Electrochemical characterization of anti-corrosion coatings formed on 6061 aluminum alloy by plasma electrolytic oxidation in the corrosion inhibitor-enriched aqueous solutions

•PEO in the borate bath brought more anti-corrosion effect than in the silicate bath.•The PEO oxide coatings were modified with the use of corrosion inhibitors (CIs).•The single-step method was the addition of 0.1 g L−1 of a CI to the Si or B bath.•The sequential method was the dipping of the coating in a CI solution and DC PEO.•Mullite, α- and γ-Al2O3 were detected in the PEO oxide coatings.•Acrylic acid was the most effective CI in both single-step and sequential methods. 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. [Display omitted]