CobaltMolybdenumPhosphorus Alloys: Electroplating and Corrosion Properties

V. Kublanovsky^a, O. Bersirova^a, Yu. Yapontseva^a, H. Cesiulis^b, and E. Podlaha-Murphy^c

^a Vernadskii Institute of General and Inorganic Chemistry, Ukrainian National Academy of Sciences,
pr. Akad. Palladin 32/34, Kiev-142, 03680, Ukraine

^b Vilnius University, Naugarduko 24, Vilnius, LT-03325 Lithuania

^c Northeastern University, Boston, MA, 021156 United States

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Received June 25, 2008

Abstract — The relation between the composition, morphology, and corrosion resistance of the electrolytic oMoP coatings plated at various current densities from citrate baths containing ammonia or hydrazine and various amounts of sodium hypophosphite is studied. Phosphorus was included in the coatings as a result of the electrochemical reduction of hypophosphite ions. Ternary Co–Mo–P alloys containing up to 26 at % Mo and p to 3 at % P were electroplated. Coatings of the highest quality were obtained from a bath containing hydrazine admixture at a temperature of 50°C. Corrosion resistance of CoMoP coatings increases with an increase in the Mo content and a certain decrease in the phosphorus amount in the deposit. The best protective properties were demonstrated by coatings obtained at higher concentrations of sodium hypophosphite and high deposition current densities when CoMoP alloys containing 23 2 at % Mo and up to 1.5 at % P were formed.