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Corrosion resistance of nanosilicasilicate conversion coatings on aluminum prepared by the dip immersion method

Abstract Nanosilica modified potassium silicate conversion coatings were deposited on the surface of 2024 aluminum alloy by the dip immersion method, and the effect of the immersion time was studied on anticorrosion behavior of coatings. The corrosion behavior of coatings was examined by means of electrochemical impedance spectroscopy, potentiodynamic polarization and surface analyzing techniques. The coated samples showed a significant decrease in corrosion rate. The experimental results indicated that the increase in silica ratio led to an increasing in the corrosion resistance of aluminum. Immersion time in potassium silicate solution showed a significant effect on silicate conversion coating and higher corrosion resistance was obtained with 400 s immersion. This behavior can be related to increasing the silicate coating continuity which formed on the surface. The coating performance evaluated in acidic and basic NaCl solution as well as the results showed the corresponding stability of nanosilica modified silicate conversion coating in these solutions.