Processes

Chemical nickel plating

With the chemical nickel plating surface treatment we create a uniform nickel coating with low, medium or high phosphorus content on metal components made of aluminium, copper, iron alloys and on sintered metals. In contrast to electrolytic nickel plating, chemical nickel plating evenly coats parts with complex shapes, holes or undercuts with a uniformity of ±1 μm.

Chemical nickel-plating gives the surfaces a micro-hardness of 450 to 1,100 HV and a resistance of up to 1,000 hours in salt spray.

The electroless nickel coating is purely functional, but to meet the demands of its partners, Alfatech can give it an aesthetic value. Chemical nickel plating may be followed by dehydrogenation or heat treatments to stabilise the deposit and increase its hardness.

COATING FEATURES

  • Thickness from 4 to 120 μm
  • Coating uniformity (±1 μm)
  • Guaranteed tolerance ±2 μm
  • 1000 h NSS
  • Non-magnetic deposit
  • Frame treatment
  • Rotary barrel treatment

TREATABLE WEIGHTS AND MEASURES

  • • Minimum dimensions: a few millimetres
  • Maximum cylinder dimensions: 950 mm – ø 450 mm – weight 450 kg
  • Maximum dimensions of parallelepipeds: 950x450x850 mm – weight 450 kg

TECHNICAL DETAILS

Nickel
Low phosphorus
Nichel
Medium Phosphorus
Nichel
High phosphorus
% phosphorus 1-3 5-9 10-13
Obtainable thicknesses (tolerance ±2 µm): 4-120 µm 4-120 µm 4-120 µm
Coating uniformity: ±1 μm ±1 μm ±1 μm
Knoop hardness as is (HK100) 725-800 500-600 450-500
Hardness after T.T. Knoop (HK100) 900-1100 850-1000 850-950
Magnetic properties as is Magnetic From slightly magnetic to magnetic Non-magnetic
Melting range (°C) 1250-1360 1100-1300 880-900
Brass – 25 μm resistance
at hour neutral salt spray
≥ 300 ≥ 1000 ≥ 1000
Carbon steel – 25 μm resistance
to neutral salt spray
≥ 96 hours ≥ 180 hours ≥ 240 hours

Nickel Low phosphorus

% phosphorus: 1-3
Obtainable thicknesses (tolerance ±2 µm): 4-120 μm
Coating uniformity: ±1 μm
Knoop hardness as is (HK100): 725-800
Hardness after T.T. Knoop (HK100): 900-1100
Magnetic properties as is: Magnetic
Melting range (°C): 1250-1360
Brass – 25 μm resistance at hour neutral salt spray: ≥ 300
Carbon steel – 25 μm resistance to neutral salt spray hours: ≥ 96 hours

Nickel Medium Phosphorus

% phosphorus: 5-9
Obtainable thicknesses (tolerance ±2 µm): 4-120 μm
Coating uniformity: ±1 μm
Knoop hardness as is (HK100): 500-600
Hardness after T.T. Knoop (HK100): 850-1000
Magnetic properties as is: From slightly magnetic to magnetic
Melting range (°C): 1100-1300
Brass – 25 μm resistance at hour neutral salt spray: ≥ 1000
Carbon steel – 25 μm resistance hours neutral salt spray: ≥ 180 hours

Nickel High phosphorus

% phosphorus: 110-13
Obtainable thicknesses (tolerance ±2 µm): 4-120 μm
Coating uniformity: ±1 μm
Knoop hardness as is (HK100): 450-500
Hardness after T.T. Knoop (HK100): 850-950
Magnetic properties as is: Non-magnetic
Melting range (°C): 880-900
Brass – 25 μm resistance at hour neutral salt spray: ≥ 1000
Carbon steel – 25 μm resistance hours neutral salt spray: ≥ 240 hours

SECTORS OF APPLICATION

  • Food sector (pipes, shafts, various valve bodies and taps, beverage and beer taps, die, boilers, tubes, nozzles, coffee heat exchangers, fittings and spirals for meat grinders, rotors and valves for dosing powders and flours, pinions and prt. for washing systems and selection of fruits and vegetables)
  • Pharmaceutical sector (plates, folders, strips, sealing bars, dispensers for filling machines (solids/liquids/creams), packing machines, thermoforming machines, blister machines, capsuling machines)
  • Aeronautical/Aerospace/Naval (cover, plates, bracket, spacer, support, frame)
  • Automotive sector (cores and canisters for LPG/CNG injector bodies, pins and linkages for wipers, injectors, heads, cylinders, pistons)
  • Motorcycle sector (pulleys, clutch bells/fixed and mobile hubs, shock absorbers for motorbikes and quadricycles)
  • Electronics/Telecommunications sector (relay/breaker components, shafts, drive shafts, pins)
  • Hydraulics and pneumatics (pins for cranes/hoists, valve bodies/pistons and rods for hand pumps, gears, pistons, cylinders)
  • Petrochemical/Oil & Gas/Nuclear sector (spheres, bodies, rods, flanges, spacers, housings)
  • Textile sector (Clamps and wire guides, washers, pulleys, sliding tables, taping machines for fabric processing, shrouds, plates, sinker rings, covers, cylinders)
  • Medical sector (components for dental micro-tools including pins/nails/fittings and tube extensions, etc.; parts for clinic furniture such as headrest rods, footrest rods, connecting rods, etc.)
  • Packaging sector (various components of automatic packaging machines for packaging foodstuffs, detergents, cigarettes, etc.)
  • Military sector (rings, covers, supports, tails, shutters, drums etc. for plastic/glass material (internal body, external body, layer)
  • Weapons sector (chokes)
  • Wind sector (blade movement chains)
  • Chemical sector (moulds)
  • Railway sector (rails)
  • Telecommunications sector
  • General Mechanical sector (metalworking)
  • Electronic Small Parts Sector

Download

In this section you can download the PDF for the specific process.

FAQ

How many types of chemical nickel plating are there?

To date, about 40 different types of nickel chemicals are known, and they are commonly divided into acid and alkaline baths. Alkaline baths are defined as baths with pH > 7.00 and acid baths as pH < 7.00. More generally, they are subdivided by the amount of phosphorus they contain, into low, medium and high phosphorus electroless nickel plating.

What is the best chemical nickel plating?

There is no nickel plating that is better than others each of these families differs according to the scope of application of the part.

Electrolytic Nickel Plating Vs Chemical Nickel Plating

Chemical nickel plating is a chemical reaction, which takes place thanks to a precise product formulation and energy supplied in the form of heat.
The deposition process occurs by converting the nickel in the solution into metallic nickel; this reaction occurs directly on the surface of the metal which is coated in the process.
No current is used in the plating tank as this is a chemical process.
This prevents the tip effect, typical of electrolytic nickel, from occurring (increased thickness on part edges and ends, resulting in low thickness or lack of undercut and cavity coverage). The result is a uniform, controlled and homogeneous deposit across all surface areas in contact with the solution.

Do stresses in steels affect chemical nickel plating?

Yes, it is essential to carry out stress-relieving treatments. The main problems that could interfere with chemical nickel plating are related to the presence of oxides on the surface of steels. The main example is calamine, which prevents chemical nickel plating from taking place.
It is also essential to carry out mechanical surface cleaning, such as brushing or sandblasting. Stress in the material may cause the material to fracture or even compromise the adhesion of the nickel-plating process. Any material or coating subjected to stress induces tension and therefore cracks. Cracks are the first cause that starts a corrosive process.

I have carried out a stress-relieving process on the steel, so can I expect a satisfactory outcome to chemical nickel plating?

Normally the answer is yes, you need to pay attention to the possible layer of calamine that may form on the surface of the piece (see answer to FAQ “Do stresses in steels affect chemical nickel plating?”) or, if the heat treatment was carried out in a controlled atmosphere, check that the steel has not reached a degree of passivation such as to discourage surface treatment processes. If it cannot be controlled, sandblasting treatment is recommended beforehand.

I have a chrome-plated steel, can I chemically nickel-plate it?

For steels with a high carbon content, sandblasting treatment would be advisable before chemical nickel plating.

I have a steel with a high carbon content, would it be possible to carry out chemical nickel plating?

For steels with a high carbon content, sandblasting treatment would be advisable before chemical nickel plating.

Do a chemically heat-treated nickel-plated article and an untreated one have the same corrosion resistance?

No, a chemically nickel-plated and dehydrogenated part has a higher corrosion resistance than a heat-treated component.

Why do heat-treated parts after chemical nickel plating vary in colour?

During the heat treatment phase at maximum hardness, the parts are heated to the maximum temperature of approximately 315-380°C for a processing time of 4 to 12 hours. In this phase the electroless nickel deposit alters its physical state, the deposit increases in hardness, reaching a nanocrystalline conformation (the maximum hardness attainable for a high phosphorus electroless nickel deposit is 1100 HV).
If the furnace used for the treatment is not a vacuum furnace, the air in contact with the coating during the cooling phase gives rise to different colours called interference colours. The colouring can range from golden yellow to purple, but does not impact any functionality the coating; on the contrary, it ensures that maximum hardness is achieved. If unwanted, it can be removed by mechanical surface cleaning.

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