Abstract
The corrosion resistance of chemically treated aluminum was investigated from following experiments in 0.5M NaCl at 80°C. Changes of the film structure were revealed from the weight gain of specimens (γl-layer) during immersion in 0.5M NaCl at 80°C. IRRS measurment and SEM observation showed the composition of the film and the surface appearance of the specimens respectively. The corrosion resistance of chemically treated aluminum and aluminum alloys have been examined by measuring the polarization curves.
These results showed as follows; The weight of γl-layer on 99.99% Al and Al-Mg alloy were greater than that of Al-Zn alloy. In such a corrosive condition even at 80°C, the pitting potential of 99.99% Al and Al-Mg alloy was more noble than that of Al-Zn alloy. These results indicated that the corrosion resistanse of the specimens was responsible for the formation of the γl-layer. IRRS of the oxide film proved the formation of the Al2O3 containing amorphous hydroxide when specimens was immersed in 0.5M NaCl at 80°C for long duration. SEM observation revealed that the film grew into needle like microscopic structure with increasing immersion time in 0.5M NaCl at 80°C.
