Effects of NaCl concentration on galvanic corrosion behavior of aluminum alloy A5052/carbon steel SS400 couple

Abstract

In this study, galvanic corrosion of an Al-Mg alloy A5052 and carbon steel SS400 couple in aqueous NaCl solution was investigated. Galvanic corrosion experiments were performed for 259.2 ks in aqueous NaCl solutions at various NaCl concentrations ranging from 5 mol/m3 to 500 mol/m3. Galvanic current and corrosion potential of the couple were measured during immersion in the solutions. Corrosion potentials measured during the immersion in various concentrations of NaCl were almost constant for 7.2 ks and shifted in the less noble direction with increasing NaCl concentration. Galvanic currents between A5052 and SS400 showed positive values during the immersion in the solutions, indicating that A5052 side was basically an anode. These results indicated that galvanic corrosion between A5052 and SS400 in the early stage of immersion progressed under a diffusion-limiting condition for the reduction of dissolved oxygen on the SS400. However, galvanic corrosion behavior changed with immersion time in NaCl solutions of 5 and 50 mol/m3; the change in the galvanic corrosion behavior was attributed to the change in the anodic polarization behavior both on A5052 and SS400. The galvanic corrosion behavior of the A5052/SS400 couple in NaCl solutions were explained in detail.