Effect of grit blasting of substrate on the corrosion behaviour of plasma-sprayed Al2O3 coatings

In this study, the corrosion behaviour of grit-blasted AISI 304L stainless steel substrates coated with Al2O3 was investigated in 1 N H2SO4 solution. Coatings were produced by employing a plasma-spray process. The phase analysis of powders and coatings was evaluated by means of optical microscopy and X-ray diffractometry. The microstructure of the coating was characterised with optical microscopy. The corrosion rates of these coatings were measured according to ASTM G 31-72 standard. The results indicated that the adherence of Al2O3 coatings on the substrate, the surface roughness and the corrosion rate depend on the parameters of grit blasting. It is also found that the corrosion resistance of plasma-sprayed coatings was reduced with increasing surface roughness and increased considerably with decreasing porosity and coating thickness. (C) 1999 Elsevier Science S.A. All rights reserved.