| A kinetic study on the electrodeposition of Ni-P alloys onto a steel has been performed using a rotating disk geometry. The effect of potential and temperature on the deposition rate of Ni and P was higher than the stirring speed of the solution. The calculated activation energies of Ni and P in the higher temperature ranges between 66 ℃ and 86℃ were about 8 ㎉/mole and 9 ㎉/mole respectively, however, in the lower temperature ranges between 46℃ and 60℃ were about 29 ㎉/mole and 30 ㎉/mole, respectively. Accordingly, the reaction rate of Ni-P codeposition seems to be controlled partly by electrochemical reaction and partly by mass transport, namely mixed controlled. As the applied potential increased, the ratio of P in the deposit was decreased, however, the stirring speed and temperature had little effect on the ratio of P in the deposit The ratio of Ni in the deposit was increased, however, that of P was decreased as the increase of difference between bulk concentration and surface concentration(C_h-C_s) of the electrolytic solution in the experimental range of potential, temperature and stirring speed. The as-deposited Ni-P was amorphous but the deposit was crystallized to Ni₃P after heat treatment for 4 hours at 400℃. |
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