained briefly. When the current is imposed by connecting the structure (CS) to the scarifying active anode, the flow of electrons through the wire reduces the dissolved O 2 on the structure surface leading to form hydroxyl ion as in Eq. (3). Therefore, instead of O 2 reaction with iron, it reacts with electrons leading to avoid or reduce the corrosion [Hasan 2014 ]. At the anode (Zn on Mg) the anodic reaction occurs according to Eq. ( 1 ) or (2). When the activity of anodes decreases with time, its ability to shift the CS potential to more negative decreases leading to a shift in the potential to more positive as shown in Figs. 2 and 3 . When the CS becomes more positive than − 0.85 vs (SCE), the CS starts to undergo corrosion damage. The rate of corrosion depends on the departure of potential from the protection potential. The higher the potential departure, the higher the corrosion rate of the structure. That is why the corrosion rate of the structure (CS) when using Mg is generally higher than that when using Zn even when using a high area ratio of Mg. Number of authors [Freiman and Kuznetsova, 2001; Leeds, 2007; Kajiyama and Okamura, 1999; Angst et al, 2016 ] reported that the cathodic protection of steel is attained by increasing the pH at the structure surface due to formation of OH - . In several situations the formation of film close to the metal surface causes an increase in the pH which favors the passivation of steel and therefore, it provides protection from further corrosion attack [Angst et al, 2016 ]. 4. Conclusions The use of Zn and Mg for cathodic protection (CP) of carbon steel in different NaCl solutions (0.5–3.5% wt) revealed several conclusions. Zinc is generally successful in providing efficient protection for the range of NaCl concentration investigated. It can provide more than 95% protection when placed within 300 apart from the structure with an area ratio of 17%. In addition, its consumption rate is relatively low even at high salt concentration. The protection potential and currents of Zn are relatively stable for long time which provides a successful performance. The Mg anode is not effectively protecting the structure in this range of salt concentrations especially for long term protection. This is due to its fast depreciation leading to a shift in structure potential to more positive quickly. Even when using a large area ratio of Mg to steel, the protection efficiency is low. The protection current drops to almost zero after about 1 h of applying the CP. The protection potential shifts to more positive by 63% after about 25 min. Therefore, Mg is not recommended for high conductivity solutions. Increasing the area ratio of Zn to structure (CS) from 5–17% caused an increase in the protection efficiency b 30%. The larger the distance between anode to cathode, the lower the cathodic protection efficiency. Increasing the distance between anode and structure from 100 mm to 300 mm, causes a decrease in cathodic protection percent by up to 22% for Zn and 22% for Mg depending on area ratio and solution conductivity. Abbreviations AR area ratio CP cathodic protection CR corrosion rate CS carbon steel gmd gram/m 2 . day PP protection percent SCE standard calomel electrode Declarations Conflict of interest: On behalf of all the authors of this article, the corresponding author confirm that there is no conflict of interest. Author contributions Basim O. Hasan: proposed the idea, wrote the discussion and reviewed the whole manuscript, Amel A. Beden: carried out the experimental measurements, Hamza K. Sabti, installed the rig, wrote part of the discussion, and editing. References Ali ME, Hasan BO (2020) Galvanic corrosion of carbon steel under concentration cell formation in MgCl. 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Constr Build Mater 246:118476 Widodo CS, Sela H, Santosa DR (2021) The effect of NaCl concentration on the ionic NaCl solutions electrical impedance value using electrochemical impedance spectroscopy methods, AIP Conf. Proc. 2021, 050003(2018) Yang Y, Cao S, Ying T, Cao F, Wang J, Zhu Q, Zeng X (2023) The effects of a corrosion product film on the corrosion behavior of Mg-Al alloy with micro-alloying of yttrium in a chloride solution. Corros Commun 11:12–22 Zidane N, Ait Albrimi Y, Ait Addi A, Douch J, Souto RM, Hamdani M 1 (2018) Evaluation of the Corrosion of AZ31 Magnesium Alloy Used as Sacrificial Anode for Cathodic Protection of Hot-Water Tank Storage Containing Chloride. Int J Electrochem Sci 13:29–44 So Y, Park E-H, Kim J-G (2023) Effect of Zinc Addition in Filler Metal on Sacrificial Anode Cathodic Protection of Fin-Tube Aluminum Heat Exchanger. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3839295","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":266926146,"identity":"3ab8e48f-33bb-4b80-83a7-8802c5c3ea14","order_by":0,"name":"Amal Abd Al-Hussein Beden","email":"","orcid":"","institution":"Republic of Iraq Ministry of Oil","correspondingAuthor":false,"prefix":"","firstName":"Amal","middleName":"Abd Al-Hussein","lastName":"Beden","suffix":""},{"id":266926147,"identity":"5edeb5d1-cf8d-4221-bef3-db8c760ed62f","order_by":1,"name":"Basim Hasan","email":"data:image/png;base64,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","orcid":"https://orcid.org/0000-0001-6774-562X","institution":"Al-Nahrain University","correspondingAuthor":true,"prefix":"","firstName":"Basim","middleName":"","lastName":"Hasan","suffix":""},{"id":266926148,"identity":"a503cf0f-6469-48ee-a586-7762f35ba9e1","order_by":2,"name":"Hamza K. Sabti","email":"","orcid":"","institution":"Republic of Iraq Ministry of Oil","correspondingAuthor":false,"prefix":"","firstName":"Hamza","middleName":"K.","lastName":"Sabti","suffix":""}],"badges":[],"createdAt":"2024-01-06 08:48:48","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3839295/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3839295/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":49761366,"identity":"261bea8c-0ef8-44f0-9156-2723604c8a13","added_by":"auto","created_at":"2024-01-17 15:59:50","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":18768,"visible":true,"origin":"","legend":"\u003cp\u003eExperimental setup.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-3839295/v1/b99643e27509cccca10999a0.png"},{"id":49762367,"identity":"a931ab4a-3097-4505-a4cb-4a472f508f3e","added_by":"auto","created_at":"2024-01-17 16:07:50","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":660131,"visible":true,"origin":"","legend":"\u003cp\u003eMOcroscopic image of CS specimen (Mag.=1000) 1)before corrosion 2) corroded (0.5% NaCl), 3) after cathodic protection by Zn (0.5% NaCl, 100 mm, PP=76%).\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-3839295/v1/cbb003e6294fce47558aca48.jpeg"},{"id":49761368,"identity":"c27b7188-85d0-44e4-9ddb-565b02d4a43d","added_by":"auto","created_at":"2024-01-17 15:59:50","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":414007,"visible":true,"origin":"","legend":"\u003cp\u003eProtection potential vs time when Zn is the sacrifical anode.\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-3839295/v1/4ae68ebcf517a13f7a3da55f.jpeg"},{"id":49761369,"identity":"7fbda26f-bf3c-469a-8d7b-6db068963d04","added_by":"auto","created_at":"2024-01-17 15:59:50","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":291430,"visible":true,"origin":"","legend":"\u003cp\u003eProtection potential vs time when Mg is the sacrifical anode.\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-3839295/v1/f60ae88d81ab398310749fba.jpeg"},{"id":49761367,"identity":"22264312-6aed-4b8d-b08a-e424a56e19a9","added_by":"auto","created_at":"2024-01-17 15:59:50","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":313237,"visible":true,"origin":"","legend":"\u003cp\u003eProtection current vs time for Zn anode\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-3839295/v1/8e7144a9158c5571a18a3493.jpeg"},{"id":49761371,"identity":"8d2c2df5-abf3-4341-a31a-aefbafc684b4","added_by":"auto","created_at":"2024-01-17 15:59:50","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":263612,"visible":true,"origin":"","legend":"\u003cp\u003eProtection current vs time foe Zn anode\u003c/p\u003e","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-3839295/v1/213410f53cb6ab330caf7e82.jpeg"},{"id":51611620,"identity":"588cde30-1407-4777-9709-43ff9233399c","added_by":"auto","created_at":"2024-02-25 22:37:41","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":769248,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3839295/v1/3678d55d-1533-4088-992d-68a4be873e60.pdf"}],"financialInterests":"","formattedTitle":"Cathodic protection of carbon steel using zinc and magnesium as sacrificial anodes in different conductivity solutions","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eCorrosion is the most destructive reaction of metals used in industry including petroleum industry as the corrosion reaction is considered a spontaneous reaction when appropriate conditions are available. According to recent reports the global cost of corrosions is around US\u003cspan\u003e$\u003c/span\u003e 2.5 trillion, which should be reduced by using different corrosion control methods [Loto et al, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Hu et al, 2022]. Cathode protection (CP) method is widely used in the oil and gas industry in order to prevent (or reduce) rust and corrosion of metal pipelines, tanks, and equipment. Underground pipes and tanks have been used worldwide for the transfer and storage of water, oil, gas, and other chemicals. Corrosion-related damages of these structures can lead to spoil of products, soil pollution, and environmental degradation.\u003c/p\u003e \u003cp\u003eCathodic protection (CP) by sacrificial anodes has numerous applications in practice especially in petroleum industry such as protection of: internals of water storage tanks, internals of fuel storage tanks, tank bottom, tank base from soil side, underground pipelines, internals of heat exchanger shells, ships, and others. Sacrificial anode cathodic protection is summarized by applying a potential more negative than \u0026minus;\u0026thinsp;850 millivolts versus copper/copper sulfate electrode. This potential is able to ensure the corrosion of metal almost zero in pH around 7 [Bahadori, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Ameh, et al, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2017\u003c/span\u003e, Gao et al, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2022\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe problem in sacrificial anode method is the instability of anode and the probability of fast consumption be the corrosive environment. However, the sacrificial anode cathodic protection has several advantages such as it does not need external power source, can be installed easily, and low maintenance cost [Prasad et al, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2021\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe cathodic protection by the sacrificial anode includes the use of high negativity metal (the anode) which ensures potential of more negative than \u0026minus;\u0026thinsp;0.85 V (vs. Cu/CuSO4) of the structure. This technique is used in limited areas and close distances, as the sacrificial anode cannot produce protection currents over long distances, because the protection voltage decreases when the structure to be protected moves away from the sacrificial anode due to the resistance polarization [Bhuiyan et al, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2019\u003c/span\u003e, Wang et al, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2020\u003c/span\u003e]. The distance at which the sacrificial anode is effective is dependent on the electrochemical properties of anode, the resistivity of the medium, the size of the anode, and chemicals present in the medium.\u003c/p\u003e \u003cp\u003eZinc and Magnesium are the most competitive used metals as sacrificial anodes due to their high electrochemical activity [ Hasan and Aziz, 2017; Khadom, 2002; Yang et al, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2023\u003c/span\u003e]. Despite many years of research, their performance in certain environments is still not well understood, needing further investigation. In addition, the consumption rate of these sacrificial anodes is dependent on the nature of the corrosive medium [Khodary et al, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2019\u003c/span\u003e] and it needs to be evaluated at the operating conditions. The objective of this work is to investigate the effect of solution conductivity on the optimum cathodic protection conditions regarding the anode to cathode distance and area ratio (AR) using zinc and magnesium anodes. In addition, it is aimed to compare the efficiency of Zn and Mg under different operating conditions.\u003c/p\u003e"},{"header":"2. Experimental work","content":"\u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the experimental setup which comprises a water bath, digital voltmeter to measure the structure potential, ammeter to measure the current, saturated calomel electrode (SCE) as a reference electrode, and heater and controller to set the required temperature. Digital balance of high accuracy (4 decimal places of a gram) to measure the weight loss. Optical Microscope (type of KRUS/ Germany) was used for surface inspection after corrosion and after applying cathodic protection. Pure zinc (sheet) and pure magnesium (strip) were used as a sacrificial anode. Three different NaCl solutions were used (0.5%, 1%, 3.5% wt.%) at 30 \u003csup\u003eo\u003c/sup\u003eC. The carbon steel specimen used was a cylindrical rod with dimensions of 150 mm long and 10 mm in diameter. The zinc specimen sheet dimensions were 45\u0026times;45\u0026times;1.4 mm and of Mg strip were 200\u0026times;140 mm. Three values of anode to cathode distance were investigated namely, 100, 200, 300 mm and different values of anode to cathode area ratios (AR).\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eAt first, the free corrosion rates were determined for different conditions. The specimen is prepared in several steps starting from the sanding process, which includes the use of emery papers in several degrees: 120, 400, 600, and 2000 to obtain a clean surface free of dirt. After that, the specimen was washed with distilled water several times and then dried with a clean tissue, after which it is placed in acetone for three minutes to remove the deposits if any. In the next step, the specimen was washed with distilled water, then dried with a clean tissue and heated in an oven at 80 \u003csup\u003eo\u003c/sup\u003eC for 5 minutes. The specimen was then stored in a vacuum desiccator over a high activity silica to preserve it from humidity until use. The specimen was then weighed to measure the initial weight. The salt solution is prepared from sodium chloride in different concentrations (0.5%, 1%, 3.5% wt). At each concentration, the specimen is immersed in the solution and left for four hours to experience corrosion, where the specimen is submerged at a depth of 80 mm below the surface. After the end of the specified time, the specimen is extracted, washed with distilled water, then cleaned with a smooth plastic brush, to remove corrosion product layer well, then was dried with a clean tissue, immersed back in acetone for three minutes, washed again with distilled water, dried and weighed to obtain the weight loss. When applying the cathodic protection (CP) the same procedure is followed to obtain the weight loss in the presence of CP. The corrosion rate is obtained using to the following equation [Kilbane, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Ali and Hasan, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2020\u003c/span\u003e]:\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\text{C}\\text{R} \\left(\\text{i}\\text{n} \\text{g}\\text{m}\\text{d}\\right)=\\frac{\\text{w}\\text{e}\\text{i}\\text{g}\\text{h}\\text{t}\\text{l}\\text{o}\\text{s}\\text{s}\\left(\\text{g}\\right)}{\\text{A}\\text{r}\\text{e}\\text{a}\\left({\\text{m}}^{2}\\right)\\times \\text{T}\\text{i}\\text{m}\\text{e} \\left(\\text{d}\\text{a}\\text{y}\\right)}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u0026hellip;\u003c/p\u003e \u003cp\u003eWhere CR represents corrosion rate in g/m\u003csup\u003e2\u003c/sup\u003e.d (gmd). The protection percent (pp) was calculated as:\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\text{P}\\text{P}\\text{\\%}=\\left(\\frac{\\text{C}{\\text{R}}_{0}-\\text{C}\\text{R}}{\\text{C}{\\text{R}}_{0}}\\right)\\text{X} \\text{l}00$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u0026hellip;\u0026hellip;..\u0026hellip;\u0026hellip;..\u003c/p\u003e \u003cp\u003eCR\u003csub\u003e0\u003c/sub\u003e and CR are the corrosion rates in absence and in presence of sacrificial anodes respectively.\u003c/p\u003e \u003cp\u003eIn sacrificial anode experiments, the NaCl solution was prepared and heated in the plastic water to constant temperatures of 30 \u003csup\u003eo\u003c/sup\u003eC. Then, the specimen was immersed and the electrical circuit was switched on. The current and voltage was recorded with time until the end of test duration. The structure potential was measured versus standard calomel electrode (SCE). The capillary tube was placed at a distance of 2 mm from the specimen and connected to the calomel electrode to measure the specimen potential. The specimens\u0026rsquo; analyses are shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e to \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e as analyzed in Material Research Center/Ministry of Sciences and Technology. Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e lists the solutions electrical conductivity as measured experimentally using conductivity meter.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCarbon steel Chemical Composition\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"11\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElements\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFe\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ePb\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eS\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eNi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eMo\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"4\" rowspan=\"5\"\u003e \u003cp\u003eWeight%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e98.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLess than 0.0005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLess than 0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLess than 0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.510\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eLess than 0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.0340\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.202\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eLess than 0.0005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e0.0107\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eAl\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eAs\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eCu\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eBi\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003eSe\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003eZr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003eCo\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003eTi\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u003cb\u003eV\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u003cb\u003eW\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0283\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLess than 0.0005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.0464\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLess than 0.0015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLess than 0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.0026\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eLess than 0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.0011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0.0012\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e0.0081\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eZn\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eCr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eAs\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eCa\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003eNb\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003eSb\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003eTa\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c11\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0036\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.165\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLess than 0.0005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLess than 0.0005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLess than 0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eLess than 0.005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.0126\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c11\" namest=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eZinc Chemical Composition\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElements\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eZn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePb\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ePb\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eFe\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eNi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSi\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"4\" rowspan=\"5\"\u003e \u003cp\u003eWeight%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e99.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.0046\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.0024\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.0046\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.0009\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eLess than 0.002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.0072\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.0009\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eAl\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eCd\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eCu\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eBi\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003eAg\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003eHg\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003eln\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003eTl\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0051\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.0013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.0063\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.0002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.0001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.0006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.0001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.0012\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eMg\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eCr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eAs\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eSb\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c9\" namest=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLess than 0.0005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.0001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLess than 0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c9\" namest=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMagnesium Chemical composition\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"11\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElements\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMg\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePb\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ePb\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eFe\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eNi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eCe\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eDy\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"6\" rowspan=\"7\"\u003e \u003cp\u003eWeight%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e99.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.170\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLess than 0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.0046\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLess than 0.002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eLess than 0.002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eLess than 0.0002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eLess than 0.0005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eLess than 0.025\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eLess than 0.005\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eAl\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eCd\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eCu\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eBi\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003eAg\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003eHg\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003eln\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003eHo\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u003cb\u003eEr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u003cb\u003eGd\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.0009\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.0002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLess than 0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.0006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.0001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eLess than 0.005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eLess than 0.005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eLess than 0.005\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eMg\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eCr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eAs\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eCa\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003eBe\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003eFe\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003eZn\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003eSr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u003cb\u003eLa\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u003cb\u003eLu\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLess than 0.0005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.0001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLess than 0.0001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.0001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.0161\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.0011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.0001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eLess than 0.002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eLess than 0.0005\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eNd\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003ePr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eSm\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eTb\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003eTh\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003eTm\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003eY\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cb\u003eYb\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u003cb\u003eZr\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e\u003cb\u003eLi\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLess than 0.025\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLess than 0.015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLess than 0.005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLess than 0.0002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLess than 0.025\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eLess than 0.005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eLess than 0.005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eLess than 0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eLess than 0.0025\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eLess than 0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eNaCl Solution conductivity [Widodo et al, 2018]\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNaCl concentration, wt%\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eConductivity, mS/cm\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e18.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e32.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e95.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"3. Result and discussion.","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Free corrosion\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe free corrosion rate, before applying cathodic protection, was determined by measuring the weight loss in different conductivity solutions as listed in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. At low concentration (0.5%), the corrosion rate is low, with the increase in the concentration of salt to 1%, the corrosion rate increases appreciably due the increased conductivity. At highest concentration it increases little further. The high concentration of NaCl causes a decrease in dissolved oxygen concentration and a formation of effective corrosion leading to restrain the corrosion attack [Revie and Uhlig, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2008\u003c/span\u003e, Slaiman and Hasan, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2010\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCorrosion rate of CS in different NaCl Solutions\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNaCl Concentration\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003egmd\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e8.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e14.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e15.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Cathodic Protection by Zinc Anode\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eTables\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e through \u003cspan refid=\"Tab8\" class=\"InternalRef\"\u003e8\u003c/span\u003e list the values of corrosion rates of CS for different experimental conditions under the application of cathodic protection by zinc anode. Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e for cathodic protection in 0.5% NaCl solution shows that for 5% area ratio of Zn anode to structure (CS) the cathodic protection reaches 76% at the shortest distance between anode and structure (100 mm). When the distance is increased to 3 times (to 300 mm apart), the CP decreases to 58%; i.e. decrease by about 14%. For area ratio (AR) of 17%, the CP is 100% at distance 100 mm and 95% at 300 mm. The decrease in CP with distance is ascribed to the increased solution resistance to current flow which causes a potential drop leading to a departure from the protection potential. It is evident that the 17% area ratio gives higher CP than 5% for all distances. 100% protection is attained at a distance of 100 mm indicating no need to go for a higher area ratio. Increase in protection percent with anode to cathode area ratio has also been reported by Hamad [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2015\u003c/span\u003e]. The larger the area of zinc, the better the protection because the large area provides more electrons that are more uniformly distributed on the steel surface [Loto and Popoola, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2011\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab7\" class=\"InternalRef\"\u003e7\u003c/span\u003e for cathodic protection in 1% NaCl, the same trend of CP for the case of 0.5% with distance and with aera ratio is noticed. However, the cathodic protection is generally high than the case of 0.5%. The same behavior is true for case of 3.5% as shown in Table\u0026nbsp;\u003cspan refid=\"Tab8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. Accordingly, no systematic trend of CP efficiency with salt concentration or solution conductivity can be noticed in present work. The higher the salt concentration or higher medium conductivity is the better the flow of protection current that causes a reduction of O2 on the cathode surface leading to better protection. However, the more corrosive medium can cause faster damage to the anode due to higher consumption rate leading to reduce the efficiency of protection. Additionally, when the effectiveness of the anode decreases with time, the structure starts to corrode and a thin film of corrosion product layer forms which may reduce the corrosion rate [Su et al, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2023\u003c/span\u003e, Yang et al, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2023\u003c/span\u003e] or enhance it by increasing the turbulence at the surface at flow conditions [Slaiman and Hasan, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2010\u003c/span\u003e]. All these factors make the behavior of CP percent with time more complicated.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e presents microscopic images of CS specimens before exposure to corrosive solution, after exposure to corrosive solution, and after applying cathodic protection by Zn anode. It is evident that after corrosion there is a clear corrosion damage on the surface image 2. When using cathodic protection, the surface is less corroded as shown in image 3.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCorrosion rate and cathodic protection percent using Zn for the parameter range investigated at NaCl concentration of 0.5%.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eConcentration of NaCl\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDistance, mm\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCP%\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003e0.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.096\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e76%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.205\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e64%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.699\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e58%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e17%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.247\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e97%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.370\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e95%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab7\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 7\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCR rate and cathodic protection percent using Zn for the parameter range investigated at NaCl concentration of 1%.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eConcentration of NaCl\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDistance, mm\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCP%\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003e1%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.481\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e91%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.562\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e73%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5.548\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e67%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e17%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.247\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e98%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.123\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e98%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab8\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 8\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCR rate and cathodic protection percent using Zn for the parameter range investigated at NaCl concentration of 3.5%.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eConcentration of NaCl\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDistance, mm\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCP%\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003e3.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e76%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e75%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e72%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e17%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Cathodic Protection by Magnesium\u003c/h2\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab9\" class=\"InternalRef\"\u003e9\u003c/span\u003e through \u003cspan refid=\"Tab12\" class=\"InternalRef\"\u003e11\u003c/span\u003e presents the values of cathodic protection percent using Mg anode for different salt concentrations, area ratios, and cathode to anode distance. For 0.5% NaCl solution, the cathodic protection percent for 17% Mg to structure area ratio is 50% at distance 100 mm decreasing to 40% at distance 300 mm. This means increasing the distance 3 times causes a decrease in CP by about 20%. The CP for 34% AR, the relevant values increases to 79% and 58%, i.e. increasing the distance 3 times causes a decrease in CP by 16.6%. Table\u0026nbsp;\u003cspan refid=\"Tab10\" class=\"InternalRef\"\u003e10\u003c/span\u003e for NaCl concentration of 1%, reveals the same behavior of 0.5% NaCl with higher CP percent. For the case of 3.5% NaCl solution shown in Table\u0026nbsp;\u003cspan refid=\"Tab12\" class=\"InternalRef\"\u003e11\u003c/span\u003e, the CP % is much lower than that of 0.5% and 1% indicating that the Mg anode provides poor protection in high salt media. This is ascribed to the occurrence of severe free corrosion of Mg in 3.5% NaCl solution because the lifespan of Mg in this corrosive solution is too short. Table\u0026nbsp;\u003cspan refid=\"Tab9\" class=\"InternalRef\"\u003e9\u003c/span\u003e indictates also that increasing the area ratio of Mg from 17\u0026ndash;34% causes an increase in cathodic protection percent by 45 to 60 percent depending on the distance between anode and cathode. The same behavior is true for Tables\u0026nbsp;\u003cspan refid=\"Tab10\" class=\"InternalRef\"\u003e10\u003c/span\u003e and \u003cspan refid=\"Tab12\" class=\"InternalRef\"\u003e11\u003c/span\u003e. Close behavior has also been observed by Loto et al, [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2019\u003c/span\u003e] for Mg anodes in 0.5M HCl.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab9\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 9\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCR rate and cathodic protection percent using Mg for the parameter range investigated at NaCl concentration of 0.5%.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eConcentration of NaCl\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDistance, mm\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCP%\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003e0.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e17%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e50%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e45%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e40%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e34%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e79%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e66%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e58%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab10\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 10\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCR rate and cathodic protection percent using Mg for the parameter range investigated at NaCl concentration of 1%.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eConcentration of NaCl\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDistance, mm\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCP%\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003e1%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e17%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e69%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e66%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e63%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e34%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e79%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e67%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e62%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab11\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 11\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCR rate and cathodic protection percent using Mg for the parameter range investigated at NaCl concentration of 3.5%.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eConcentration of NaCl\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDistance, mm\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCR, gmd\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCP%\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e \u003cp\u003e3.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e17%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e73%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e69%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e57%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003e34%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e73%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e54%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e49%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Consumption rate of the anodes\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eTable\u0026nbsp;12 presents the consumption rate (expressed by corrosion rate unit g/m\u003csup\u003e2\u003c/sup\u003e.day) of of Mg and Zn when used as sacrificial anodes to protect carbon steel in different NaCl concentartions. It can be seen that the corrosion rate of Mg is higher than Zn although Zn gives higher protection perecent. This indicates that the use of Zn is more successful than Mg in the range of solutions conductivites investigated in this work. This agrees with the findings of Sadawy et al. [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2020\u003c/span\u003e]. The high activity of Mg, increases its corrosion in salt solutions leading to a decrease in its activity and surface area with time.\u003c/p\u003e \u003cp\u003eThe consumption of Zn and Mg is due to the anodic dissolution that provide the requred currents to portect the CS as follows:\u003c/p\u003e \u003cp\u003eZn\u0026thinsp;=\u0026thinsp;Zn\u003csup\u003e2+\u003c/sup\u003e+ 2e (1)\u003c/p\u003e \u003cp\u003eMg\u0026thinsp;=\u0026thinsp;Mg\u003csup\u003e+\u003c/sup\u003e+ 2e (2)\u003c/p\u003e \u003cp\u003eThe liberated electrons will flow through the connection were to be used up on the cathode surface in oxygen reduction reaction leading avoide ther reaction of iron with O\u003csub\u003e2\u003c/sub\u003e, i.e, restrain the corrosion of carbon steel. The cathodic reaction on the steel surface is:\u003c/p\u003e \u003cp\u003eO2\u0026thinsp;+\u0026thinsp;2H\u003csub\u003e2\u003c/sub\u003eO\u0026thinsp;+\u0026thinsp;4e\u0026thinsp;=\u0026thinsp;4OH\u003csup\u003e\u0026minus;\u003c/sup\u003e (3)\u003c/p\u003e \u003cp\u003eThe consumption rate of the used anodes is influenced by solution conductivity, the distance between anode and structure, and the deposits formed on anode surface which influence its activity. Table\u0026nbsp;12 indicates no systematic trend of the consumption rate of anodes with salt concentration or with cathodic protection percent which can be attributed to the complicated phenomena occurring on anode and cathode surfaces. Khodary et al, [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2019\u003c/span\u003e] reported slight increase in Zn consumption rate with the NaCl solution for a long time when used to protect CS.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab12\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 11\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCorrosion rate of anodes used versus protection attained\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eNaCl concentration\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eCR (gmd)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eCPP\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eZinc\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003eArea ratio 5%\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eMg\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003eArea ratio 17%\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eZinc\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eMg\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4.44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e76%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e50%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e91%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e69%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e76%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e73%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Protection potentials\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003e presents the typical trend of protection potential versus time for Zn anode at different conditions. It can be noted that for small distance (100 mm), the protection potential is very stable indicating efficient anode performance. The same observation was reported by previous investiagtors [Loto and Popoola, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; So et al, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2023\u003c/span\u003e]. However, there is a slight shift to more positive direction for distance beyond that but the potential is still more negative than \u0026minus;\u0026thinsp;0.9 V (SCE) which provides good protection. This explains the high cathodic protection percent for zinc shown in Tables\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e to \u003cspan refid=\"Tab8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. Figure\u0026nbsp;4 shows the typical trend of protection potential with time when using Mg as a sacrificial anode. It can be seen that the structure potential shifts sharply to more positive at the initial period of cathodic protection application. Within about 25 min, the potential changes by about 63% to more positive reaching potenatials of -0.6 to -0.5 V (SCE) indicating the corrosion zone. Similar behavior of zinc consmption rate has been reported by Ziadane et al [2018] when protecting CS tanks against hot corrosion.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.6 Protection currents\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eFigures \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e shows the trend of protection currents with time for Zn and Mg, respectively, for different anode to cathode distances. The protection current requirement is the amount of current needed to achieve full cathodic protection to the structural surface [Brondel, et al, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1994\u003c/span\u003e; Bhuiyan et al, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2019\u003c/span\u003e]. It can be noticed that the protection current decreases with time for all the distance. This can be attributed to a decrease in the efficiency of the sacrificed anode with time due to the potential shift toward more positive, which makes it unable of providing the required protection current for the full protection [Meredith, 1989; Hasan and Abdul-Jabbar; \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2011\u003c/span\u003e, Lotto and Popoola, 2011].\u003c/p\u003e \u003cp\u003eFor Mg, it can be seen that the protection current is initially very high (much higher than Zn current) but it drops sharply at the first 60 minutes of the run reaching almost zero current. This means that for the remaining 3 hours of experiment, the Mg is no longer working. Due to high potential drop and high consumption rate of Mg due to the large polarization the current decreases appreciably leading to a poor protection after a short time. The high reduction in the protection current with time is ascribed to the fast dissolution of magnesium anodes in salty solution which reduces the area of the anodes as has been seen by visual observation in this work.\u003c/p\u003e \u003c/div\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe mechanism of cathodic protection of the current system can be explained briefly. When the current is imposed by connecting the structure (CS) to the scarifying active anode, the flow of electrons through the wire reduces the dissolved O\u003csub\u003e2\u003c/sub\u003e on the structure surface leading to form hydroxyl ion as in Eq.\u0026nbsp;(3). Therefore, instead of O\u003csub\u003e2\u003c/sub\u003e reaction with iron, it reacts with electrons leading to avoid or reduce the corrosion [Hasan \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2014\u003c/span\u003e]. At the anode (Zn on Mg) the anodic reaction occurs according to Eq.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) or (2). When the activity of anodes decreases with time, its ability to shift the CS potential to more negative decreases leading to a shift in the potential to more positive as shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003e. When the CS becomes more positive than \u0026minus;\u0026thinsp;0.85 vs (SCE), the CS starts to undergo corrosion damage. The rate of corrosion depends on the departure of potential from the protection potential. The higher the potential departure, the higher the corrosion rate of the structure. That is why the corrosion rate of the structure (CS) when using Mg is generally higher than that when using Zn even when using a high area ratio of Mg. Number of authors [Freiman and Kuznetsova, 2001; Leeds, 2007; Kajiyama and Okamura, 1999; Angst et al, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2016\u003c/span\u003e] reported that the cathodic protection of steel is attained by increasing the pH at the structure surface due to formation of OH\u003csup\u003e-\u003c/sup\u003e. In several situations the formation of film close to the metal surface causes an increase in the pH which favors the passivation of steel and therefore, it provides protection from further corrosion attack [Angst et al, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2016\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThe use of Zn and Mg for cathodic protection (CP) of carbon steel in different NaCl solutions (0.5\u0026ndash;3.5% wt) revealed several conclusions. Zinc is generally successful in providing efficient protection for the range of NaCl concentration investigated. It can provide more than 95% protection when placed within 300 apart from the structure with an area ratio of 17%. In addition, its consumption rate is relatively low even at high salt concentration. The protection potential and currents of Zn are relatively stable for long time which provides a successful performance. The Mg anode is not effectively protecting the structure in this range of salt concentrations especially for long term protection. This is due to its fast depreciation leading to a shift in structure potential to more positive quickly. Even when using a large area ratio of Mg to steel, the protection efficiency is low. The protection current drops to almost zero after about 1 h of applying the CP. The protection potential shifts to more positive by 63% after about 25 min. Therefore, Mg is not recommended for high conductivity solutions. Increasing the area ratio of Zn to structure (CS) from 5\u0026ndash;17% caused an increase in the protection efficiency b 30%. The larger the distance between anode to cathode, the lower the cathodic protection efficiency. Increasing the distance between anode and structure from 100 mm to 300 mm, causes a decrease in cathodic protection percent by up to 22% for Zn and 22% for Mg depending on area ratio and solution conductivity.\u003c/p\u003e"},{"header":"Abbreviations","content":" \u003cp\u003eAR area ratio\u003c/p\u003e \u003cp\u003eCP cathodic protection\u003c/p\u003e \u003cp\u003eCR corrosion rate\u003c/p\u003e \u003cp\u003eCS carbon steel\u003c/p\u003e \u003cp\u003egmd gram/m\u003csup\u003e2\u003c/sup\u003e. day\u003c/p\u003e \u003cp\u003ePP protection percent\u003c/p\u003e \u003cp\u003eSCE standard calomel electrode\u003c/p\u003e \u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eConflict of interest:\u003c/strong\u003e On behalf of all the authors of this article, the corresponding author confirm that there is no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBasim O. Hasan: proposed the idea, wrote the discussion and reviewed the whole manuscript, Amel A. Beden: carried out the experimental measurements, Hamza K. Sabti, installed the rig, wrote part of the discussion, and editing.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAli ME, Hasan BO (2020) Galvanic corrosion of carbon steel under concentration cell formation in MgCl. Solut as Inorg pollutant effect flow velocity Corros Reviews 38(3):287\u0026ndash;298\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAmeh ES, Ikpeseni2 SC, Lawal LS (2017) A Review of Field Corrosion Control and Monitoring Techniques of the Upstream Oil and Gas Pipelines. 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Mater Corros 67:11\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBahadori A (2014) Cathodic Corrosion Protection Systems: A Guide for Oil and Gas Industries, 1st Edition, Gulf Professional,\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBhuiyan S, Law D, Ward L, Saliba J (2019) The effects of anode distance and corrosion activity on current distribution for ICCP systems, MATEC Web Conf., vol. 289, p. 03001, 2019\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBrondel D, Edwards R, Hayman A, Hill D, Semerad T (1994) Corrosion in the Oil Industry, pp. 4\u0026ndash;18\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFreiman, L. I., E. G. Kuznetsova (2001), Model Investigation of the Peculiarities of the Corrosion and Cathodic Protection of Steel in the Insulation Defects on Underground Steel Pipelines, Prot. 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Int J Electrochem Sci 13:29\u0026ndash;44\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSo Y, Park E-H, Kim J-G (2023) Effect of Zinc Addition in Filler Metal on Sacrificial Anode Cathodic Protection of Fin-Tube Aluminum Heat Exchanger. J Electrochem Sci Technol, Epub ahead of print,\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"cathodic protection, sacrificial anode, zinc, magnesium, anode consumption","lastPublishedDoi":"10.21203/rs.3.rs-3839295/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3839295/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis work investigated the cathodic protection of carbon steel in different conductivity solutions using sacrificial anodes of zinc and magnesium. The effect of salt concentration (0.5\u0026ndash;3.5% NaCl), the distance between structure and anode, and the area ratio of anode to cathodic on the protection efficiency was investigated and discussed. The consumption rate of sacrificial zinc and magnesium was evaluated for a range of operating conditions. High cathodic protection efficiency was obtained by Zn with low consumption rate compared to Mg. The Mg showed short lifespan and high potential shift to more positive and high protection current decrease after short time of applying the protection. Therefore, zinc is a successful sacrificial anode while magnesium is not recommended for long term protection for the range of salt concentrations investigated.\u003c/p\u003e","manuscriptTitle":"Cathodic protection of carbon steel using zinc and magnesium as sacrificial anodes in different conductivity solutions","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-01-17 15:59:45","doi":"10.21203/rs.3.rs-3839295/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"76e521b9-d608-4e0a-9880-1501e60838aa","owner":[],"postedDate":"January 17th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-02-25T22:29:33+00:00","versionOfRecord":[],"versionCreatedAt":"2024-01-17 15:59:45","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3839295","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3839295","identity":"rs-3839295","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}