Sacrificial Cathodic Protection of Mg Alloy AZ31B by an Mg–5Sn Surface Alloy
A solid solution Mg–5Sn alloy is evaluated as a sacrificial anode for the cathodic protection of AZ31B. Uncoupled Mg–5Sn is shown to have superior barrier properties and reduced cathodic kinetics relative to AZ31B. The performance as a sacrificial anode was studied in situ with global and local measurements of galvanic coupling between the Mg–5Sn alloy and AZ31B when immersed in 0.6-M aqueous NaCl solution. The scanning vibrating electrode technique (SVET) was utilized to map the local current density distributions across the interface of the galvanic couple. Undesirable polarity reversal was observed during the initial 10 h of immersion, after which protection was offered. A self-corrosion rate of 52% was observed.
KeywordsMagnesium Cathodic protection AZ31B SVET
We gratefully acknowledge the US Air Force Academy under agreement number FA7000-12-2-0017 as part of Corrosion University Pilot Program under the direction of Mr. Daniel Dunmire and by the National Science Foundation under NSF DMR#1309999 as well as the Army Research Office under agreement number W911NF-14-2-0005. The US Government is authorized to reproduce and distribute reprints for government purposes notwithstanding any copyright notation thereon. The views and conclusions contained are those of the authors and should not be interpreted as necessarily representing the official policies or endorsement of the US Air Force Academy or the US Government. We also wish to thank Gregory Vavoso and Tony Nguyen for developing data processing software to assist with this study.
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