Effect of Sodium Silicate Concentration on Morphology of Ceramic Coatings Produced on Commercially Pure Aluminum Using Plasma Electrolytic Oxidation

Abstract

Microstructure of ceramic coatings formed on commercially pure aluminum by plasma electrolytic oxidation using different amounts of sodium silicate was studied. Analysis of chemical composition and microhardness measurements of the coatings were carried out to characterize the morphology of the coatings. The addition of sodium silicate (1–3 g/L) increased the thickness about 8 orders of magnitude and promotes the growth of the coatings. Chemical analysis of the coatings showed that with increasing sodium silicate concentration in the electrolyte from 1 to 3 g/L, the amount of manganese in the coatings was reduced ∼12%. The contribution of aluminum and silicon changed with a reciprocal relationship. When the concentration of Na2SiO3 changed from 1 to 2 g/L, the aluminium content was reduced about 26% and silicon increased about 80%. When the concentration of Na2SiO3 changed from 2 to 3 g/L, the aluminium content increased about 38% and the concentration of silicon reduced about 60%. The microhardness of the coatings was increased about 2 orders of magnitude by increasing the concentration of sodium silicate from 1 to 3 g/L.