Corrosion and corrosion inhibition of alumina particulate aluminium alloys metal matrix composites in neutral chloride solutions

A study of the corrosion behaviour and corrosion inhibition of AA 6061 and AA 2014 metal matrix composites (MMCs) reinforced with alumina particles, during exposures to 0.1 M NaCl solution is reported. Many tungsten and molybdenum-containing inorganic salts were tested as corrosion inhibitors, but only ammonium tetrathiotungstate afforded good inhibiting properties, particularly towards the AA 2014-based MMC. The corrosion behaviour of the composites in uninhibited or inhibited solutions was compared by different techniques to that exhibited by the corresponding matrices. The techniques adopted included weight loss measurements, electron probe microanalysis (EPMA), scanning electron microscopy (SEM), linear polarization resistance measurements, polarization curve recordings and current noise analysis. The analysis of the current fluctuations showed that different patterns of the time records were obtained during pit initiation, stable pitting and general corrosion. The power spectrum density plots exhibited f(-alpha) trends, with alpha values around 20 dB decade(-1) when corrosion was mainly localized in pits, while values tending to zero were measured when general corrosion became dominant.