Influence of the exposure of AISI 304L stainless steel at moderately high temperature on the susceptibility to crevice corrosion

Abstract

Stainless steels passivate in air by forming a very thin (a few nanometre thick) protective film of Fe and Cr mixed oxides. The nature and the protective properties of this film change if the stainless steel surface is previously exposed to elevated temperatures. Thermal treatment, chemical processes and mechanical manufacture to which stainless steel surfaces are normally subject, result in changes to the surface conditions, and therefore to modification of the corrosion resistance. Among the various forms of corrosion of stainless steels, crevice corrosion is undoubtedly the most common in industrial environments and one of the most insidious from an engineering point of view. In this work the effects of surface conditions, in particular as a consequence of exposure at moderately high temperature ranging between 150 and 300°C, on the corrosion behaviour of type AISI 304L stainless steel have been investigated. The aim has been to verify if common treatments causing local heating, such as welding, even in remote regions, thermal stretching, grinding, exposure to superheated steam, or sterilisation processes can constitute aggravating circumstances in respect of crevice corrosion susceptibility.