Improving the corrosion resistance of epoxy/polyamide coatings

Reseachers improved the protective performance of solvent-borne epoxy/polyamide coatings formulated with zinc phosphate anticorrosion pigment through the addition of 2-mercaptobenzimidazole as an organic corrosion inhibitor.

Corrosion resistance of bare mild steel in NaCl solution was improved by the mixture. Source: Jurec / -

In addition to determining the optimum percentage of mercaptobenzimidazole, the electrochemical impedance spectroscopy data could show the influence of inhibitor concentration on the epoxy behaviour within 35 days of immersion in 3.5 wt% NaCl solution.

Deposition of protective layer

The improved corrosion protection and adhesion strength in the presence of the pigment and inhibitor were connected to the deposition of a protective layer at the coating/substrate interface which might limit active zones for electrochemical reactions. The precipitation was confirmed using electrochemical impedance spectroscopy, polarization curves and SEM/EDX surface analysis.

The study is published in: Progress in Organic Coatings, Volume 86, September 2015, Pages 117-124.

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