CORROSION BEHAVIOR OF SS304 IN HYDROGEN CHLORIDECONTAINING ENVIRONMENTS

Abstract

The corrosion behaviour of stainless steel SS304 was investigated in three major aqueous environments, namely dry, water-saturated and free-water conditions and in two different methanol environments, namely dry and watersaturated environments with 99% methanol +1% water. The sulfuric acid and sodium chloride reaction generated hydrogen chloride gas in all the experiments. An inert carrier gas such as argon pushed the hydrogen chloride gas to flow over desiccants to make the latter dry. The dry hydrogen chloride gas would then flow into the second flask to which a pre-weighted stainless-steel specimen was exposed at ambient conditions for 48 hours. The specimen was retrieved and subjected to the surface and chemical analysis using Scanning Electron Microscopy (SEM)/EDAX. The presence of chloride would affirm the adsorption of chloride ions on the metal surface and vice versa. The specimen was then weighted to determine the corrosion rate. The results suggested that stainless steel would not corrode in dry hydrogen chloride gas. However, when saturated with moisture, its corrosion rate would increase by about one order of magnitude. In a free-water environment, the corrosion rate would triple. Hydrogen chloride gas would react with moisture or water, turning it into hydrochloric acid. Hydrochloric acid is a reducing acid that attacks the Cr2O3 layer, leading to general and/or localised corrosion. The presence of methanol increased the corrosion rate of stainless steel by a factor of three to four.Keywords: methanol, stainless steel, localised corrosion, methyl chloride