Corrosion Performance of Acrylic–Polyurethane and Polyacrylamide Coatings on Quaternary Bronze

ABSTRACT To mitigate outdoor corrosion of cultural bronze, this study compares three transparent polymer coatings—PUR‐129 (acrylic–polyurethane), Paraloid B‐82 (acrylic), and polyacrylamide (PACM)—applied as monolayer, multilayer, and emulsion films on quaternary bronze coupons replicating the alloy of Sabil al‐Ahmadi's window grilles (Tanta, Egypt). Performance was assessed after 12 months of on‐site natural exposure using weight change, gloss retention, and electrochemical testing (OCP, EIS, and potentiodynamic polarization). Post‐aging SEM/EDS characterized surface morphology, coating thickness, and elemental signatures. Across metrics, multilayer designs outperformed single‐layer applications; PUR‐129 multilayer was consistently the top performer, maintaining ~90.5% gloss, showing the lowest weight change, and exhibiting the highest electrochemical barrier relative to the bare control. The results indicate that transparent multilayer polymer systems—particularly PUR‐129—provide durable protection for outdoor bronze while better preserving visual appearance under the Nile Delta climate.