Microstructure, heat treatment and pitting corrosion of 13CrNiMo plate and weld metals

Potentiodynamic measurements together with SEM were used to analyze susceptibility to pitting corrosion of 13CrNiMo plate metals. Volume fractions of austenite in tempered conditions affect pitting resistance. Characteristic potentials (critical pitting and repassivation) increase according to the retained austenite content. Results correspond to a structural refinement resulting from a double tempering procedure. A comparison is made with results from weld metal samples. The importance of this evaluation is to be able to determine pitting resistance, either in a service application, or in laboratory test programs.