PURPOSE: To provide a film having excellent corrosion resistance with minimum pin holes by a method wherein the film is Ni-plated using a plating solution in specific composition thereby minimizing the elution amount from the magnet surface while enhancing the bond properties onto the magnet.
CONSTITUTION: A plating solution in pH6-8 comprizing nickel sulfate 70g/1-200g/l, one or two kinds of ammonium citrate or sodium citrate 25-50g/l, boric acid 10g/l-30g/l, one or two kinds of ammonium chloride or sodium chloride 6g/l-10g/l, stress inhibitor 3g/l-5g/l is prepared. Next, the surface of the Fe-B-R base sintered magnet before Ni-plating step is cleaned up to be Ni-plated using the plating solution. Through these procedures, the elution amount of the sintered magnet during the plating step can be minimized while reinforcing the film brittleness peculier to neutral, alkalic plating solution thereby enabling the Ni-plated film having excellent bond properties as the sintered magnet and the corrosion resistance with minimum pin holes to be provided.
MIYAO YUKIMITSU
SUZUKI MASAKO
SAIGO TSUNEKAZU
YAMASHITA MICHIO
