Effect of Defect Size on Corrosion Behaviors of Arc Sprayed Al–Zn–Si–RE Alloy Coatings in 5% NaCl Solutions

Abstract To investigate the cathodic protection performance of arc‐sprayed Al–Zn–Si–RE (Rare Earth Element) alloy coatings, electrochemical corrosion behaviors of coatings with artificial scratches of different sizes were studied via electrochemical impedance spectroscopy (EIS) and open‐circuit potential‐time ( E corr ‐ t ) curves. The effect of defect size on the corrosion behaviors of 55% Al–Zn‐1.6% Si alloy coating in 5 wt% NaCl solution was analyzed. Results show that the corrosion process of intact coating includes five stages: pitting of oxide film on coating surface, active dissolution of coating, cathodic protection provided by coating, physical shielding of corrosion products, and coating failure. Wider scratch width leads to more significant impacts on corrosion behaviors and mechanisms of the coating, thereby influencing its service life. Al–Zn–Si–RE coatings exhibit excellent cathodic protection capability, and the protective lifespan of coatings with scratch width less than 3 mm exceeds 50 days.