Corrosion behavior of pure Mg and AZ31 magnesium alloy

Abstract

Purpose of this article is to study corrosion behavior of pure magnesium and AZ31 magnesium alloy in electrolyte containing different concentrations of sodium chloride and pH. For this aim, different concentrations (3.5, 0.3 and 0.03 wt %) of NaCl salt has been utilized in immersion and potentiodynamic polarization tests. pH of electrolytes were fixed at 3, 6 and 11 in order to determine combined effects of acidity and chloride ion concentration on corrosion behavior. It was found out that in the case of AZ31 alloy similar to magnesium, corrosion rate is higher and open-circuit potential was more negative at higher chloride ion concentration in each pH, and also same trend is observed at lower pH for each chloride ion concentration in corrosion rate and open circuit potential. Indeed, solution pH value will have inverse relationship with alloy’s corrosion rate in that solution and by increasing pH, corrosion rate will be decreased. The impact of variations in chloride ion concentration is greater than the change in the solution pH. Corrosion behavior of the magnesium alloy is controlled through a slightly superficial protective layer. It is also expected that the corrosion rate obtained from immersion test to be higher than the one derived from polarization test.