Influence of pH value on the microstructure and corrosion behavior of carbon fiber reinforced magnesium matrix composites

The effect of pH value on the corrosion behavior and microstructural evolution of carbon fiber reinforced magnesium matrix (Cf/Mg) composites in NaCl solution were investigated. The results of the electrochemical test revealed that the corrosion current density of Cf/Mg composites in pH = 13 solution achieved 3.4 × 10−5 Am/cm2, which was one order and two orders of magnitude lower than that of pH = 7 solution (2.6 × 10−4 Am/cm2) and pH = 1 solution (1.1 × 10−3 Am/cm2), respectively. Electrochemical impedance spectroscopy (EIS) curves implied that the corrosion resistance of Cf/Mg composites was enhanced when the pH value increased. The microstructure of the Cf/Mg composites after corrosion in the solution with pH = 13 first appeared as some point-like bumps, and then gradually grew into a lamellar structure. The corrosion mechanisms and microstructural evolution of the Cf/Mg composites were systematically discussed.