Surface activation of aluminium alloy sacrificial anodes by IrO2

Several studies have been focusing on alloying and structural modifications of aluminium alloy sacrificial anodes. The present work explores and evaluates the feasibility of effective aluminium activation in Al+5% Zn alloy anodes by IrO2 surface coatings. The IrO2 coatings were made on the anode by thermal decomposition of IrCl3 in presence of air. The anodes were found to possess good surface interaction, low surface resistivity and facilitate interlayer diffusion of aluminium ions. The anodes showed excellent galvanic performance under different experimental conditions in 3% NaCl solution when they were indented to protect steel. The porous, cracked IrO2 layer was found to persist on the electrode surface even after the electrode size was substantially reduced due to long period of galvanic exposure. The promising anodes were found to be cost effective also.