CHEMICAL NICKEL

Chemical Nickel – Properties

The surface properties are almost independent of the base material. The layer follows the surface geometry. Proper thermal after-treatment can increase the hardness and wear resistance.

Low P Nickel is relatively hard and magnetic.
Middle P Nickel is less hard, but gives reasonable corrosion protection, and as a result is applied most often. This layer shows weak magnetic properties.
High P Nickel is very corrosion resistant, and not magnetic

Chemical Nickel - Process

Chemical Ni can be deposited on;

steel and stainless steel
cast iron and cast steel
copper and copper alloys, both on extruded, cast and heat pressed parts
aluminium and aluminium alloys, both on injection moulded, cast and extruded parts
zinc injection moulded parts
plastics (among others ABS and polycarbonate)

Process characteristics

Chemical nickel is deposited in an aqueous solution of a nickel salt and a reducing agent at 85 to 95 °C. On plastics the chemistry is adjusted to a working temperature 60 to 75 °C.
We discriminate between

Ni containing 2 to 5% P (low)
Ni containing 6 to 9% P (medium)
Ni containing 10 to 14% P (high)

Composite layers with PTFE (Teflon), silicon carbide (SiC) and diamond particles are also deposited.

Pre-treatment

Mechanical pre-treatment for removing an oxide layer or to provide a desired final appearance may involve polishing, glass or sand blasting.
Pre-treatment depends on the type of base material. The products are always (electro) chemically cleaned and activated before deposition.

Layer deposition
This takes place over the entire surface. Surface roughness is determined by the base material. Thick layers could have a higher surface roughness. Partial deposition is possible (by covering part of the surface).

There is uniform covering over edges, through holes can be coated if the plating solution can be continuously refreshed. Layer thickness up to 200 µm is possible.
A thickness of 2 to 50 µm is usual on plastics up to ± 1.5µm.
Deposition rate is 8 to18µm/h.
Adhesion strength on steel and copper is 345 to 441 Mpa; on aluminium 103 to 241 MPa.

After-treatment

Thermal after-treatment (increase of hardness and wear resistance) is carried out at a temperature of 200 °C to 400 °C for 10 to 24 hours. For reduction of hydrogen brittleness annealing up to 240 °C may be required, dependent on the alloy composition of the steel substrate.

Advantages and disadvantages

Advantages;

Dimensional stability of the product (no edge building, and homogeneous thickness distribution)
The coating can be applied onto almost any material, designers have many options
Good corrosion resistance
Good resistance to abrasive wear.

Limitations;

low ductility of the layer
wear resistance is somewhat lower than that of hard chrome
some limitations to the geometry of the part to be coated
less uniform growth in through holes
maximum temperature during use (with constant functional properties of the layer) is around 320°C.

Costs
Costs are dependent on pre- and after-treatment, layer thickness and additional requirements

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Figure 1 to 4;

Chemical Nickel – Application

Chemical nickel is often applied on parts with a complex geometry. Exact dimensions can be attained by tuning the uniform layer thickness.

Applications;
Machines and Equipment; protection against wear and corrosion
Automobiles: Parts in carburettors, injection systems, and the ABS system. The aim is always corrosion and wear protection, and thermal conductivity.
Offshore: Thick layers for corrosion protection in (sea) water environment
Chemical industry: Process parts, reactor vessels, etc. for chemical resistance
Aerospace: Connection between solar panels and satellite. Corrosion resistance and high strength.
Electronics: EM shielding and solderability
Moulds: As top layer or intermediate layer for a PVD (e.g. DLC) coating. As an intermediate layer the function is to ‘bridge’ the hardness, and increase adhesion.

Chemical copper

Chemical gold