Characterization of Ni-P electroless coatings deposited on internal surfaces

Electroless nickel deposition with sodium hypophosphite forms a Ni-P amorphous deposit with 4 to 12% (in mass) P content. The corrosion resistance of this kind of coating depends on phosphorus content, and the phosphorus content depends on the operational conditions of the batch. Usually, this coatings are deposited by total immersion of the part, but when it is wished to coat only internal surfaces (as in tubes), it is necessary to recirculate the electroless nickel solution through the tube, in order to prevent the external surface from coating. This work shows the results of the characterization of electroless coatings deposited to protect. This work shows the results of the can say that it is possible to coat internal surfaces by this technique, and that the flow regimen does not affect the coating phosphorus content; on the other hand, the deposition rate and morphological characteristics are affected. 9 refs