Influence of Conversion Coating Conditions with Rare Earth Elements on Corrosion Resistance of Mg alloys

摘要

Influence of the conversion coating with some rare-earth elements, such as La, Y, Sm, Nd and Ce, on corrosion resistance of Mg alloy has been studied. Effect of pretreatment, such as alkaline degrease, acid pickling and surface activation, has been also investigated. The surface of Mg alloy was covered with the so-called dry mad structure by the coating. The coating layer was a thin oxide film containing Mg, Al and rare earth element. F and P were detected in the coating with the pretreatment in addition. The corrosion resistance of Mg alloy against salt water was significantly improved by the conversion coating by immersion in the solution including both Mg(NO_3)_2 and rare earth nitrate. The corrosion resistance was improved by applying the pretreatment, further.