Effects of sealing on corrosion behaviour of plasma-sprayed Cr₂O₃–8TiO₂ coating

Abstract

Plasma-sprayed Cr₂O₃–8 wt-% TiO₂ coatings were deposited on mild steel and sealed by epoxy resin and silicone resin in different processes. The microstructure and corrosion resistance of all coatings were investigated. The results showed that silicone resin sealant can seal the coating well and 91% of interconnected porosity was blocked. The sealant can penetrate into the coating by more than 280 μm. The coating sealed with silicone resin in vacuum conditions had the highest corrosion potential E_corr (−375 mV) and lowest corrosion current density i_corr (17 mA m⁻²) in electrochemical tests. Correspondingly, the unsealed coating had the lowest E_corr and highest i_corr. The corrosion resistance of the coatings was in the following order: coating sealed with silicone resin in vacuum>coating sealed with silicone resin in air>coating sealed with epoxy resin in vacuum>coating sealed with epoxy resin in air>unsealed coating.

Keywords:

• Coating
• Plasma-sprayed
• Sealing
• Corrosion

The work was financed by the Ministry of Education, Jiangsu Province of China, under project JHZD09-04. It was also supported by the National Natural Science Foundation of China (no. 51105129). The authors wish to thank Mrs Yu Yi and Master Jia Shao for assistance in experimental work.