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

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 NaCI solutions; however, this decrease was 20.457.1 % 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 800 degrees C 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 degrees C and stirred for 6 mins, based on the lower crystallite size of alpha-Al phase.