A Study on the Corrosion and Tribocorrosion Behavior of Al-30 Vol.% B4C Composite Produced by Mechanical Milling and Hot Pressing

The present work aims to study the corrosion and tribocorrosion behaviors of pure Al and Al-30 vol.% B4C fabricated by a combination of mechanical milling and hot-pressing processes. Structural analysis and phase composition of the pure Al and the Al-30 vol.% B4C composite were evaluated by field emission-scanning electron microscopy and x-ray diffractometry, respectively. The corrosion behavior was investigated using electrochemical impedance spectroscopy and potentiodynamic polarization in a 3.5 wt.% NaCl solution. Tribocorrosion tests were performed under an open-circuit potential in the same solution with a ball-on-flat configuration, and Al2O3 balls were used. Electrochemical studies revealed that the composite with 30 vol.% B4C presented lower resistance to corrosion as compared to the pure Al evidenced by a decrease on the corrosion potential, an increase on the corrosion current density and a smaller diameter of the semicircle presented in the Nyquist diagram. The results from the potentiodynamic polarization measurements showed that pure Al corroded at 58% slower rate when compared to the corrosion rate of Al-30 vol.% B4C composite. However, tribocorrosion tests showed that B4C particle addition to the Al matrix decreased the wear volume of the resulted composite from 1.48 to 0.03 mm(3).