Preparation And Properties Of Aluminum And Aluminum Based Alloy Coatings Electroplated From Organic Molten Salts

Electrodeposition of aluminum and aluminum alloy coatings onto Q235 steel from AlCl3-BPC and AlCl3-MEIC organic molten salts were carried out. The effect of parameters of electrodeposition on structure, thickness, surface morphology, adhesion force with matrix and corrosion resistance of aluminum coatings were determined and discussed. The results show that the electrodeposition of aluminum and aluminum alloy coatings onto Q235 steel from organic molten salts is feasible.The aluminum coating from AlCl3-BPC is smooth, compact, uniform and with large irregular particle or sheet form. The thickness of aluminum coatings is proportional to the current densities, time and temperature. With the increase of current density, the corrosion resistance of aluminum coatings rises first and then decreases; the grain size and the adhesion force with the matrix are reduced. With the increase of electroplating time and temperature, the grain size and corrosion resistance of the coatings goes up, but the adhesion force with the matrix is lowered. The addition of benzene improves the conductivity of plating solution and makes the aluminum coatings with greater thickness, finer grain size, higher corrosion resistance and lower adhesion force.Aluminum-manganese alloy and aluminum-manganese–molybdenum alloy coatings were electrodeposited by adding MnCl2 and MoCl5 into AlCl3-BPC organic molten salt. The results indicate that the pitting corrosion resistance of coatings is enhanced by the addition of Mn and Mo elements which exist in the form of solid solution. There is amorphous phase in the Al-Mn alloy coating when the content of Mn reaches a certain value. For Al-Mn alloy coating, the adhesion force is reverse to the current density and plating time. With the current density increasing, the thickness of aluminum coating rises firstly, then decreases to a minimum and afterwards rises again. As the increase of current density and plating time, the content of Mn and corrosion resistance of coating get higher to a maximum and then become lower. As for Al-Mn-Mo alloy coating, when the current density get larger, the thickness and adhesion force of the deposited coating have a little vary and the content of Mn presents a trend of rising firstly and then decreasing. But the content of Mo has no obvious change. The aluminum coating with a silvery white color from AlCl3-MEIC is composed of irregular particles. The thickness of aluminum coatings increases with the current density and plating time, and reduces with the temperature increasing. With the increasing of current density, their corrosion resistance decreases firstly, and then increases gradually. The adhesion force of coating with matrix is decreasing when the current density and plating time increase.