OXIDATION OF ELECTROLESS Ni-B AND Ni-P COATINS IN AIR AT 800 TO 1000 degree C.

The oxidation of electroless Ni-B coatings in air at 800 to 1000 degree C has been determined by kinetic, X-ray diffraction, and microscopical methods. Some data have also been obtained on the oxidation of Ni-P coatings, the oxidation of nickel, and the effect of Na//2SO//4 on the oxidation process. All kinetics followed the parabolic oxidation law and the rate increased in the order spectrographically pure nickel, commercially pure nickel, Ni-B, and Ni-P, with the Ni-P oxidizing approximately 1000 times faster than the spectrographically pure nickel. Fine surface deposits of Na//2SO//4 greatly increases the oxidation rate of all materials except the Ni-P coatings which appear to be immune to hot-corrosion. The nature of the oxidation processes are discussed.