Corrosion resistance of electroless nickel alloys

The most important significance in electroless deposition of metals have Ni-P coatings. They are characterized by excellent corrosion and wear resistance. Introduction of additional metal improves technical parameters of Ni-P. Various types of alloys are obtained in this way, for instance Ni-Co-P, Ni-Cu-P, Ni-W-P, Ni-Fe-P, Ni-Re-P, Ni-Mo-P, Ni-Zn-P, Ni-Sn-P. According to the literature data it is known that the Ni-Cu-P layers are thermal- and corrosion-resistant, Ni-Co-P as well as Ni-Fe-P have magnetic properties. Besides, Ni-Mo-P have great hardness and perfect resistance to high temperature. This type of alloy is used as thermalproof resistors. Ni-Sn-P coatings could be applied for printed circuits and as decorative layers. Content of additional element in coating can achieve from few to several weight percent and depends on metal concentration in the bath and also of process conditions. This work gives a short review of the published data on the corrosion behavior of nickel based alloys (deposited by electroless method) in the recent years. The market analysis concerning the industrial application of such coatings is showed as well.