Comparison of polyaniline primers prepared with different dopants for corrosion protection of steel

Abstract

Although it is well established that conducting polymers can provide corrosion protection to metals in aqueous environments, the processes involved are complex and the mechanisms are not fully understood. It is likely that the dopant used with the conducting polymer will affect the corrosion processes, since the dopant affects the polymer conductivity and permeability and the dopant is also released during galvanic coupling of the polymer to the metal. In this study, the aim was to determine whether the dopant used with polyaniline emeraldine salt affected the corrosion rate of coated steel when the polyaniline was used as a primer with a polyurethane or epoxy topcoat. The polyaniline emeraldine base was also considered as a comparison. The results showed that epoxy topcoated systems showed adequate corrosion protection for up to 2 years during immersion in 3.5% saline solution. Quantitative analysis of iron-dissolution rates showed distinct differences between polyaniline doped with different ions when used with a polyurethane topcoat. However, the emeraldine base produced the lowest iron-dissolution rate over the period tested.