Electrochemical Characterization of Anti-Corrosion Coatings Formed on 6061 Aluminum Alloy by Plasma Electrolytic Oxidation in the Corrosion Inhibitor-Enriched Aqueous Solutions

The 6061 aluminum alloy was surface-treated by plasma electrolytic oxidation (PEO) in silicate-and borate based electrolyte systems. The authors attempted to incorporate selected corrosion inhibitors (8-hydroxyquinoline, 2-mercaptobenzothiazole, poly(acrylic acid) with molecular weights of 1800 and 450,000 g mol(-1), and acrylic acid) into the oxide coating to provide long-lasting protection of the substrate. These inhibitors were either added directly to the electrolyte for the treatment or loaded into the coatings through a sequential PEO procedure. Electrochemical corrosion tests showed that acrylic acid-modified coatings provided the best protection. In general, of the two methods, the sequential PEO gave more reproducible anti-corrosion effects.