The Corrosion Behavior of Mg5Y in Nominally Distilled Water

This paper studies the macro and micro corrosion of Mg5Y in nominally distilled water. The Y‐containing corrosion product film formed on the alloy surface provides some protection for the Mg matrix to the galvanic corrosion caused by Y‐containing second‐phase particles. In some cases, there is no corrosion of the matrix surrounding most of the second phase particles. However, about 2% of the second‐phase particles in the as‐cast Mg5Y causes micro‐galvanic corrosion, resulting in ‘bump’ or ‘volcano’ shaped corrosion product deposit. These ‘active particles’ cannot be significantly reduced by solution‐heat‐treatment. The Y‐containing corrosion product film on Mg5Y provides some protection for the matrix to the galvanic corrosion caused by Y‐containing second‐phase particles. Only 2% of the second‐phase particles can cause the galvanic corrosion in as‐cast Mg5Y, which cannot be reduced by solution‐heat‐treatment.