Single particle impact experiments for studying particle induced flow corrosion

An experimental set-up for the investigation of particle induced flow corrosion is described. It allows high speed monitoring of the repassivation current transient resulting from the impingement of a single particle. High purity aluminium microelectrodes with a diameter of 125 μm were used as targets in a neutral acetate buffer. Zirconia spheres of similar diameter were impinged at a flow rate of 7 m s−1. After an activation period of about 6 μs the current reaches a peak current of 10 μA. The current returns to its initial base line within one millisecond. Subsequent ex situ investigation of the samples in a SEM allows linking the detected surface destruction to its current transient. A crater of some 20 μm diameter is observed that shows a nanoscopic substructure resulting from the nanostructure of the particle. Part of the repassivation charge must be determined by an extrapolation of the high field oxide growth. A comparison of the consumed charge to the microscopic observations gives insights into the destruction mechanisms.