The invention relates to a method for electrodepositing a nanocrystalline
nickel-
cobalt alloy by double-pulse. The method for electrodepositing the nanocrystalline
nickel-
cobalt alloy by double-pulse is characterized by comprising the following
processing steps: in a plating solution with a pH value of 5-6, a
nickel ion concentration of 0.68-0.95 mol / L and a
cobalt ion concentration of 1.9*10<-2>to 3.8*10<-2> mol / L, taking a soluble
nickel plate after the soluble
nickel plate is subjected to surface treating as a
anode, taking an iron sheet after the iron sheet is subjected to surface treating as a
cathode and
electroplating a nanocrystalline nickel-
cobalt alloy layer by using double-pulse electrodepositing technology, wherein the time for electrodepositing is 15-20 min, the positive-going
pulse current density is 1.0-2.0 A / dm<2>, the positive-going duty ratio is 60-80%, the working time of the positive-going pulse is 50-100 ms and the positive-going cycle is 40-60 ms; and the negative-going
pulse current density is 0.1-0.2 A / dm<2>, the negative-going duty ratio is 60-80%, the working time of the negative-going pulse is 10-20 ms, the negative-going cycle is 1-2 ms and the workingtime of the positive-going pulse is 5-10 times of that of the negative-going pulse. The nickel-
cobalt alloy coating prepared by the method has the advantages of
smooth surface, compact structure, fine and even
crystal, good smoothness, no crack and excellent
corrosion resistance.