Optimization of surface properties of plasma electrolytic oxidation coating by organic additives: A review

© 2021 by the authors. Licensee MDPI, Basel, Switzerland.Plasma electrolytic oxidation (PEO) is an effective surface modification method for producing ceramic oxide layers on metals and their alloys. Although inorganic electrolytes are widely used in PEO, the organic additives have received considerable interest in the last decade due to their roles in improving the final voltage and controlling spark discharging, which lead to significant improvements in the performance of the obtained coatings. Therefore, this review summarized recent progress in the impacts of organic additives on the electrical response and the plasma discharges behavior during the PEO process. The detailed influence of organic additives, namely alcohols, organic acids, organic amines, organic acid salts, carbohydrate compounds, and surfactants on the corrosion behavior of PEO coatings is outlined. Finally, the future aspects and challenges that limit the industrial applications of PEO coating made in organic electrolytes are also highlighted.