Technical Note: Crevice Corrosion Rate Measurement of Aluminum Alloys by Linear Polarization Method

Electrochemical techniques are often employed to evaluate crevice corrosion. Critical potential values such as crevice corrosion potential,^1,2  crevice protection potential,³  or difference potential⁴  have been proposed to indicate a crevice corrosion tendency. From a practical point of view, it is useful to know the corrosion rate under crevices. The linear polarization method, widely used in order to obtain corrosion rates of metals, shows good accuracy for the general corrosion.⁵  However, the reliability of this method seems to be poor in assessing corrosion rate of aluminum in neutral water because of an instability of polarization potential during measurement.⁶  This instability is considered to be due to an existence of thick oxide film on the surface of aluminum.⁷  In the case of crevice corrosion, however, the corroding surface is exposed to the solution with reduced pH and enriched ion concentration and, consequently, is expected to have...