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

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 mu m and 300 mu m 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 mu m particle size exhibited the lowest corrosion values of 0.135 mm y(-1), 0.156 mm y(-1) and 1.445 mm y(-1), and -0.00043 mm y(-1), 0.001 04 mm y(-1) and 0.00218 mm y(-1) 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 mu m particle size showed the presence of corrosion resistant phase compounds of Al2O3 and Al(ZnS2) before and after corrosion.

Automated summary

This study investigates the effect of maize husk particulates on the corrosion resistance of 1070 aluminium alloy matrix. The results show that the corrosion rate of the alloy decreases with an increase in maize husk content and particle size. The composite with 15% maize husk content and 300μm particle size demonstrates the lowest corrosion values. Optical microscopy and x-ray diffraction analysis confirm these findings.