High-temperature sulfide corrosion of cobalt-chromium alloys

The kinetics and mechanism of high-temperature sulfidation of cobaltchromium alloys were investigated. It has been found that the sulfidation rate of low-chromium alloys, up to 2% Cr, is higher than that of pure cobalt. The one-layer homogeneous scale on these alloys is a solid solution of chromium sulfide in cobaltous sulfide. In the case of alloys containing more chromium, up to 43%, sulfidation rate decreases gradually with chromium content, the scale consisting of two layers. The growth mechanism of scales as well as the influence of chromium concentration on sulfidation rate is discussed.This work was carried out under contract No. 03.10 coordinated by the Institute of Physical Chemistry, Polish Academy of Sciences.