The effect of low pH in erosion-corrosion resistance of high chromium cast irons and stainless steels

Abstract

Corrosive wear is a form of material degradation that is known to occur on equipment and components that handle suspended solids in aqueous solutions. This surface deterioration process is generally enhanced when the fluids contain chlorides that are acidic in nature. Such environments are encountered in many applications, one such example being the minerals processing industry.High chromium white cast irons are widely used in many engineering applications as they extend the service life beyond that of stainless steels. In this work, the corrosive wear of austenitic stainless steel UNS S31600 and martensitic stainless steel UNS S42000 are compared with high chromium white cast irons (27WCI and 37WCI) by using a submerged jet technique at perpendicular incidence. The testing medium consisted of 3.5% NaCl liquid solution (pH 7 and pH 3) with suspended silica sand particles. The post-test methodology characterised the material loss within the directly impinged zone and turbulent zone where abrasive damage is involved. In neutral conditions, the presence of chromium carbides in white cast irons provided benefits, whilst in the acidic conditions, the austenitic structured materials (for stainless steels and white cast irons) suffered lower overall material loss compared with the martensitic structured materials.