Sol–gel coating to reduce 1.25Cr–0.5Mo steel oxidation at 700 °C: Catalyst type effect

With the use of sol–gel it is possible to apply zirconia coatings to reduce high temperature oxidation of steel. Some limitations of this technique are high hydrolysis rates and the formation of cracks during the drying stage. In this work, the mole ratio of zirconium butoxide to ethylacetate, and the nature of the catalyst were varied. SEM-EDX was used to evaluate the continuity of the zirconia coatings, and thermo-gravimetric analysis for the oxidation rate of coated samples. Thin and continuous coatings were obtained. With a basic catalyst, the coatings were crack-free and presented lower oxidation rate than acid-catalyzed coatings.

Research highlights
► Basic catalysts promote the formation of non fragmented sol–gel coatings.
► Controlling the concentration of the precursors, coating cracking is reduced.
► Crack-free zirconia coatings reduce the oxidation rate of low alloy steel in 62%.