Robust the corrosion-blocking behavior, mechanical and UV aging resistance properties of epoxy composite coating encapsulated with mixed metal complexes for steel surface applications

Enhancing the protective demeanor, mechanical toughness and UV immovability of epoxy coating using metal-organic complexes as network crosslinking accelerators is on top of interest by coating formulators. The present work investigates the incorporation of mixed ligand Zr(IV) and Cu(II) complexes of metformin (MF) and 2.2′bipyridine (Bipy) against the free ligands as cross-linking modifiers via epoxy coating surface to construct high build cured epoxy adduct. Based on the calculated energy values, Zr(IV) and Cu(II) demonstrated the least energy gap (∆E) values at 0.190 au compared to free MF and Bipy lignads. Furthermore, measured electronic transition configurations illustrated that Cu(II) had four electronic transitions (n-π * , π-π * , d-d and LMCT). Some modified epoxy coating formulations with the same loading level (%) of MF, Bipy, Zr(IV) and Cu(II) compounds were prepared and assessed. EIS measurements using high saline formation water as corrosive medium were performed and offered that PA-DGEBA/MC-Cu coated film showed the superior resistance values (R ct = 940 and R p = 930 kΩ cm 2 ) and attained the best protection efficiency (PE) at 97.07%. Salt spray corrosion experiment clarified that PA-DGEBA/MC-Cu coating fulfilled the least corrosion rate (CR) at 0.00049 mm/y and exhibited the highest PE of 99.84%. SEM/EDX combination survey affirmed the protective performance of the checked coatings. AFM microanalysis affirmed that surface treated Cu(II) coating displayed the smoothest coating surface with robust layer curing. Mechanical durability properties were evaluated and illustrated that pull-off adhesion for PA-DGEBA/MC-Cu coated film fulfilled the best adherent layer at 6.3 MPa. Furthermore, bend character was estimated to achieve the best elongation for modified Cu(II) coating at 77, and presented the highest resistance to rapid deformation (impact) at 59.7 J. UV immovability trial affirmed that PA-DGEBA/MC-Cu coated film presented the highest resistance to UV irradiance with blistering (#8 size and few frequency) with offering the least gloss variation and matt properties. The elevated resistance properties illustrated by surface modified Cu(II) complex coating could be attributed to Cu(II) magnetic property, enhanced electronegativity, lower energy gap and offering four electronic transitions in which boosted the interface interactions and cross-linking intensity, thereby consolidating the epoxy/steel interfacial adhesion and boosting film stiffness.