CORROSION RESEARCH ROUND‐UP

U.S.S.R. Effect of pH value on iron corrosion. The solubility of iron in media of sufficiently high acidity proceeds mainly through hydrogen depolarisation and without formation of compounds soluble only with difficulty; and the role of pH should be determined chiefly through its effect on hydrogen separation. In work on the nature of the pH effect on corrosion of iron in the presence of inhibitors, tests were made with both pure hydrochloric acid (HCl) and also in the presence of additives: anthranilic acid and tetrabutyl‐ammonium sulphate (TAS). The corrosion rate was determined as usual by loss in weight and expressed in units of current density (amp./sq. cm.). Preliminary tests showed that only in weak solutions (pH 0.61 and 1.06) containing TAS was any divergence noticeable—in connection with the increased role of oxygen depolarisation — between results of quantitative and volumetric methods. Therefore in the present case the corrosion rate is calculated from the volume of separated hydrogen. The pH value was measured with a glass electrode and amplifier, and controlled both before and after test. The tests were made in an aero‐thermostat at 20° ±0.5° and each lasted 24 hr.