Mechanical and electrochemical interactions during liquid-solid impingement on high-alloy stainless steels

The erosion-corrosion behaviour of three hi.-h-alloy stainless steels (UNS S31245, UNS S32654 and UNS S32750) under aggressive liquid-solid impingemen t conditions has been assessed using a combination of electrochemical tests and weight-loss analysis. The material loss occurring under conditions of varying solid loading (900 mg/l), and at a temperature of 18 degreesC, velo city of 17 m/s and impingement,A angle of 90 degrees has been scrutinised a s a function of time. Post-test examination has identified material loss me chanisms and the physical relevance of erosion and corrosion interactions h as been illustrated. In this paper it has been shown that the resistance to material loss for th e three materials does not follow the expected trend of increasing resistan ce as hardness increases. Through electrochemical measurements the pure cor rosion component of the material can be isolated and it has become clear th at corrosion (through direct and indirect effects) plays an important role in the erosion-corrosion process of even high-grade stainless steels due to depassivation-repassivation events corresponding to solid impact in the co rrosive medium. Although the pure corrosion process (direct corrosion effec t) constitutes only a small part of the total material loss, there is an im portant synergistic factor defined as the effect of corrosion on erosion wh ich means that corrosion-related processes can be significant in erosion-co rrosion. (C) 2001 Elsevier Science B.V. All rights reserved.