We report the fabrication of alumina (Al2O3) and silicon carbide (SiC) particulates reinforced Al metal matrix composites (Al MMCs) by stir casting method. The effect of reinforcement and heat treatment on the corrosion properties of Al matrix and r-Al MMCs were investigated by polarization, impedance and weight loss methods. Taguchi's experimental design method was employed to set the process parameters. In order to find the optimal process parameter levels, orthogonal arrays of Taguchi, the signal-to-noise (S/N) ratio, the analysis of variance (ANOVA), and regression analyses were employed. The analysis on the effect of these parameters on the corrosion rates has also been discussed. The results revealed that the rate of corrosion decrease with increase in the content of Al2O3 and SiC particulates in the r-Al MMCs. A significant enhancement in the corrosion resistance was observed with heat treated of Al alloy and its composites. The morphological analysis by SEM micrographs revealed the lesser formation of cavities due to corrosion upon the increase in Al2O3 content which would be beneficial for corrosive application.

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Ni 3 Ti and Ni 3 Ti+(Cr 3 C 2 +20NiCr) coatings were deposited on gas turbine based ASTM B265 titanium (Ti-15) and AISI 420 stainless steel (MDN-420) substrate materials using HVOF technique. Thermocyclic hot corrosion tests were carried out at 650 °C in molten salt environment of Na 2 SO 4 −40%V 2 O 5 for about 50 cycles. Thermogravimetric analysis was carried out to study the hot corrosion kinetics of uncoated and coated titanium and stainless steel substrates. The weight gain per unit area showed that the coated substrate materials displayed better resistance to hot corrosion when compared with that of uncoated substrate materials. The surface morphology of uncoated and coated substrate materials were analysed using scanning electron microscopy and elemental analysis. The formation of different types of oxides and compounds were analysed using x-ray diffraction. The uncoated substrates surface showed microspalling at several regions while coated substrates surface were composed of protective oxide layers. The presence of ternary NiCr 2 O 4 protective oxides on the surface of Ni 3 Ti+(Cr 3 C 2 +20NiCr) coated substrates leads to reduction in the diffusion of corrosive species inside the coating.