The Effect of Mill Scale and Magnetite on Crevice Corrosion Resistance of Carbon Steel in Concentrated Lithium Bromide Solutions
Atsushi NONAKA and Hidemasa NONAKA
Abstract:In order to evaluate the effect of mill scale and magnetite on crevice corrosion resistance of carbon steel which is used as a regenerator vessel material in the absorption refrigeration cycle, immersion test and electrochemical measurements of carbon steel in concentrated lithium bromide solution were carried out. As a result, when there was mill scale on surface of carbon steel and there existed magnetite as impurity in concentrated lithium bromide solution, probability of crevice corrosion became higher. It was supposed that reason was as follows: the existence of mill scale on carbon steel mainly restrained anodic reaction of iron and the existence of magnetite promoted cathodic reaction on the surface of carbon steel. Therefore, spontaneous potential of carbon steel became nobler than its repassivation potential of crevice corrosion. It was found that adding reducing agent to the solution was very effective for crevice corrosion protection. Key Words:Carbon steel, Magnetite, Mill scale, Corrosion inhibitor, Crevice corrosion, Lithium bromide, Absorption cycle