A Spot Test for Mg2+ to Characterize Magnesium Corrosion

ABSTRACT Magnesium alloys are often found on cultural heritage materials since their properties, including high strength and light weight, make them ideal for structural industrial applications. However, they are also highly reactive and prone to corrosion. Corrosion often presents as a white powder that can be easily mistaken for polish residue or other accretions when less severe. Manufacturers typically combat this corrosion risk with protective paint or conversion coatings, which can make it difficult to recognize magnesium alloys. The identification of magnesium alloys often relies on connoisseurship and knowledge of typical corrosion, coatings, or surface finishes, which can be difficult for those encountering the material for the first time or in nonspecialized collections. Identification through analytical means such as XRF, if available, is also complicated by magnesium's low atomic mass. As correct alloy identification is most important when there is corrosion that requires treatment, this note presents a simple microchemical spot test for the presence of the magnesium ion that can be used to confirm magnesium corrosion, and thus characterize the alloy and help determine the priority and type of treatment. This small-scale, wet chemistry test relies on relatively common and inexpensive reagents, making it widely accessible.