Nondestructive evaluation of an environmentally friendly conversion coating for magnesium alloys using an infrared proximity sensor and polarized light microscopy techniques

Document Type

Conference Proceeding

Publication Title

Magnesium Technology


Magnesium alloys have one of the highest specific strengths of all construction materials used. Although magnesium alloys provide additional desirable traits such as high damping capacity, reduced tool wear and lower melting temperatures for ease of recycling, they are also the most prone to corrosion when compared to all construction materials.1 Anti-corrosion coating systems allow the use of magnesium alloys in harsh environments, as in the case of the H-60 helicopter magnesium alloy gearbox housing. However, the conversion coating which forms the foundation of many of these coating systems employs chromium. In an effort to phase these harmful chromates out of the coating system and continue to use magnesium alloys, an environmentally friendly conversion coating has been developed. This paper shall present data acquired from an infrared proximity sensor which shows the difference between an environmentally friendly coated magnesium alloy ZE41A and uncoated ZE41A to establish a measure of quality control for the environmentally friendly coating. This paper shall also present data acquired using traditional polarized light microscopy techniques to determine the difference between a coated and uncoated magnesium alloy using mean gray value counting to achieve the same goal as the infrared sensor experiment.

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