Evaluation of electroless nickel surface treatment for iron powder used in MR fluids

Iron powders, used in magnetorheological (MR) fluids, were coated with nickel by electroless deposition. The ability of the coating to reduce the oxidation rate of the iron powder was evaluated by thermogravimetric analysis (TGA). Nickel metal appears to be very effective in reducing oxidation of the iron as indicated by the TGA results. However, the electroless treatment process also produces an undesirable decrease in both the saturation magnetization and the density of the iron powder. There is also a significant material handling difficulty as the treatment is conducted in a large volume aqueous suspension at elevated temperature.