This paper describes the mechanism behind the anti-corrosion behavior of mixed metal oxide (MMO) dispersed alkyd resin coating obtained via high energy ball milling. MMOs such as TiO2·Fe2O3 TiO2·ZnO and TiO2·NiO are prepared by adopting sol-gel and gel combustion techniques. The crystallite size and the morphology of the MMO pigments are analyzed using XRD and FESEM respectively. The XRD pattern reveals that the synthesized pigments are highly crystalline in nature. The composition and purity of the pigments are analyzed by EDX analysis. 20 wt. % of prepared MMO is dispersed in alkyd resin along with suitable non-toxic additives to prepare alkyd coating. The obtained suspension is coated and dried over A36 structural steel by brushing method. The corrosion inhibition properties of the coating are studied by potentiodynamic polarization measurements and wet corrosion techniques. The specimens coated with alkyd resin containing MMO pigments exhibit higher corrosion protection efficiencies of 98.18% (TiO2·Fe2O3), 99.19% (TiO2·ZnO) and 86.15% (TiO2·NiO) respectively in different acid media. Response surface methodology in combination with the Box-Behnken design is used to optimize the best corrosion inhibitive pigment in the coating in different kinds of acid. ANOVA indicates the influencing factor with a confidence level of 0.991 by comparing the F-value obtained with F-test value. The optimized results show that the coating consisting of TiO2·ZnO displays minimum weight loss (2.4 mg in 0.1 N HNO3), with high inhibition efficiency (99.48%) and lower corrosion rate (2.34 mpy).

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Available online 1 June 2017