The conversion coating of magnesium alloy by immersion in NaOH solution containing carbonate ion

초록

Abstract. Magnesium alloys are highly considered as interesting materials in various industries such as transport, aerospace and portable device due to its low density comparing with other metals. However, magnesium is so vulnerable to corrosion that improvement of corrosion resistance is necessary to be commercialized. There are various methods to enhance corrosion resistance of magnesium such as anodizing, conversion coating, electrochemical plating, electrolytic plasma oxidation, and so on. Among these treatment, conversion coatings have been widely applied to magnesium alloys because of simplicity in operation and excellent adhesive property. In this study, conversion coating films on the surface of AZ31 was fabricated by immersing the alloy in a 0.5 M NaOH solution saturated with CO2 gas. Immersing treatments were conducted with various immersion times at room temperature. Corrosion test was conducted to evaluate the enhancement of corrosion resistance using 5 wt. % NaCl solution, and physical properties were examined by scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS).