Methods of measuring current transients due to solid particle impingement are presented. The processes involved form the basis of slurry erosion–corrosion, whereby the rate of wastage of a metal is greater than the sum of the separate erosion rate and the corrosion rate, when under exposure to a flowing solid/liquid slurry. The measurements are electrochemical in nature, backed up by a coupled acoustic emission sensor to detect slurry impact on the metal surface. Evidence is shown that it is possible to measure a threshold energy of the impacting slurry above which the passivating surface oxide is ruptured by erosion, and below which it is not. Some consequences of depassivation are discussed, and it is shown that depassivation of stainless steels by the impacting slurry can stimulate the formation of metastable pits in a chloride containing environment.