A hydrogen collecting and electrochemical synchronous measurement for studying galvanic corrosion behavior of AZ91D magnesium alloy

Purpose This research aims to provide a reliable method for actual galvanic corrosion rate test of magnesium (Mg) alloys coupled with other metals. Design/methodology/approach A die-cast AZ91D magnesium alloy was connected with pure Zn and Fe, and forming AZ91D-Zn and AZ91D-Fe couples. Hydrogen collecting and electrochemical synchronous measurement was conducted on these galvanic couples in 5% NaCl solution. Scanning vibrating electrode technique was used to measure the galvanic current distribution of AZ91D-Zn and AZ91D-Fe couples, which further proved the test results. Findings The results show that AZ91D-Zn couple exhibits quite weak galvanic corrosion and no negative difference effect (NDE) occurs, while there is strong galvanic corrosion and remarkable NDE on AZ91D-Fe couple. Originality/value A new developed method called hydrogen collecting and electrochemical synchronous measurement was established for the galvanic corrosion rate calculation of Mg and its alloys. By using this method, the real corrosion rate of Mg alloys in a galvanic couple can be obtained, and the NDE on the surface of Mg alloys can be quantitatively characterized.