Improving the Final Atmospheric Seal of Conserved Archaeological Iron from Marine Sites

Improving the Final Atmospheric Seal of Conserved Archaeological Iron from Marine Sites | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Improving the Final Atmospheric Seal of Conserved Archaeological Iron from Marine Sites Christopher Dostal This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4468228/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 The conservation of iron artifacts from marine archaeological sites faces the persistent challenge of electrochemical corrosion post-recovery. Traditional conservation methods, such as electrolytic reduction and chemical stabilization, have been very successful in stabilizing these artifacts, but post-treatment, can do little to provide durable long-term protection when exposed to atmospheric conditions. This study investigates the efficacy of a novel conservation treatment that combines microcrystalline wax with a paint overlay, aimed at improving the final atmospheric seal of conserved iron artifacts. Conducted at the Conservation Research Laboratory (CRL) at Texas A&M University, the experiment involved treating two historically significant cannons with this dual-layer method. The cannons were subjected to rigorous environmental conditions to test the durability and protective quality of the treatment. Results indicate that the combined use of microcrystalline wax and paint not only enhances the corrosion resistance of iron artifacts but also maintains aesthetic and structural integrity under variable climatic exposures. This paper discusses the experimental procedures, findings, and the practical implications of this treatment, advocating for its application in both museum settings and outdoor displays. The study contributes a significant advancement to conservation practices, offering a reversible, effective solution that upholds the artifact's historical value while extending its lifespan. Conservation Electrolysis Surface Coatings Curation Marine Sites Iron Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction Maritime archaeologists have long been forced to grapple with the cruel reality of electrochemical corrosion of iron artifacts from shipwrecks and other submerged sites. Iron is the constituent component of a host of materials found on ships, from cannons to anchors to the ships stove, to rigging elements to ammunition. The post-depositional environment of any marine archaeological site is dynamic and varied, but the one inevitably reliable through line is the encrustation and corrosion of iron materials. The journey from the encrusted conglomerate that arrives at the lab to the clean, conserved material that leaves is incredibly satisfying to behold, but the processes of corrosion do not end when the objects leave the lab, and as such a re-evaluation of the final sealant that impacts the rate of future corrosion is warranted (Fig. 1 ). The mechanism for corrosion of wrought and cast-iron archaeological materials in marine environments sites is well-understood [ 1 , 3 , 6 , 10 ]. Additionally, though there are varying degrees of consensus, there are several widely accepted conservation processes to stabilize archaeological iron, including chemical reduction, electrolytic reduction, and chemical cleaning [ 5 , 6 , 9 ]. A significant amount of scholarship has been dedicated to these two aspects of iron conservation, but there has been little done on the assessment of the final step of the conservation treatment, the sealant applied to the object to inhibit future corrosion. This paper addresses a series of recent experiments undertaken to improve the final atmospheric seal of conserved iron. At the Conservation Research Laboratory (CRL) at Texas A&M University, per the guidelines established by Hamilton [ 6 ], the vast majority of iron archaeological materials from marine sites are treated via electrolysis after mechanical deconcretion. Electrolysis is typically undertaken with three stages of current density: 0.001–0.005 amp/cm 2 to reduce ferrous corrosion compounds (Fe 2+ ) to a more stable, metallic-like state of magnetite (Fe 3 O 4 ) 0.05 amp/cm 2 for chloride removal 0.1 amp/cm 2 for mechanical cleaning via the evolution of hydrogen on the surface of the metal [ 6 , 9 ]. Note that the higher current density is only carried out if the underlying metal is sturdy enough to withstand the enhanced hydrogen evolution. Once reduction is complete and the chloride concentration is stable and low in the solution (< 10ppm as analyzed via mercuric nitrate (Hg(NO 3 ) 2 ) titration), the objects are removed from the electrolysis vat and placed in a series of boiling deionized water baths to remove residual electrolyte until the pH stabilizes. At this stage, historical cast or wrought iron is composed of a composite mix of graphite, metallic iron, and reduced iron corrosion in the form of magnetite. With the hot water from the rinse promoting electron exchange from the anodic graphite to the cathodic metallic iron, the surface of the object will begin corroding again immediately upon removal from the water [ 9 ]. To limit this post-boil corrosion, the galvanic cell must be interrupted by either removing the oxygen or the electrolyte, in this case, water. Removing the oxygen from the room tends to be detrimental to the productivity of the conservators, so instead either the water must be removed or a surface coating applied to block the oxygen. North [ 9 ] recommends solvent dehydration via acetone submersion for cast iron objects, though in practice, this is not practical for substantial artifact assemblages or for very large objects like cannon or anchors. In lieu of this, the CRL utilizes dewatering via submersion in molten microcrystalline wax, as outlined below. As soon as an object is removed from the boil, three coats of 20% technical grade tannic acid in deionized water and ethanol are applied via brushing (Fig. 2 ). (For large cannons, we use tennis balls screwed to a long piece of bamboo to paint the bore). The tannic acid forms a corrosion inhibiting barrier of ferric tannate (Fe 2 (C 14 H 7 O 9 )(OH) 3 ) on the surface [ 7 , 8 , 11 ]. There are several commercial corrosion resistant coatings available, and through experiments we have found them to be equally effective, but not as aesthetically pleasing. Once the tannic acid coats are dry, the final stage is the atmospheric sealant. For this, there are two broad options: either some kind of wax barrier, or a paint covering. In practice, the application of microcrystalline wax has proven to be the most effective option for long term preservation, which is likely linked to the typical method of application. Unlike painting, which is a surface application, wax is applied by submersing the artifacts in 175°C wax until all residual moisture is driven from the object. Then the wax is cooled to ~ 100°C and the artifact is removed (Fig. 3 ). Crucially, driving the moisture out and replacing it with wax significantly limits potential electrolyte for future corrosion. Objects that are either too large to immerse in wax or objects that will be stored outdoors or in areas where they will be in contact with the public are generally sealed with paint, as it provides a more durable barrier from physical contact and is more resistant to the elements. Even so, painted objects tend to produce more visible corrosion more quickly after conservation due to the aforementioned residual moisture. Apart from the differences in efficacy, the reversibility of each sealant is a factor. Reversability is a cornerstone of archaeological conservation ethics, and unless absolutely necessary, all methodologies and chemicals used should be reversible [ 12 , 15 ] Microcrystalline wax of similar formulations to the one used by CRL conservators is easily one of the most reversable sealants, because with a melting point of 86.4°C, it can removed by simply submerging the object in boiling water, or removed with a heat gun [ 13 ]. Certain paints are easier to remove than others, though most tend to be emulsions which once dry, require a mixture of solvents to remove. Some paints are not readily soluble in solvents at all, though most can be removed with either a poultice of sodium hydroxide (NaOH) or mechanically by scraping or with a pressure washer if the underlying metal is sturdy enough. Previously, publications and conversations about final sealants have been centered on using wax, paint, or some other sealant, often experimental in nature. Generally, the consensus reflects what is stated above, that wax coatings are preferred, but not suitable for outdoor display [ 2 , 4 , 8 14 ]. It has also been long held anecdotally that you cannot paint over an object treated with wax, because at warmer temperatures the wax will melt, loosening the paint. Through a happy accident, the CRL has discovered that not only is this not true, but when possible, combining microcrystalline wax and paint provides the benefits of both treatments with no discernable drawbacks. Methods/Experimental In June of 2021, the Louisiana Department of Culture, Recreation and Tourism, Office of Cultural Development, Division of Archaeology contracted with the CRL to conserve two cast iron cannons recovered in New Orleans. One of the cannons was an 18-pdr carronade, the other was labelled as a 6-pdr, but subsequent analysis revealed it to be a Blomefield pattern 9pdr. Per the original agreement, the cannons were to be sealed with microcrystalline wax, with the explicit wording from the CRL contract stating that “this finish coating is suitable for indoor museum displays, but will not survive the outside elements”. Both cannons were mechanically cleaned and then put through the electrolytic reduction process from June of 2021 to January of 2022. In January and February, the cannons underwent extensive boiling rinses in deionized water and were given three coats of tannic acid, then sealed with microcrystalline wax via submersion. In May of 2022, after the removal from wax, the Louisiana State Archaeologist indicated to the CRL that there had been a change of plans, and that the Blomefield 9pdr was going to be displayed outside of the Maritime Museum Louisiana in Madisonville, LA. Concerned that in the summer heat of Louisiana the wax would become tacky and wear off, we decided that the cannon would need to be painted. Instead of proceeding with the removal of the wax by re-boiling the cannon, we requested to conduct an experiment to determine if the wax actually needed to be removed. We took a rusty cast iron floor drain grate, ran it through ER, coated it in tannic acid, submerged it in molten microcrystalline wax, and then painted it with the standard paint the CRL uses for outdoor artillery and anchor displays. 1 Then the grate was placed outside and allowed to sit from May to June, where it was exposed to sustained high temperatures of 100–102°F. Even on the hottest days, there was no loosening of the adhesion, and the grate remained in superb condition. Given the results, we were given the go ahead to paint over the wax for both of the cannon in June of 2022. After returning both cannon to Louisiana, one of the cannon was placed in a curatorial space, and the other outside of the Maritime Museum Louisiana in Madisonville on March 22, 2023. Following the suggestions of the maintenance team from the National Parks Service Castillo de San Marcos in St. Augustine, Florida, we applied an undercoat of cherry-red paint followed by two coats of black paint. The black paint is generally accepted as the best way to present the color of cast and wrought iron, and the undercoat of cherry-red serves as a warning that the topcoats are getting worn or chipped. Benjamin Moore Super Spec™ HP D.T.M Alkyd Low Lustre paint, Black P23 80. Results and Discussion The drain grate continues its exposure to the elements as of this publication date. The summers of 2022 and 2023 in Bryan, Texas were exceptionally hot and dry, exposing the grate to extended periods of significant heat above 100°F, as well as multiple periods of hard-freeze weather (< 20°F), driving rains, hail, significant wind, etc. As of this writing, visual and physical inspection reveals no significant wear and no corrosion (the color of the paint has faded slightly). Assessment of the cannon has proven similarly positive results there. One year later, the Blomefield cannon outside of the Maritime Museum has no indication of corrosion, though there does appear to be some wear on the outermost layer of paint. Given that the cannon is positioned in an area that is accessible to the public, this is accepted as normal wear and tear as the cannon is touched. Given the positive results of the experiment and the resulting cannon treatments, the recommendation of the author is to combine microcrystalline wax with a suitable outdoor paint for the best results when conserving iron that will be displayed outdoors or will be potentially accessible by members of the public. The removal of residual moisture in the iron and replacing empty spaces in porous iron leads to longer lasting corrosion resistance, while the addition of the paint protects the wax and provides a stronger barrier against abrasions and wear that are inevitable for objects subjected to the elements or by over eager members of the public. Conclusions This study has demonstrated the efficacy of combining microcrystalline wax with paint as a conservation treatment for iron artifacts intended for outdoor display or interaction with the public. The experimental results from the application on both a test iron grate and two historic cannons have shown that this method offers superior preservation qualities under various environmental conditions, including extreme temperatures, precipitation, and mechanical wear. The success of this treatment is primarily attributed to the synergistic effect of microcrystalline wax and paint. The microcrystalline wax acts as a critical barrier to moisture, effectively limiting the electrolyte's presence necessary for corrosion processes. The subsequent application of paint not only enhances the aesthetic presentation of the artifacts but also provides an additional durable layer against physical damage and environmental exposure. This dual-layer approach not only preserves the integrity of the iron artifacts but also facilitates their maintenance, as indicated by the cherry-red undercoat's practical utility in monitoring wear and tear. While the findings of this study are promising, further research is necessary to determine the longevity of this treatment method as opposed to just wax or just paint. Because of the promising results from the Blomefield cannon, a second cache of cannon from the Savannah River are being treated with the same wax/paint combination. A follow-up study will be conducted in the coming years on both cannon groups to determine long term durability. The integration of microcrystalline wax and paint represents a significant advancement in the conservation of iron artifacts, particularly those exposed to outdoor environments or direct public interaction. This study's findings suggest that conservation practitioners should consider this method for its efficacy, practicality, and aesthetic benefits. Additionally, the reversibility of the treatment ensures that future conservation efforts can adapt to new technologies and methodologies without compromising the artifact's historical value. This research contributes to the broader field of archaeological conservation by offering a novel approach to preserving iron artifacts. It underscores the importance of interdisciplinary collaboration in developing conservation strategies that are both effective and respectful of historical integrity. As we move forward, it is crucial that conservation practices continue to evolve, incorporating both traditional knowledge and innovative technologies to protect our cultural heritage for future generations. Abbreviations CRL Conservation Research Laboratory Declarations This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Availability of data and materials : Not Applicable Competing interests : The author declares that they have no competing interests Funding : The conservation of the cannon came from the Louisiana Department of Culture, Recreation and Tourism, Office of Cultural Development, Division of Archaeology, and though that was the impetus for this project, they did not directly fund the experiment, analysis, or writing for this publication. Authors' contributions : CD is the sole author. Acknowledgements : Special thanks to Dr. Chip McGimsey, State Archaeologist, LA division of Archaeology for allowing us to proceed with the experiment. This work was facilitated by the exceptional staff conservators at the CRL who helped with these experiments, especially John Hamilton. Finally, a hearty thank you to Chloe Stephan at the Maritime Museum Louisiana, whose photos were crucial to this paper. Author Information: Chris Dostal is the director of the Conservation Research Laboratory and an assistant professor in the nautical archaeology program at Texas A&M University. References Angelini E, Grassini S, Tusa S. 2013. Underwater Corrosion of Metallic Heritage Artefacts. In Corrosion and Conservation of Cultural Heritage Metallic ArteFacts , by Watkinson, Angelini, and Adriens Dillman, 236–257. Oxford: Woodhead. Ashkenazi D, Nusbaum I, Shacham-Diamand Y, Cvikel D, Kahanov Y, Inberg A. A method of conserving ancient iron artefacts retrieved from shipwrecks using a combination of silane self-assembled monolayers and wax coating. Corros Sci. 2017;123:88–102. Barker D. 2006. Metals. In Conservation Science , by Eric May and Mark Jones, 131–136. Cambridge: The Royal Society of Chemistry. Favre-Quattropani L, Groening P, Ramseyer D, Schlapbach L. 2000. The protection of metallic archaeological objects using plasma polymer coatings. Surf Coat Technol 377–82. Hamilton DL, Dewolf H, Fix PD. 2017. Conservation. In La Belle: The Archaeology of a Seventeenth-Century Ship of New World Colonization , by Borgens, Jones, and Ray Bruseth, 62–64. College Station: Texas A&M University Press. Hamilton D. Methods for Conserving Material from Underwater Sites. College Station, TX: Texas A&M University; 1998. Kusmierek E, Chrzescijanska E. Tannic acid as corrosion inhibitor for metals and alloys. Mater Corros. 2015;66:169–74. Logan J, Selwyn L. 2007. Care and Cleaning of Iron. Canadian Conservation Institute Notes 9/6, Minister of Public Works and Government Services Canada. North NA. 1987. Conservation of Metals. In Conservation of Marine Archaeological Objects , by Colin Pearson, 207–232. Sydney: Butterworths. North NA, MacLeod I. 1987. Corrosion of Metals. In Conservation of Marine Archaeological Objects , by Colin Pearson, 76–80. Sydney: Butterworths. Pelikan JB. Conservation of Iron with Tannin. Stud Conserv. 1966;11(3):109–15. Sease C. Codes of Ethics for Conservation. Int J Cult Property. 1998;7(1):98–115. Sonneborn. n.d. Product Page for Multiwax 180-W. Sonneborn. Accessed April 10, 2024. https://www.sonneborn.com/en-us/product-finder?region=All%20regions&product=All%20product%20types&product=All%20product%20brands&product=All%20agriculture%20types&product=All%20animal%20health%20types&product=All%20candle%20types&product=All%20clean%20bea . General Services Administration US. 2017. Applying a Sacrificial Coating to Wrought Iron, Cast Iron and Steel. 12 22. Accessed 04 10, 2024. https://www.gsa.gov/real-estate/historic-preservation/historic-preservation-policy-tools/preservation-tools-resources/technical-procedures/applying-a-sacrificial-coating-to-wrought-iron-cast-iron-and-steel . Viduka A. 2012. Conservation and Finds Handling. In Training Manual for UNESCO Foundation Course on the Protection and Managment of Underwater Cultural Heritage in Asia and the Pacific , by M Manders and C. Underwood, 2–26. Bangkok: UNESCO. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-4468228","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":309610787,"identity":"6d47ecff-d791-4290-89f0-98b8c9f65c4e","order_by":0,"name":"Christopher Dostal","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAuElEQVRIiWNgGAWjYDCCAyCigEEOymUmSgtjA4MBgzEPyVoSe4jWwne8/fmDHwZ26fvZT6dJMFRYJzYQ0iJ55oxhY49Bcm4PT+42CYYz6YS1GNzIYWzgMTiQ28MA1MLYdpgYLekPG/8YHEjn4X8L1PKPKC0Jhs1AWxJ4JEC2NBChBeSX2TIGyYY9N95utkg4lm5MUAswxB58fFNhJ8/en7vxxocaa1mCWlBBAmnKR8EoGAWjYBTgAgDEikCvS+13QgAAAABJRU5ErkJggg==","orcid":"","institution":"Texas A\u0026M University","correspondingAuthor":true,"prefix":"","firstName":"Christopher","middleName":"","lastName":"Dostal","suffix":""}],"badges":[],"createdAt":"2024-05-23 16:38:09","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4468228/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4468228/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":58089575,"identity":"f6ac3e6b-d064-42fe-9e9d-53ca9a9155fa","added_by":"auto","created_at":"2024-06-11 03:55:40","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":6370680,"visible":true,"origin":"","legend":"\u003cp\u003eBefore conservation (top) and after (bottom) of a concreted cannon from the Savannah River in Georgia.\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-4468228/v1/32bb92d34e3e72fdc029bb4f.png"},{"id":58089572,"identity":"2b26e53a-4b22-4b9a-8694-d8ac9d767023","added_by":"auto","created_at":"2024-06-11 03:55:40","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":312977,"visible":true,"origin":"","legend":"\u003cp\u003eApplying tannic acid to a cannon fresh from the boiling DI water rinses.\u003c/p\u003e","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4468228/v1/686e658a9bfc251fbe70bed6.jpg"},{"id":58089573,"identity":"fefb4920-279a-42ed-91d4-f6b2d51f078a","added_by":"auto","created_at":"2024-06-11 03:55:40","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":64374,"visible":true,"origin":"","legend":"\u003cp\u003ePost tannic acid, a cannon being lowered into molten microcrystalline wax.\u003c/p\u003e","description":"","filename":"Figure3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4468228/v1/f15f1310f68e118639512d35.jpg"},{"id":58089577,"identity":"8b7decfe-e6c9-4f28-b2b2-292e69870edc","added_by":"auto","created_at":"2024-06-11 03:55:40","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":11137012,"visible":true,"origin":"","legend":"\u003cp\u003ePre- and Post- Conservation photos of one of the cannon conserved for the State of Louisiana.\u003c/p\u003e","description":"","filename":"Figure4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4468228/v1/fe46faefb926ff9b7c0bfc4e.jpg"},{"id":58089576,"identity":"e269e149-774b-434e-bb85-baa62e324c99","added_by":"auto","created_at":"2024-06-11 03:55:40","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":387251,"visible":true,"origin":"","legend":"\u003cp\u003eThe Blomefield Cannon with wax, then paint, after over a year on display outdoors near the Gulf of Mexico at the Maritime Museum Louisiana. Photo courtesy of Chloe Stephan, Maritime Museum Louisiana.\u003c/p\u003e","description":"","filename":"figure5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4468228/v1/683bc0faff207c8b73fe6ee8.jpg"},{"id":58089574,"identity":"6fbe5a5d-7c7e-4724-aad3-6ecd69bb0949","added_by":"auto","created_at":"2024-06-11 03:55:40","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":299348,"visible":true,"origin":"","legend":"\u003cp\u003eWear indicated by spots of glossy paint, likely due to straddling or sitting on the cannon. Photo courtesy of Chloe Stephan, Maritime Museum Louisiana\u003c/p\u003e","description":"","filename":"Figure6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4468228/v1/a586a4e04d3bde3f8b8552d9.jpg"},{"id":67700236,"identity":"3318c2e7-4952-46b1-aa71-319fb3fe6804","added_by":"auto","created_at":"2024-10-28 21:31:39","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":18304819,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4468228/v1/374fd7dc-8b96-4547-892e-01ecd26e71ad.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Improving the Final Atmospheric Seal of Conserved Archaeological Iron from Marine Sites","fulltext":[{"header":"Introduction","content":"\u003cp\u003eMaritime archaeologists have long been forced to grapple with the cruel reality of electrochemical corrosion of iron artifacts from shipwrecks and other submerged sites. Iron is the constituent component of a host of materials found on ships, from cannons to anchors to the ships stove, to rigging elements to ammunition. The post-depositional environment of any marine archaeological site is dynamic and varied, but the one inevitably reliable through line is the encrustation and corrosion of iron materials. The journey from the encrusted conglomerate that arrives at the lab to the clean, conserved material that leaves is incredibly satisfying to behold, but the processes of corrosion do not end when the objects leave the lab, and as such a re-evaluation of the final sealant that impacts the rate of future corrosion is warranted (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe mechanism for corrosion of wrought and cast-iron archaeological materials in marine environments sites is well-understood [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Additionally, though there are varying degrees of consensus, there are several widely accepted conservation processes to stabilize archaeological iron, including chemical reduction, electrolytic reduction, and chemical cleaning [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. A significant amount of scholarship has been dedicated to these two aspects of iron conservation, but there has been little done on the assessment of the final step of the conservation treatment, the sealant applied to the object to inhibit future corrosion. This paper addresses a series of recent experiments undertaken to improve the final atmospheric seal of conserved iron.\u003c/p\u003e \u003cp\u003eAt the Conservation Research Laboratory (CRL) at Texas A\u0026amp;M University, per the guidelines established by Hamilton [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], the vast majority of iron archaeological materials from marine sites are treated via electrolysis after mechanical deconcretion. Electrolysis is typically undertaken with three stages of current density:\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003e0.001\u0026ndash;0.005 amp/cm\u003csup\u003e2\u003c/sup\u003e to reduce ferrous corrosion compounds (Fe\u003csup\u003e2+\u003c/sup\u003e) to a more stable, metallic-like state of magnetite (Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e)\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003e0.05 amp/cm\u003csup\u003e2\u003c/sup\u003e for chloride removal\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003e0.1 amp/cm\u003csup\u003e2\u003c/sup\u003e for mechanical cleaning via the evolution of hydrogen on the surface of the metal [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Note that the higher current density is only carried out if the underlying metal is sturdy enough to withstand the enhanced hydrogen evolution.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e \u003cp\u003eOnce reduction is complete and the chloride concentration is stable and low in the solution (\u0026lt;\u0026thinsp;10ppm as analyzed via mercuric nitrate (Hg(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e) titration), the objects are removed from the electrolysis vat and placed in a series of boiling deionized water baths to remove residual electrolyte until the pH stabilizes. At this stage, historical cast or wrought iron is composed of a composite mix of graphite, metallic iron, and reduced iron corrosion in the form of magnetite. With the hot water from the rinse promoting electron exchange from the anodic graphite to the cathodic metallic iron, the surface of the object will begin corroding again immediately upon removal from the water [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTo limit this post-boil corrosion, the galvanic cell must be interrupted by either removing the oxygen or the electrolyte, in this case, water. Removing the oxygen from the room tends to be detrimental to the productivity of the conservators, so instead either the water must be removed or a surface coating applied to block the oxygen. North [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] recommends solvent dehydration via acetone submersion for cast iron objects, though in practice, this is not practical for substantial artifact assemblages or for very large objects like cannon or anchors. In lieu of this, the CRL utilizes dewatering via submersion in molten microcrystalline wax, as outlined below. As soon as an object is removed from the boil, three coats of 20% technical grade tannic acid in deionized water and ethanol are applied via brushing (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e2\u003c/span\u003e). (For large cannons, we use tennis balls screwed to a long piece of bamboo to paint the bore). The tannic acid forms a corrosion inhibiting barrier of ferric tannate (Fe\u003csub\u003e2\u003c/sub\u003e(C\u003csub\u003e14\u003c/sub\u003eH\u003csub\u003e7\u003c/sub\u003eO\u003csub\u003e9\u003c/sub\u003e)(OH)\u003csub\u003e3\u003c/sub\u003e) on the surface [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. There are several commercial corrosion resistant coatings available, and through experiments we have found them to be equally effective, but not as aesthetically pleasing.\u003c/p\u003e \u003cp\u003eOnce the tannic acid coats are dry, the final stage is the atmospheric sealant. For this, there are two broad options: either some kind of wax barrier, or a paint covering. In practice, the application of microcrystalline wax has proven to be the most effective option for long term preservation, which is likely linked to the typical method of application. Unlike painting, which is a surface application, wax is applied by submersing the artifacts in 175\u0026deg;C wax until all residual moisture is driven from the object. Then the wax is cooled to ~\u0026thinsp;100\u0026deg;C and the artifact is removed (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Crucially, driving the moisture out and replacing it with wax significantly limits potential electrolyte for future corrosion. Objects that are either too large to immerse in wax or objects that will be stored outdoors or in areas where they will be in contact with the public are generally sealed with paint, as it provides a more durable barrier from physical contact and is more resistant to the elements. Even so, painted objects tend to produce more visible corrosion more quickly after conservation due to the aforementioned residual moisture.\u003c/p\u003e \u003cp\u003eApart from the differences in efficacy, the reversibility of each sealant is a factor. Reversability is a cornerstone of archaeological conservation ethics, and unless absolutely necessary, all methodologies and chemicals used should be reversible [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] Microcrystalline wax of similar formulations to the one used by CRL conservators is easily one of the most reversable sealants, because with a melting point of 86.4\u0026deg;C, it can removed by simply submerging the object in boiling water, or removed with a heat gun [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Certain paints are easier to remove than others, though most tend to be emulsions which once dry, require a mixture of solvents to remove. Some paints are not readily soluble in solvents at all, though most can be removed with either a poultice of sodium hydroxide (NaOH) or mechanically by scraping or with a pressure washer if the underlying metal is sturdy enough.\u003c/p\u003e \u003cp\u003ePreviously, publications and conversations about final sealants have been centered on using wax, paint, or some other sealant, often experimental in nature. Generally, the consensus reflects what is stated above, that wax coatings are preferred, but not suitable for outdoor display [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. It has also been long held anecdotally that you cannot paint over an object treated with wax, because at warmer temperatures the wax will melt, loosening the paint. Through a happy accident, the CRL has discovered that not only is this not true, but when possible, combining microcrystalline wax and paint provides the benefits of both treatments with no discernable drawbacks.\u003c/p\u003e"},{"header":"Methods/Experimental","content":"\u003cp\u003eIn June of 2021, the Louisiana Department of Culture, Recreation and Tourism, Office of Cultural Development, Division of Archaeology contracted with the CRL to conserve two cast iron cannons recovered in New Orleans. One of the cannons was an 18-pdr carronade, the other was labelled as a 6-pdr, but subsequent analysis revealed it to be a Blomefield pattern 9pdr. Per the original agreement, the cannons were to be sealed with microcrystalline wax, with the explicit wording from the CRL contract stating that \u0026ldquo;this finish coating is suitable for indoor museum displays, but will not survive the outside elements\u0026rdquo;. Both cannons were mechanically cleaned and then put through the electrolytic reduction process from June of 2021 to January of 2022. In January and February, the cannons underwent extensive boiling rinses in deionized water and were given three coats of tannic acid, then sealed with microcrystalline wax via submersion.\u003c/p\u003e \u003cp\u003eIn May of 2022, after the removal from wax, the Louisiana State Archaeologist indicated to the CRL that there had been a change of plans, and that the Blomefield 9pdr was going to be displayed outside of the Maritime Museum Louisiana in Madisonville, LA. Concerned that in the summer heat of Louisiana the wax would become tacky and wear off, we decided that the cannon would need to be painted.\u003c/p\u003e \u003cp\u003eInstead of proceeding with the removal of the wax by re-boiling the cannon, we requested to conduct an experiment to determine if the wax actually needed to be removed. We took a rusty cast iron floor drain grate, ran it through ER, coated it in tannic acid, submerged it in molten microcrystalline wax, and then painted it with the standard paint the CRL uses for outdoor artillery and anchor displays.\u003csup\u003e1\u003c/sup\u003e Then the grate was placed outside and allowed to sit from May to June, where it was exposed to sustained high temperatures of 100\u0026ndash;102\u0026deg;F. Even on the hottest days, there was no loosening of the adhesion, and the grate remained in superb condition.\u003c/p\u003e \u003cp\u003eGiven the results, we were given the go ahead to paint over the wax for both of the cannon in June of 2022. After returning both cannon to Louisiana, one of the cannon was placed in a curatorial space, and the other outside of the Maritime Museum Louisiana in Madisonville on March 22, 2023. Following the suggestions of the maintenance team from the National Parks Service Castillo de San Marcos in St. Augustine, Florida, we applied an undercoat of cherry-red paint followed by two coats of black paint. The black paint is generally accepted as the best way to present the color of cast and wrought iron, and the undercoat of cherry-red serves as a warning that the topcoats are getting worn or chipped.\u003c/p\u003e\n\u003col\u003e\u003cli\u003e\u003cspan\u003e Benjamin Moore Super Spec\u0026trade; HP D.T.M Alkyd Low Lustre paint, Black P23 80.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Results and Discussion","content":"\u003cp\u003eThe drain grate continues its exposure to the elements as of this publication date. The summers of 2022 and 2023 in Bryan, Texas were exceptionally hot and dry, exposing the grate to extended periods of significant heat above 100\u0026deg;F, as well as multiple periods of hard-freeze weather (\u0026lt;\u0026thinsp;20\u0026deg;F), driving rains, hail, significant wind, etc. As of this writing, visual and physical inspection reveals no significant wear and no corrosion (the color of the paint has faded slightly).\u003c/p\u003e \u003cp\u003eAssessment of the cannon has proven similarly positive results there. One year later, the Blomefield cannon outside of the Maritime Museum has no indication of corrosion, though there does appear to be some wear on the outermost layer of paint. Given that the cannon is positioned in an area that is accessible to the public, this is accepted as normal wear and tear as the cannon is touched.\u003c/p\u003e \u003cp\u003eGiven the positive results of the experiment and the resulting cannon treatments, the recommendation of the author is to combine microcrystalline wax with a suitable outdoor paint for the best results when conserving iron that will be displayed outdoors or will be potentially accessible by members of the public. The removal of residual moisture in the iron and replacing empty spaces in porous iron leads to longer lasting corrosion resistance, while the addition of the paint protects the wax and provides a stronger barrier against abrasions and wear that are inevitable for objects subjected to the elements or by over eager members of the public.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThis study has demonstrated the efficacy of combining microcrystalline wax with paint as a conservation treatment for iron artifacts intended for outdoor display or interaction with the public. The experimental results from the application on both a test iron grate and two historic cannons have shown that this method offers superior preservation qualities under various environmental conditions, including extreme temperatures, precipitation, and mechanical wear.\u003c/p\u003e \u003cp\u003eThe success of this treatment is primarily attributed to the synergistic effect of microcrystalline wax and paint. The microcrystalline wax acts as a critical barrier to moisture, effectively limiting the electrolyte's presence necessary for corrosion processes. The subsequent application of paint not only enhances the aesthetic presentation of the artifacts but also provides an additional durable layer against physical damage and environmental exposure. This dual-layer approach not only preserves the integrity of the iron artifacts but also facilitates their maintenance, as indicated by the cherry-red undercoat's practical utility in monitoring wear and tear.\u003c/p\u003e \u003cp\u003eWhile the findings of this study are promising, further research is necessary to determine the longevity of this treatment method as opposed to just wax or just paint. Because of the promising results from the Blomefield cannon, a second cache of cannon from the Savannah River are being treated with the same wax/paint combination. A follow-up study will be conducted in the coming years on both cannon groups to determine long term durability.\u003c/p\u003e \u003cp\u003eThe integration of microcrystalline wax and paint represents a significant advancement in the conservation of iron artifacts, particularly those exposed to outdoor environments or direct public interaction. This study's findings suggest that conservation practitioners should consider this method for its efficacy, practicality, and aesthetic benefits. Additionally, the reversibility of the treatment ensures that future conservation efforts can adapt to new technologies and methodologies without compromising the artifact's historical value.\u003c/p\u003e \u003cp\u003eThis research contributes to the broader field of archaeological conservation by offering a novel approach to preserving iron artifacts. It underscores the importance of interdisciplinary collaboration in developing conservation strategies that are both effective and respectful of historical integrity. As we move forward, it is crucial that conservation practices continue to evolve, incorporating both traditional knowledge and innovative technologies to protect our cultural heritage for future generations.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eCRL\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eConservation Research Laboratory\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003eThis research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eAvailability of data and materials\u003c/em\u003e: Not Applicable\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eCompeting interests\u003c/em\u003e: The author declares that they have no competing interests\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eFunding\u003c/em\u003e: The conservation of the cannon came from the Louisiana Department of Culture, Recreation and Tourism, Office of Cultural Development, Division of Archaeology, and though that was the impetus for this project, they did not directly fund the experiment, analysis, or writing for this publication. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eAuthors\u0026apos; contributions\u003c/em\u003e: CD is the sole author.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eAcknowledgements\u003c/em\u003e: Special thanks to Dr. Chip McGimsey, State Archaeologist, LA division of Archaeology for allowing us to proceed with the experiment. This work was facilitated by the exceptional staff conservators at the CRL who helped with these experiments, especially John Hamilton. Finally, a hearty thank you to Chloe Stephan at the Maritime Museum Louisiana, whose photos were crucial to this paper.\u003c/p\u003e\n\u003cp\u003eAuthor Information: Chris Dostal is the director of the Conservation Research Laboratory and an assistant professor in the nautical archaeology program at Texas A\u0026amp;M University.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAngelini E, Grassini S, Tusa S. 2013. Underwater Corrosion of Metallic Heritage Artefacts. In \u003cem\u003eCorrosion and Conservation of Cultural Heritage Metallic ArteFacts\u003c/em\u003e, by Watkinson, Angelini, and Adriens Dillman, 236\u0026ndash;257. Oxford: Woodhead.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAshkenazi D, Nusbaum I, Shacham-Diamand Y, Cvikel D, Kahanov Y, Inberg A. A method of conserving ancient iron artefacts retrieved from shipwrecks using a combination of silane self-assembled monolayers and wax coating. Corros Sci. 2017;123:88\u0026ndash;102.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBarker D. 2006. Metals. In \u003cem\u003eConservation Science\u003c/em\u003e, by Eric May and Mark Jones, 131\u0026ndash;136. Cambridge: The Royal Society of Chemistry.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFavre-Quattropani L, Groening P, Ramseyer D, Schlapbach L. 2000. The protection of metallic archaeological objects using plasma polymer coatings. Surf Coat Technol 377\u0026ndash;82.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHamilton DL, Dewolf H, Fix PD. 2017. Conservation. In \u003cem\u003eLa Belle: The Archaeology of a Seventeenth-Century Ship of New World Colonization\u003c/em\u003e, by Borgens, Jones, and Ray Bruseth, 62\u0026ndash;64. College Station: Texas A\u0026amp;M University Press.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHamilton D. Methods for Conserving Material from Underwater Sites. College Station, TX: Texas A\u0026amp;M University; 1998.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKusmierek E, Chrzescijanska E. Tannic acid as corrosion inhibitor for metals and alloys. Mater Corros. 2015;66:169\u0026ndash;74.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLogan J, Selwyn L. 2007. \u003cem\u003eCare and Cleaning of Iron.\u003c/em\u003e Canadian Conservation Institute Notes 9/6, Minister of Public Works and Government Services Canada.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNorth NA. 1987. Conservation of Metals. In \u003cem\u003eConservation of Marine Archaeological Objects\u003c/em\u003e, by Colin Pearson, 207\u0026ndash;232. Sydney: Butterworths.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNorth NA, MacLeod I. 1987. Corrosion of Metals. In \u003cem\u003eConservation of Marine Archaeological Objects\u003c/em\u003e, by Colin Pearson, 76\u0026ndash;80. Sydney: Butterworths.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePelikan JB. Conservation of Iron with Tannin. Stud Conserv. 1966;11(3):109\u0026ndash;15.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSease C. Codes of Ethics for Conservation. Int J Cult Property. 1998;7(1):98\u0026ndash;115.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSonneborn. n.d. Product Page for Multiwax 180-W. \u003cem\u003eSonneborn.\u003c/em\u003e Accessed April 10, 2024. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.sonneborn.com/en-us/product-finder?region=All%20regions\u0026amp;product=All%20product%20types\u0026amp;product=All%20product%20brands\u0026amp;product=All%20agriculture%20types\u0026amp;product=All%20animal%20health%20types\u0026amp;product=All%20candle%20types\u0026amp;product=All%20clean%20bea\u003c/span\u003e\u003cspan address=\"https://www.sonneborn.com/en-us/product-finder?region=All%20regions\u0026amp;product=All%20product%20types\u0026amp;product=All%20product%20brands\u0026amp;product=All%20agriculture%20types\u0026amp;product=All%20animal%20health%20types\u0026amp;product=All%20candle%20types\u0026amp;product=All%20clean%20bea\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGeneral Services Administration US. 2017. \u003cem\u003eApplying a Sacrificial Coating to Wrought Iron, Cast Iron and Steel.\u003c/em\u003e 12 22. Accessed 04 10, 2024. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.gsa.gov/real-estate/historic-preservation/historic-preservation-policy-tools/preservation-tools-resources/technical-procedures/applying-a-sacrificial-coating-to-wrought-iron-cast-iron-and-steel\u003c/span\u003e\u003cspan address=\"https://www.gsa.gov/real-estate/historic-preservation/historic-preservation-policy-tools/preservation-tools-resources/technical-procedures/applying-a-sacrificial-coating-to-wrought-iron-cast-iron-and-steel\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eViduka A. 2012. Conservation and Finds Handling. In \u003cem\u003eTraining Manual for UNESCO Foundation Course on the Protection and Managment of Underwater Cultural Heritage in Asia and the Pacific\u003c/em\u003e, by M Manders and C. Underwood, 2\u0026ndash;26. Bangkok: UNESCO.\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":"Conservation, Electrolysis, Surface Coatings, Curation, Marine Sites, Iron","lastPublishedDoi":"10.21203/rs.3.rs-4468228/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4468228/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe conservation of iron artifacts from marine archaeological sites faces the persistent challenge of electrochemical corrosion post-recovery. Traditional conservation methods, such as electrolytic reduction and chemical stabilization, have been very successful in stabilizing these artifacts, but post-treatment, can do little to provide durable long-term protection when exposed to atmospheric conditions. This study investigates the efficacy of a novel conservation treatment that combines microcrystalline wax with a paint overlay, aimed at improving the final atmospheric seal of conserved iron artifacts. Conducted at the Conservation Research Laboratory (CRL) at Texas A\u0026amp;M University, the experiment involved treating two historically significant cannons with this dual-layer method. The cannons were subjected to rigorous environmental conditions to test the durability and protective quality of the treatment. Results indicate that the combined use of microcrystalline wax and paint not only enhances the corrosion resistance of iron artifacts but also maintains aesthetic and structural integrity under variable climatic exposures. This paper discusses the experimental procedures, findings, and the practical implications of this treatment, advocating for its application in both museum settings and outdoor displays. The study contributes a significant advancement to conservation practices, offering a reversible, effective solution that upholds the artifact's historical value while extending its lifespan.\u003c/p\u003e","manuscriptTitle":"Improving the Final Atmospheric Seal of Conserved Archaeological Iron from Marine Sites","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-11 03:55:36","doi":"10.21203/rs.3.rs-4468228/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":"7309c30a-51f6-4f17-8e63-5b4d50d445e8","owner":[],"postedDate":"June 11th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-10-28T21:23:26+00:00","versionOfRecord":[],"versionCreatedAt":"2024-06-11 03:55:36","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4468228","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4468228","identity":"rs-4468228","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}