Electroless Nickel-Phosphorus coatings have had a lot of interest in various industries due to
outstanding characteristics. Some of the highlighted characteristics of electroless Ni-P coatings are
superior corrosion and wear resistance. But the effectiveness of electroless Ni-P coating in resisting
cavitation damage is not studied so well and is not so clear. In the present investigation, electroless
Ni-P coatings were prepared at various conditions including the type of bath, heat treatment
temperature and plating solutions composition. The properties of electroless Ni-P coatings were
characterized using X-ray diffraction technique (XRD), energy dispersive X- ray (EDX) optical
microscope, and microhardness tester. The cavitation erosion tests were carried out to study the
effect bath type, heat treatment temperature and plating solutions composition on the deposit
coatings.
The XRD results indicate that the as-deposit had crystalline structure for alkaline bath and
amorphous structure for acid bath. Heat treatment of the coatings produced mixture of
polycrystalline phases. The thickness of deposit films depend on the bath type and concentration
and were the least for alkaline baths. Maximum hardness of heat treated samples was found to
depend on the solution composition and occurs at temperature 300 °C and 400°C.
The highest erosion resistance of the coatings was observed for the heat treated deposits at
temperature of 650 °C, and comes to the fore the coatings formed in alkaline baths followed by that
formed in acid baths. The best erosion resistance for deposits formed in alkaline baths is attributed
to the small thickness and crystalline structure. The results showed also that the cavitation erosion
resistance is independent on surface hardness.