Abstract
Pitting corrosion behaviors of Al-Fe alloys in 0.1M NaCl solution were investigated by measurement of corrosion potential and the pH value of bulk solution. The corrosion potential changes from -0.6V vs. Ag/AgCl in the early stage (<100h) to -0.8V in its late stage (>200h). This shift of corrosion potential to less noble potential occurs due to the increase of Cl- ion concentration in the pit. The pH values of bulk solution changes from 5.0 to 6.0-6.5 during the long range process. The following reactions occur in the later stage;
Fe(OH)2+2H+→Fe2++2H2O
Fe(OH)2+2H++2e→Fe+2H2O
Iron which exists in the form of FeAl3 plays not only a statistical role of cothodic site where the oxygen reduction occurs, but also a dynamic role in which iron in FeAl3 changes chemical forms, e. g. ferrous iron, ferrous hydroxide and deposited iron in the later stage of corrosion process.
