Improving the long-term corrosion resistance of HVOF sprayed WC-Cr3C2-Ni coating by vacuum sealing with silicone resin

Abstract

The properties of thermal sprayed WC based cermet coatings are limited by their structural defects, especially corrosion resistance. This article studied the influence of vacuum sealing with silicone resin on the long-term corrosion resistance of HVOF sprayed WC-Cr3C2-Ni coating in 3.5 wt.% NaCl solution. The surface morphologies of the unsealed and sealed coatings show the high compatibility between sealant and WC-Cr3C2-Ni coating. Benefiting from the block of sealant in defects, the sealed coating presents lower corrosion current density (5.843 × 10−8 A cm−2) after long-term corrosion than the unsealed coating (1.776 × 10−7 A cm−2). Owing to the vacuum treatment, sealant adequately penetrates and remains inside the WC-Cr3C2-Ni coating, and inhibits the growth of corrosion pits on the sealed coating surface. The vacuum sealing with silicone resin effectively hinders the diffusion of corrosion solution, and provides practicable strategy to improve the corrosion resistance of the coatings.

Keywords

• WC-Cr3C2-Ni coating
• HVOF
• Long-term corrosion
• Vacuum sealing
• Silicone resin