Use of Polarization Methods in the Determination of the Rate of Corrosion of Aluminum Alloys in Anaerobic Media

Abstract

Tafel-type cathodic polarization curves were obtained for aluminum alloys corroding in anaerobic acid and food media. The overvoltage-intercept method was found to give corrosion currents equivalent to the measured rates of hydrogen evolution. Tafel-type anodic polarization curves could not be obtained. Anodic polarization curves calculated from cathodic polarization data in the vicinity of the corrosion potential gave Tafel slopes which were identical to the cathodic Tafel slope, within 20%, in each individual case. On using suitable values for the Tafel slopes in the Stern and Geary equation, the polarization resistance method likewise gave corrosion currents in good agreement with measured rates of hydrogen evolution. This investigation arose from the need for a sensitive method of determining the instantaneous corrosion rate of aluminum in anaerobic media under conditions where it is not possible to measure such quantities as weight loss and hydrogen evolution.