Among all the surface coatings of zinc and its alloys, zinc-nickel has a number of advantages that makes it the leader:
i) Greater resistance to corrosion: The presence of 12 to 16% Ni in its structure, allows it to acquire the gamma phase, which gives it greater resistance to corrosion in salt spray and in climatic cycles compared to other applications from Zn.
ii) High resistance to wear: The hardness of the coatings prevents them from being damaged in the coating process itself, as well as in subsequent manipulations such as packaging, selections, transport, assembly, etc.
Layer hardness of various coatings:
Zn: 100 HV
ZnFe: 150-200 HV
ZnNi: 500-550 HV
iii) Reduced white corrosion formation: White corrosion in the ZnNi coating appears much less bulky than in other Zn coatings
iv) Good stability at high temperatures: The ZnNi deposit is very stable at temperature, even keeping its properties at working temperature up to 200 ºC.
v) Low Hydrogen embrittlement: Due to the characteristics of the layer of the deposit formed, as well as those of the deposition process, ZnNi presents low Hydrogen embrittlement, as already indicated in standards with ISO 4042.
vi) Low corrosion by contact with Aluminum: Due to the difference in oxidation potentials of Zn and ZnNi, the latter has much less galvanic corrosion by contact with Al, which makes it a coating widely used in both the automotive and in other sectors.