Corrosion behaviour of maize husk reinforced aluminium (1070) metal matrix composites in chloride-sulphate solution

Abstract

The effect of maize husk (MH) particulates on the corrosion resistance of 1070 aluminium alloy (AA70) matrix at 5% and 15% wt. content, and 150 µm and 300 µm particle size (AA70/MH composites) was studied in 3.5% NaCl, 0.0125 M H2SO4 and 3.5% NaCl/0.0125 M H2SO4 solutions. Potentiodynamic polarization technique, open circuit potential measurement, weight loss analysis, optical microscopy characterization, x-ray fluorescence and x-ray diffractometry were used for the investigation. Results show increase in MH %wt. content and particle size decreases the corrosion rate of AA70/MH composite. Data from potentiodynamic polarization and weight loss analysis shows AA70/MH composite at 15% wt. content and 300 µm particle size exhibited the lowest corrosion values of 0.135 mm/y, 0.156 mm/y and 1.445mm/y, and -0.00043 mm/y, 0.00104 mm/y and 0.00218 mm/y in 3.5% NaCl, 0.0125 M H2SO4 and 3.5% NaCl/0.0125 M H2SO4 solutions. Optical representative images of the composites showed the presence of micro-pits on samples from NaCl solution, macro-pits and extensive surface deterioration from H2SO4 solution and combined localized and total surface deterioration from NaCl-H2SO4 solution. Weight loss plots showed oxide formation significantly influenced the corrosion behavior of the alloys with respect to time. Open circuit potential plots showed AA70/MH composite at 5% wt. content and 150 um particle size was the most electronegative with the highest thermodynamic tendency to corrosion. Significant X-ray diffraction peaks from AA70/MH composite at 15% wt. content and 300 µm particle size showed the presence of corrosion resistant phase compounds of Al2O3 and Al(ZnS2) before and after corrosion.