Influence of Iron and Silicon: Pitting Corrosion Characteristics of Aluminum^⋆

This work was undertaken to determine the influence of iron and silicon upon the pitting characteristics of aluminum. Iron and silicon in amounts from 0.05 to 0.7 percent, alone and in various combinations was added to commercial purity (99.75 percent Al) and super purity (>99.99 percent Al) aluminum. The addition of iron at any level increases the pitting probability of super purity aluminum whereas no significant increase occurs for the commercial purity aluminum. The addition of silicon to super purity aluminum in amounts of 0.3 percent and greater increases the pitting probability whereas no significant increase occurs for commercial purity aluminum. The probability of pitting of commercial purity aluminum is 2.5 times that of the super purity aluminum at corresponding iron and silicon levels. The addition of iron and/or silicon increases the rate of pitting of super purity aluminum but has little effect on the rate of pitting of commercial purity aluminum.