Effect of pH on Coatings Used to Protect Aluminum Beverage Cans

This study investigated the performance of epoxy-free coatings used to protect aluminum beverage cans from corrosion in acidic solutions. Electrochemical Impedance Spectroscopy and cyclic voltammetry tests were used to distinguish good and bad coatings by monitoring the corrosion of the underlying aluminum. The goal of this work was to understand how coatings protect the aluminum in spite of holes and holidays in the coating. Bad coatings were made by introducing pinholes. Three scenarios were found to hinder or stop corrosion: change from neutral to acidic pH, de-aeration using carbon dioxide gas, and the formation of bubbles. This study concluded that the formation of bubbles on the exposed surface of the aluminum, in concert with the coating, protects the aluminum from corrosion in acidic solution.