Corrosion Failure Mechanism of Sprayed Zinc-Aluminum (ZAA) Coatings in Simulated Marine Environment

Several zinc-aluminum coatings were prepared, parts of them were sealed with organic coating, and then their corrosion behavior and mechanism were studied by salt spray test and electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to assess the coatings. The results showed that the zinc-aluminum coatings were rough and with some defects, which would weaken the protection effect. The organic coating would improve the protection through sealing the defects of the metal coating. The zinc-aluminum coating would maximize the protection of the base, because the aluminum would seal not only the zinc layer, but also the defects of the zinc layer.