Effect of Addition of Silver and Chilled Casting on Corrosion Behavior of AZ91 Magnesium Alloy

In the present study, the effect of alloying AZ91 magnesium alloy with 0.4 wt.% silver as well as chilled casting on the corrosion response of different casting conditions was investigated. Scanning electron microscopy (SEM), x-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP) tests were carried out to analyze the effect of silver and chilled solidification on the corrosion performance of AZ91 alloy. The silver-containing samples showed better corrosion resistance, mainly due to its effect on the microstructure modification of the alloy by altering the morphology of the β-Mg17Al12phase. As a result, corrosion current density of silver-containing samples was lower than the original AZ91 Mg alloy down to 4 times. The corrosion rate of to the AZ91 alloy with 0.4 wt.% silver and pouring temperature of 750 °C was 0.256 mm.y-1. More uniform microstructure of the β phase due to the addition of silver could facilitate the uniform growth of corrosion products, which led to the lower corrosion rate of the AZ91 alloy.