|About this Abstract
||2012 TMS Annual Meeting & Exhibition
||Magnesium Technology 2012
||The Influence of Galvanic Current on Cerium-Based Conversion Coatings on Mg, Al, and Galvanized Steel Couples
||Surender Maddela, Matthew J O'Keefe, Yar-Ming Wang
|On-Site Speaker (Planned)
The influence of galvanic current on cerium-based conversion coatings (CeCCs) for magnesium (AZ91, AZ31), aluminum (6016), and electro-galvanized steel (EGS) couples has been studied using zero resistance ammeter (ZRA) measurements in prohesion solution. The galvanic current measured between magnesium-aluminum, magnesium-galvanized steel, and aluminum-galvanized steel couples correlated with significant changes in coating morphology and deposition rate. The ZRA galvanic currents (mA) were 0.02 for 6016-EGS, 0.38 for AZ91-EGS, 0.72 for AZ91-6016, 1.08 for AZ31-EGS, and 1.08 for AZ31-6016 couples. The corrosion performance of the coated couples was evaluated by ASTM B117 neutral salt spray testing and electrochemical polarization measurements. Cerium conversion coated couples performed better in salt spray testing compared to uncoated couples. The correlation of galvanic current, cerium deposition, and corrosion performance will be discussed.
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