Heat-Affected-Zone Corrosion Behavior of Carbon-Manganese Steels

The effect of heat-affected-zone (HAZ) microstructure and base plate composition on HAZ corrosion was investigated in a series of CMn Steels in 0.5 N NaCI using micro-electrode and constant potential anodic dissolution testing. Ten different compositions of steels were used in this study. It was determined that there was no systematic effect of optical microstructure of the coarse grain region on HAZ corrosion. It was found that increasing the Mn content in all the steels tested increased the depth of the corrosion groove in the HAZ. Nb addition to the base compositions had little effect on HAZ corrosion in the higher carbon steels tested (0.12 wt%), but increased the HAZ corrosion in the lower carbon (0.06 wt%) steels. It was postulated that severe HAZ corrosion was the result of soluble Mn and Nb in the HAZ.