Development of Al-containing zinc-rich paints for corrosion resistance

The effect of Al addition on the corrosion performance of zinc-rich paints (ZRP) was investigated. Both electrochemical measurement and salt spray test were employed to evaluate the corrosion performance of ZRP with or without Al addition. The Al content as percentage of the total metallic components in the ZRP, investigated in this study, varied from 0 to 75 wt.%. The experimental results showed that protective nature of ZRP altered from cathodic protection to barrier former as the Al content was increased beyond 20 wt.%. The results from salt spray tests also revealed that the corrosion products were modified with the presence of aluminum oxide in the Al-containing ZRP. The amount of zinc white on the painted steel decreased as the Al content in the ZRP increased. The protectiveness, in terms of the time of red rust formation and cathodic protection, was reduced as the Al content was higher than 20 wt.%.