An investigation of corrosion behavior of Al–B₄C nanocomposites in various corrosive solutions

Abstract

In this paper, the corrosion behavior of Al-B₄C nanocomposites made by stir casting is investigated. The corrosive environments included 0.1 M HCl, 0.6 M NaCl, 0.03 M H₃BO₃, and 2 M NaOH solutions. Both the optical microscopy and the field emission scanning electron microscopy methods were used for the microstructural investigation. The X-ray diffraction and the energy dispersive spectroscopy techniques were utilized to detect phases. Tafel polarization results showed that the corrosion rate for the Al-B₄C nanocomposites reduced by about 94.0 -99.7% in comparison with the aluminum alloy in 0.1 M HCl and 0.6 M NaCl solutions; however, this decrease was 20.4 - 57.1% in 0.03 M H₃BO₃ solution. Moreover, the electrochemical impedance spectroscopy results demonstrated that for nanocomposites the total increase in the charge transfer resistance increased to 80.7% compared to the aluminum alloy in 0.1 M HCl solution after 72 h. The Al-B₄C nanocomposite that was stirred for 6 mins at 800⁰C exhibited higher corrosion resistance than other samples after 72 h in 0.6M NaCl. However, the sample suggested for all utilized corrosive solutions was the nanocomposite made at 750 ⁰C and stirred for 6 mins, based on the lower crystallite size of a-Al phase.