The outward–inward growth behavior of microarc oxidation coatings in phosphate and silicate solution

Abstract Microarc oxidation (MAO) coatings have a unique outward–inward growth behavior, which is crucial to the dimensional matching of precision-matching parts after surface treatment. Here, a notably different outward–inward growth behavior of MAO coatings was observed in phosphate solution and silicate solution, respectively. The results indicate that the outward-growth dimension of MAO coating in Na 2 SiO 3 solution is notably larger than that in (NaPO 3 ) 6 solution, especially at the initial stage of MAO treatment, but as an increase of oxidation time, the inward-growth behavior enhances in both solutions. It is considered that the different adsorptive capacity of solute anions leads to the various outward–inward growth behaviors of MAO coatings in phosphate solution and silicate solution.