Mesa Corrosion Attack in Carbon Steel and 0.5% Chromium Steel

Local breakdown of protective corrosion films may result in rapid local attack or mesa corrosion attack during CO{sub 2} corrosion of carbon steel. The factors affecting formation and local breakdown of protective corrosion films were studied in a series of flow loop experiments performed at 40--80 C with pH 5.8, 1.8 bar CO{sub 2} partial pressure, high iron content in the water and flow rates 0.1--7 m/s. Carbon steels with or without chromium and nickel additions up to 1% were tested. Addition of 0.5% chromium in the steel was found to reduce the tendency for severe mesa attack in carbon steels during CO{sub 2} corrosion significantly. Deep mesa attack did not occur in steels with 0.5--1% Cr in experiments at 80 C and pH 5.8. Protective corrosion films reform more easily in the chromium containing steels, making localized attack less dangerous in chromium containing steels than in unalloyed carbon steels.