Study On Electroplating Aluminum In Molten Salts And Its Properties

The electroplating aluminum on Q235 steel has been realized and obtained a certainty plating layer at 150℃ and 800℃ respectively in molten salts of AlCl3-NaCl-KCl and NaCl-KCl. The electroplating aluminum prescription of salts bath, the influence of technique parameters on the thickness of plating layer, composition and phase structure of plating, bonding situation, corrosion resistance as well as oxidation resistance has been systematically studied using optic microscope, scanning electronic microscope, X-ray diffract meter, the method of weightlessness in static state soaking at room temperature, and the oxidation method at high temperature.Result shows that the thickness of plating increases with the current density increasing and the duration electroplating time prolonging despite of low or high temperature. The electroplating of aluminum layer was forming in terms of nucleating and growing up and stratifying growth pattern of aluminum grain at low temperature. The appearance of aluminum layer was as flake-like at lower current density. While the appearance of aluminum layer was as spheroid-like at higher current density. At high temperature, the forming of plating layer is similar to the forming pattern of electroplating at low temperature. However, at low current density, the appearance of aluminum layer was as lump-like. At higher current density, the appearance of aluminum layer was as needle-like. At low temperature the plating layer was bonded mechanically with the substrate. Moreover, it was metallurgy bonded between plating layer and substrate at high temperature. The analysis of scanning electron microscope and X-ray diffraction shows that the structure of plating layer was single-phase aluminum not only at low temperature but also at high temperature. The result of weight losing method in static state soaking shows that thecorrosion resistant of plating on Q235 steel is superior to theABSTRACTnon-electroplating specimen. When the current density was7.895A/dm2 and the electroplating time were 60 minutes, the corrosion resistant of plating layer was 5 times as high as non-electroplating specimen in the 3%NaCl solution. The high temperature oxidation experiment shows that the high temperature oxidation resistant of plating layer on Q235 steel has been improved greatly. The more thickness of plating layer, the high temperature oxidation resistant of plating has been improved dramatically.