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Magnesium alloys are not corrosion resistant in many applications and they require coating protection. In this study, we developed an electroless E-coating technique for magnesium alloys and discussed a cathodic E-coating deposition mechanism for the electroless E-coating process. This coating can be formed within a few seconds by dipping a magnesium alloy (i.e., AZ91D) in an E-coat bath without applying a current or voltage. The deposited electroless coat can offer good protection to the AZ91D magnesium alloy in 5 wt% NaCl corrosive solution as well as in a phosphating bath. The most interesting finding is that the electroless coating is not sensitive to local damage. No preferential corrosion attack occurred along the scratches made on the coating.

A fastener finish quality monitor based on electrochemical impedance spectroscopy (EIS) has been successfully demonstrated on coated steel fasteners. The coating qualities can be assessed by comparing the measured spectrum with stored spectra of known samples, or by determining values of the coating-specific parameters extracted from the spectrum. Three areas of applications have been identified: (1). Quality control in the plant, (2). Coating process development, and (3). Accelerated corrosion evaluation.