Detection of the Initiation of Pitting by the Higher Harmonic Content of Electrochemical Response

Abstract

Abstract The use of the higher harmonic content in the electrochemical current response to an applied 30 mHz sinusoidal potential for detecting the onset of pitting corrosion in Al 8090 and type 304 stainless steel has been evaluated. The level of higher frequencies relative to the fundamental in the AC current signal increases just when pitting initiates. However, the relative intensity of the higher frequency component decreases as the rate of pitting increases contrary the prediction of a simple model. This decrease with increasing pitting current is attributed to the increasing importance of the effect of IR drop.