Microstructural corrosion behavior of a cold-worked steel in a sour environment

The effect of cold-working mild steel was investigated on its corrosion characteristics. Pipeline steel was subjected to a mixed sour gas and brine environment. The amount of cold working was varied from 0 to 70% in 10% increments. Surface attack was identified using both light and electron microscopy. Corrosion was measured using an electrochemical technique and a method to separate out hydrogen embrittlement effects is suggested. The corrosive attack was correlated with respect to the underlying microstructure and was monitored as a function of time to determine the microcorrosion mechanisms. The microcorrosive attack of hot-rolled mild steel is a general corrosion process whereas the microcorrosive attack of cold-worked steel is a localized corrosion process. This localized corrosion of coldworked steels is a result of surface deformation slip caused by cold working.