Corrosion Protection of Mg-Alloys with Cold Sprayed Composite Coatings

Due to the demand for improved fuel economy as well as increased safety features, weight reduction is one of the major aims in the automotive industry. Future lightweight automotive components for the next car generation will probably use lots of magnesium alloy. These will form galvanic couples with other materials and may be induce phenomena accelerating the corrosion rate of automotive components. The paper objective was to evaluate the magnitude of galvanic corrosion between typical ferrous and magnesium alloys. The materials used were magnesium alloy AZ31B and low alloy steel. The relative performance of each cold sprayed corrosion preventive compounds (CPC) was assessed in combination with the materials under several different electrochemical and accelerated corrosion tests. Baseline data for the test materials with no CPC applied was also collected. CPC characteristics and properties are also included and discussed. Electrochemical studies on bare Mg/Steel couples validated accelerated corrosion but found that CPC cold sprayed coatings mitigate corrosion rates. Thus Mg/Fe interfaces with defect -free cold sprayed composite coatings can prevent buildup of corrosion products and reduce galvanic corrosion of automotive components.