Corrosion behavior in seawater of arc thermal sprayed Inconel 625 coatings with sealing treatment

In this study, zinc powder (Zinc), inorganic ceramic (Ceramic), and organic-inorganic composite ceramic (Hybrid) sealing processes were applied to improve the corrosion resistance of arc thermal sprayed Inconel 625 coatings. The Inconel 625 coating in seawater solution showed poor corrosion resistance due to its porosity and Cr depletion resulting from Cr oxide formation during the arc thermal spraying process. Zinc sealing formed a stable cathodic protection, but the local corrosion damage occurred largely in the anodic polarization experiment caused by an excessive dissolution reaction and a weak bonding force between the zinc particles. Hybrid sealing gave a better sealing effect, but surface corrosion damage appeared due to interconnected micro-crack defects on the surface. Ceramic sealing gave the best corrosion protection due to a high sealing efficiency and a lower surface damage tendency resulting from effectively blocked defects of the Inconel 625 coating.