Influence of hydrogen peroxide addition on the corrosion of carbon steel by concentrated sulphuric acid

CIM Bulletin, Vol. 80, No. 903, 1987

C.M. DAVIDSON and D.J. DREXLER Research Centre, C-I-L Inc. Mississauga, Ontario

Sulphuric acid treated with hydrogen peroxide to destroy organic contaminants could conceivably show increased cor-rosivity toward carbon steel shipping and storage vessels, caused by the persistence of a peroxide residual. This paper describes work performed to determine the effect of 0-200 ppm hydrogen peroxide on the corrosion of carbon steel by 93% and 98% sulphuric acid at room temperature (23 °C) and 50°C. Steel electrodes were exposed to acid containing several peroxide levels (0, 45, 100 and 200 ppm) for up to two weeks. Specimens were removed at intervals and weight loss, open circuit potential, depth of metal loss and residual peroxide concentration recorded. Hydrogen peroxide decomposes considerably over two weeks in iron-contaminated sulphuric acid. Initial peroxide concentrations > 100 ppm suppress corrosion, but the effect is lost when concentration decays below about 60 ppm. Sustained peroxide levels in the range below 60 ppm may increase corrosion rates. These phenomena are interpreted by analogy with anodic passivation.
Keywords: Hydrogen peroxide, Carbon steel, Corrosion , Contaminants.