Corrosion of plasma sprayed NiCrAl/Al 2 O 3 –13 wt-%TiO 2 coatings with and without sealing

Abstract

Plasma spraying is a well established technique for many industrial applications. In the present study, plasma sprayed Al₂O₃+13 wt-%TiO₂ coatings with bond layer of NiCrAl were prepared and characterised by optical microscopy, scanning electron microscopy and X-ray diffraction. Silicone resin sealing treatment was applied to the coating, and the salt spray test and electrochemical testing were conducted to investigate the effect of the sealant on the corrosion resistance of the coatings. It was found that the sealants filled the pores and microcracks in the coating and formed a thin layer with the ceramic, protecting the substrate from corrosion, while the as sprayed coating was subjected to pitting corrosion in the form of electrochemical corrosion at the interface between the bonding layer and the substrate.