Improvement of stainless steels adhesive bonding using anodizing treatments

We have studied the influence of anodic oxidation in sulfuric and nitric environment on bonding an epoxy resin with an AISI 304 (XSCrNi18-10) stainless steel, It is shown that the grain boundaries are attacked during the anodic oxidation treatment and that the thickness of the secondary passivity film increases in correlation to an enrichment in Cr and a hydration of the surface. A good correlation is obtained between the physico-chemical parameters of the surfaces and the durability of assemblies, Thus, in order to obtain the best results, a microroughness (engraving the grain boundaries) must be combined with a high surface chromium content.