Effect of sintering temperatures on corrosion and wear properties of sol–gel alumina coatings on surface pre-treated mild steel

Sol–gel alumina coatings were developed on the surface pre-treated (zinc-phosphated) mild steel substrate and subsequently sintered at 300 °C, 400 °C and 500 °C. The alumina sol was synthesised using aluminium iso-propoxide as a precursor material. FTIR of the boehmite (AlOOH) gel sintered at above-mentioned temperatures was employed to identify the presence of various functional groups. The microstructural features and the phase analysis of the sol–gel coated specimens were carried out using SEM and XRD respectively. The corrosion resistance of the sol–gel alumina coatings was evaluated by electrochemical measurement in 3.5% NaCl solution at room temperature. The abrasive wear behaviour of the sol–gel coated specimens was measured in two body (high stress) conditions. The experimental results revealed that the sol–gel coated specimen sintered at 400 °C has superior wear and corrosion resistance properties as compared to the sol–gel coated specimen sintered at 300 °C. However, the sol–gel coated specimen sintered at 500 °C has exhibited a very poor corrosion and wear resistance properties. Poor performance of the sol–gel coatings sintered at 500 °C could be explained to be due to (i) the presence of numerous cracks (ii) absence of organic groups in the coating.