Gas Corrosion of Chromium-Manganese Steel in Atmospheres with Low Oxygen Partial Pressure

Abstract

Studies were conducted on the kinetics and mechanism of oxidation of chromium-manganese steel under partial oxygen pressure pO2from 10-11to 10-2Pa at a temperature of 1173 K. The low oxygen partial pressure was produced in a gas mixture of CO-CO2and helium containing 0.2 ppm of oxygen. The kinetics of oxidation was examined by thermogravimetry using a thermobalance made by Setaram Company. Scale growth mechanism was determined with the use of markers. The oxidation products were analyzed by scanning electron microscopy (SEM, EDS). It was found that at low partial pressure of oxygen, MnO oxide was forming on the steel surface. From an analysis of the curves of the steel weight growth per unit surface in function of time it followed that the oxidation assumed a parabolic course. A relationship has been determined between the coefficient of self-diffusion of manganese in MnO and the oxygen partial pressure.