Comparative analysis of the corrosion resistance of Bos taurus and Cocos nucifera reinforced 1170 aluminium alloy in chloride-sulphate solution

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Abstract Reinforced AA1170 aluminium alloy with particulates of Bos taurus (BT) and Cocos nucifera (CN) (0% to 20% wt. concentration) was evaluated for their corrosion resistance properties in 3.5% NaCl and 0.05 M H2SO4 solution by potentiodynamic polarization, open circuit potential analysis, potentiostatic analysis, optical and scanning electron microscopy and x-ray diffractometry. Results showed corrosion rate of monolithic aluminium alloy (0% particulate wt. concentration) from both electrolytes (3.5% NaCl and 0.05 M H2SO4) are 0.204 and 0.259 mm/y. Corrosion rate of BT reinforced composites from both solutions decreased with respect to BT particulate concentration to 0.087 and 0.216 mm/y at 20% BT. Whereas corrosion rate of CN reinforced composites decreased to 0.161 mm/y in 3.5% NaCl and increased to 0.434 mm/y in 0.05 M H2SO4 at 20% CN concentration. The most passivated aluminium composites from polarization plots occurred 5% BT and CN particulate concentrations. Increase in particulate concentration results in vulnerability to localized corrosion. Open circuit potential plots show the presence of the particulate reinforcements increased the thermodynamic instability of the surface properties of the composite and its exposure to active-passive transition behavior. Optical and scanning electron microscopy indicates significant improvements in the corrosion resistance of BT and CN particle reinforced aluminium compared to the unreinforced alloy were significant surface deterioration, pitting corrosion and intergranular corrosion were presence. X-ray diffractometry showed the phases identified for BT particle reinforced composite (Al2O3, CuS2, ZnS2, ZnCO3 and CuO2) significantly enhances it corrosion resistance compared to the monolithic and CN particle reinforced composite.

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