Improvement of corrosion resistance of AZ61 magnesium alloy / Zvýšení korozní odolnosti hořčíkové slitiny AZ61

This paper deals with investigation of corrosion resistanceof extruded AZ61 magnesium alloy. A phosphate-permanganateconversion coating was prepared on the surface ofexperimental alloy to improve corrosion resistance. This conversioncoating was prepared as an alternative to the chromatingprocess which showed great results in the case of magnesiumalloys. Nevertheless, the use of chromates is limited by theenvironmental regulations in Europe. The corrosion resistanceof extruded AZ61 magnesium alloy with or without conversioncoating was tested by means of an immersion test. The sampleswere immersed in sodium chloride solution (3.5%) with immersiontimes of 1, 8, 48 and 168 hours. The weight losses weremeasured using an analytical balance (d = 0.1 mg) and expressedas corrosion rate in [mm.year^-1]. Microstructure, surfacemorphology of conversion coating and corrosion attack wereobserved by means of light and scanning electron microscope.