Analysis of SiC grain size variation and NaCl concentration on the corrosion susceptibility of AA1070 aluminium matrix composites

Analysis of the impact SiC grain size at 10% wt. on the corrosion resistance of AA1070 aluminium matrix composites was studied in Cl- anion containing dilute H2SO4 solution. Studies were performed with potentiodynamic polarization and open circuit potential (OCP) measurement. Optical microscopic studies were performed on the corroded matrix composites. Results show that the corrosion susceptibility of the composites increased proportionately with increase in Cl- ion concentration. The matrix composites at 3 um and 9 um SiC grain size exhibited the lowest corrosion rate values in comparison to the base alloy and composites with larger SiC grain sizes. OCP values for the matrix composite at 0 mu m SiC in the acid solution (0.25M H2SO4/0% and 0.25% NaCl) was the most electronegative due to lower thermodynamic stability than matrix composites with larger SiC grain sizes. Optical microscopic studies show that corrosion was mainly localized for all specimens tested due to pitting at low Cl- ion concentration in comparison to general corrosion for the metal substrate and total destruction of the matrix composite morphology at higher chloride concentration. Results of statistical analysis through ANOVA showed that SiC grain sizes are more relevant than NaCl concentration in evaluation of the corrosion susceptibility of the matrix composite.