Developing an empirical relationship to predict the corrosion rate of friction stir welded AZ61A magnesium alloy under salt fog environment

Magnesium (Mg) alloys shows the lowest density among other engineering metallic materials. As a consequence, this light alloy has a promising future. However, these alloys have great affinity for oxygen and other chemical oxidizing agents. The limitation of low corrosion resistance restricts their practical applications. Extruded Mg alloy plates of 6 mm thick of AZ61A grade were butt welded using friction stir welding (FSW) process. Corrosion behavior of the welds was evaluated by conducting salt fog test in NaCl solution at different chloride ion concentrations, pH value and spraying time. Also an attempt was made to develop an empirical relationship to predict the corrosion rate of friction stir welded AZ61A magnesium alloy. Three factors and a central composite design were used to minimize the number of experimental conditions. Response surface method was used to develop their relationship. The developed relationship can be effectively used to predict the corrosion rate of friction stir weld AZ61A magnesium alloy at 95% confidence level.

► Extruded AZ61A Mg alloy plates of 6 mm thick was butt welded using friction stir welding process.
► Corrosion behavior of the welds was evaluated by conducting salt fog test.
► An empirical relationship was developed to predict the corrosion rate.
► Response surface method was used to develop their relationship.
► The corrosion rate was higher in the acidic media.