Galvanic corrosion behaviour of iron coupled to aluminium in NaCl solution by scanning eectrochemical microscopy

Abstract

Scanning electrochemical microscopy (SECM) was used to sense the concentration of ions in 0.1M NaCl aqueous solution at the iron-aluminium couple. The SECM measured the concentration of ions relevant to the corrosion processes. The electrochemical behaviour of galvanic Fe/Al coupling was investigated as a function of time using SECM microelectrode tip. SECM amperometric line scan curves were obtained over the Fe/Al at a constant distance. In the first case the chemical species participating in the corrosion reactions at the sample are detected at the SECM-tip by applying appropriate potential values to the microelectrode. The release of Al³⁺ into the solution from local anodic surface, as well as the consumption of dissolved oxygen at the corresponding cathodic surface was successfully monitored. The results revealed that the galvanic couple where Fe/Al is close to each other will show lower corrosion rate due to the formation of corrosion products on the metal surface with further increase in exposure times.