Corrosion Behavior of Aluminum in some Short-chain Carboxylic Acid solutions as a Simulant for Cooling Water in HVDC Transmission

Abstract

The corrosion law of Al in various acidic solutions at 25 °C was determined in this study. The pH of 0.1 mM solutions of different weak acids was measured by a pH meter. Electrochemical tests were carried out using the polarization curve method and EIS. The activation energy of Al corrosion in different weakly acidic solutions was calculated by thermodynamic analysis. The results showed that the Al corrosion resistance was lowest in the formic acid solution and highest in the n-butyric acid solution. That is, Al in the n-butyric acid solution exhibited the lowest corrosion current density, the largest charge transfer impedance and the highest corrosion activation energy. The corrosion products of Al mainly exist in the form of Al(OH)3 over a pH range between 3.7 and 4.7. The large anions in solution inhibit the ionization of weak acids and adsorb on the Al surface, thus inhibiting Al corrosion. The elucidation of the effect of anions on Al corrosion provides insight into the corrosion law of Al and a theoretical basis for identifying effective corrosion inhibitors.