Methods for evaluation of corrosion rate on magnesium alloys: a review

The major drawback of some magnesium alloys is their low corrosion resistance. Therefore, the evaluation of corrosion resistance is a critical factor in developing new alloys and surface treatments. The techniques employed for the determination of corrosion rate include mass loss assessment, hydrogen evolution, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). However, there are still difficulties in precisely estimating this parameter in Mg alloys. In this review, the reported applications, advantages, and disadvantages of the techniques mentioned above were analyzed. On the other hand, a large number of corrosion rate values reported for various Mg alloys in 3 different media (NaCl, Hanks´ solution and SBF), using mass loss, hydrogen evolution, and PP, were compared and analyzed. Generally, corrosion rates obtained from mass loss are higher than those obtained from hydrogen evolution. On the other hand, it is not possible to obtain correlations between corrosion rates obtained from PP and those obtained from mass loss and hydrogen evolution. Even more, dissimilar corrosion rate values are reported for the same alloy, implying that the measuring procedures are not well standardized.