Effect of pH values, chloride ion concentration and exposure time on pitting corrosion rates of friction stir welded AZ61A magnesium alloy in sodium chloride solution using surface response methodology

Abstract

Extruded AZ61A Mg alloy plates of 6 mm thickness were friction stir welded. The effect of pH values, chloride ion concentration and exposure time on the pitting corrosion rate of magnesium alloy welds was investigated in NaCl solution using potentiodynamic polarisation tests. In addition, an attempt was made to develop an empirical relationship to predict the pitting corrosion rate of Mg alloy welds by incorporating the effect of pH values, chloride ion concentration and exposure time using response surface methodology. Microstructural characterisation of the corroded specimens was analysed under light optical microscopy. The corrosion products were analysed using SEM and X-ray diffraction.

Keywords:

• Magnesium
• Polarisation
• SEM
• Welding
• Pitting corrosion

The authors would like to thank the Centre for Materials Joining & Research (CEMAJOR), Department of Manufacturing Engineering, Annamalai University, Annamalai Nagar, for extending the facilities of the Materials Joining Laboratory and Corrosion Testing Laboratory to carry out this investigation.