Electroless deposition and some properties of Ni–Cu–P and Ni–Sn–P coatings |
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Authors: | J Georgieva S Armyanov |
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Institution: | (1) Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Science, Acad.G.Bonchev str., Bld. 11, 1113 Sofia, Bulgaria |
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Abstract: | In this review, a summary of our published results, completed with new unpublished data are considered together with some
of other authors’ publications, making an attempt to reveal the mechanism of the third element co-deposition in electroless
Ni–P plating and to define its influence on the ternary coatings’ properties. A model explaining the triple role of Cu added
to the solution for electroless (EL) Ni–P plating is described: as a stabilizer Cu(I)]; as an accelerator; and as a stability-affecting
agent, forming a dispersed solid phase in the solution. The disproportionation reaction of Cu(I) has been taken into account.
A planned experiment was performed using full-effect factorial design with two levels of three process variables, and the
response surfaces were constructed. The interaction between the factors was revealed. The results are in harmony with the
aforementioned model. In low-tin Ni–Sn–P coatings, the alloy components are uniformly distributed both on the surface and
through the thickness. In contrast, high-tin coatings exhibit three-dimensional areas enriched in Sn and impoverished in Ni
and P. As the reason for their formation, the disproportionation reaction of Sn(II) is suggested, supposed to be locally predominant
over the hypophosphite oxidation. EL deposition of pure Sn onto Ni–Sn–P substrates is shown. The inclusion of Cu or Sn in
EL Ni–P increases the thermal stability of amorphous state, ensures the preservation of a paramagnetic behavior and improves
the corrosion resistance.
Dedicated to the 70th birthday of Professor A. Vaskelis. |
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Keywords: | Electroless Ni– Cu– P Electroless Ni– Sn– P Ternary alloys Thermal stability Disproportionation |
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