Mechanism of Stress-Corrosion Cracking of Mild Steel in Nitrate Solution

Abstract

Various models for the stress-corrosion cracking (SCC) process in mild steel are reviewed. They can essentially be classified into two main groups: hydrogen-induced SCC and dissolution at the stresscorrosion (SC) crack tip. The first group is excluded on the basis of the present experimental results for SCC of mild steels in nitrate solutions which are consistent with a slip-dissolution process. Susceptibility to intergranular corrosion (IGC) is not a necessary condition for the occurrence of intergranular SCC. Decarburised specimens showed a higher resistance to SCC than decarburised and then nitrided specimens. The experimental results suggest that an excess of nitrogen dissolved at grain boundaries has less influence on susceptibility to intergranular SCC than fine carbide precipitates or an excess of carbon dissolved at grain boundaries.