Effect of metal ions on corrosion inhibition of pimeloyl-1,5-di-hydroxamic acid for steel in neutral solution

The influence of metal ions on the adsorption process and corrosion inhibition of pimeloyl-1,5-di-hydroxamic acid (C7) on carbon steel surface in neutral solutions has been investigated by surface analytical and electrochemical techniques. Effective corrosion inhibition given by C7 in the presence of Zn2+ and Ni2+ is believed to be associated with the ability of the hydroxamic acid to form stable slightly soluble complexes with these cations. The influence of the metal ions on the inhibition efficiency is primarily related to the stability constants of C7-cation complexes. Magnesium has no effect on the inhibition performance as it has low stability constant with C7. It was found that the inhibition by C7/cation mixtures depends greatly on the molar ratio and immersion time.