Corrosion resistance of AZ31 alloy after plastic working in NaCl solutions

Purpose: The purpose of the study was to assess corrosion resistance of magnesium alloy AZ31 (Mg-Al-Zn alloy) after plastic working in NaCl solutions. It presents currently applied methods of magnesium alloys plastic working. Basic groups of magnesium alloys that are used for plastic working have been discussed. Design/methodology/approach: Corrosion tests of AZ31 alloy were carried out in solution with concentration of 0.01-2 M NaCl with application of the system for electrochemical tests VoltaLab®PGP201. Resistance to electrochemical corrosion was evaluated on the ground of registered anodic polarisation curves by means of potentiodynamic method. Immersion tests were carried out in NaCl solutions in the time of 1-5 days. Scanning microscopy enabled to present microstructure of AZ31 after immersion tests. Findings: Results of all carried out tests explicitly prove deterioration of corrosion properties of magnesium alloy AZ31 with the increase in molar concentration of NaCl solution. Practical implications: It was determined that irrespective of molar concentration of NaCl solution pitting corrosion was found in the tested alloy. It proves that application of protective coating on elements made of the tested alloy is necessary. Originality/value: Literature gives the results of corrosion tests with reference to cast alloy AZ31. Tests of corrosion resistance of hot rolled AZ31 in chloride solutions have been made for the first time.