ふっ化物処理を施した種々のマグネシウム合金の表面層組織と耐食性 Microstructures and corrosion resistance of surface layers formed on fluoride-treated magnesium alloys
A fluoride-treatment has been applied to various magnesium alloys, such as 3N-Mg, AZ31, AZ61, AZ91E and Ca-added AM60 alloys. The specimens of the alloys are dipped into molten NaBF<sub>4</sub> at 673 to 723 K for 0.3 to 86.4 ks. Surfaces of the specimens were successfully coated with surface layer by the treatment. Diffraction measurement in the synchrotron radiation facility SPring-8, BL-24XU (Hyogo prefecture beam line) showed that the surface layer was composed of NaMgF<sub>3</sub> and MgF<sub>2</sub> phases. The surface fluoride layer exhibits a superior corrosion resistance even in an immersion test using a 1% HNO<sub>3</sub> solution, filiform-like corrosion was suppressed for 1 to 3 ks in the solution depending on the alloy. Aluminum contents in the substrate alloys would affect the corrosion resistance by changing the microstructures in the fluoride layer.
軽金属 57(2), 57-61, 2007-02-28
The Japan Institute of Light Metals