Surface micro-dimple effect and electrochemical corrosion behaviors of AZ31B magnesium alloy treated by laser

In order to study the influence of laser-induced micro-dimple on electrochemical corrosion behaviors of AZ31B magnesium alloy, samples are processed with optical fiber laser to get specific microdimple. The surface profile, diameter and depth of the micro-dimple are characterized by Axio CSM 700 and the electrochemical polarization curves are investigated by electrochemical work station. The results indicate that with the increment of laser power, the depth and diameter of micro-dimple increase but ablation occurs around the micro-dimple. The diameter of micro-dimple does not change significantly while the roundness improves with the number of processing increasing. Comparing with the untreated specimen, the corrosion potentials are improved by -33, 40, 26 mV and the self-corrosion currents decrease to 91.93%, 92.09%, 91.19% with laser powers of 6, 10, 16 W respectively under the same micro-dimple density condition. A better corrosion resistance is obtained with laser power of 10 W. For the same laser power condition, the corrosion potentials are improved by 21, 40, 56 mV and the self-corrosion currents decrease to 92.22%, 92.09%, 94.05% with the micro-dimple densities of 1.5%, 2.5%, 5.0% respectively comparing with the untreated specimen. Besides, the increasing of micro-dimple density leads to a better corrosion resistance of AZ31B magnesium alloy in the density zone of the experiment. ©, 2015, Science Press. All right reserved.