Effects of Temperature and Chloride Concentration on Pit Initiation and Early Pit Growth of Stainless Steel

Abstract

The influences of temperature and chloride concentration on pitting corrosion of stainless steel AISI 304 were investigated. Conventional large-scale measurements (sample diameter, were conducted to study the effect of temperature on pit initiation, metastable and stable pitting in 0.1 M and in 0.1 M NaCl solutions at 0, 30, 60, and 90°C. Microelectrochemical measurements μm) were performed to investigate pit initiation events at room temperature, 60, and 90°C in in NaCl, and in LiCl solutions of various concentrations (0.01-10 M It was found that the MnS inclusions dissolved at lower potentials when the temperature was increased. In the presence of chlorides, an increase in temperature influenced pit growth and decreased the pitting potential. The temperature was found to aid in stabilizing pit growth and hindering repassivation. Pitting corrosion at single MnS inclusions was initiated by conducting potential sweeps with a microelectrochemical cell until the pitting potential was reached. In the presence of chlorides, pits initiated at the interface of the MnS inclusions and the metal matrix. The extent and morphology of the attack at the interface between the inclusion and the metal matrix varied with chloride concentration and temperature. At high temperatures and high chloride concentrations, numerous additional initiation processes on the passive surface around the larger inclusions are taking place, leading to an etching-type corrosion of this area. © 2001 The Electrochemical Society. All rights reserved.