Electroless nickel Ni/P (version 5)
N.B.: The information contained in this sheet comes from reliable sources. Nevertheless, it is provided without any guarantee, express or implied, of its accuracy.
Principle:
The process consists in immersing the part to be treated in a bath containing nickel salts and a reducing agent. The nickel ions will reduce to nickel metal and deposit on the substrate. The reducing agent is hypophosphite which produces a nickel/phosphorus alloy. The most remarkable characteristic is the regularity of the thicknesses.
The deposit is indeed capable of evenly coating parts with complex geometries including edges, corners and deep bores. Electroless nickel Ni/P also has a high hardness, especially after heat treatment resulting in Ni3P precipitation. However, the metallurgical characteristics of aluminum alloys rarely allow to exceed 130°C / 1h, which nevertheless allows to improve the adhesion, but without increasing the hardness.
ASPECT: matte to glossy
THICKNESS: 5 to 50 μm (> 200 μm for repair)
MICRODURITY: 450 to 550 Hv0.1
MORPHOLOGY: porous deposit for low thicknesses
WELDING: tin/lead solder
COLD RUNNESS:
- excellent on cast iron
- good on steel
- average on chrome and on itself CORROSION RESISTANCE:
- requires a minimum of 30 / 50 μm to be watertight (nickel is more noble than aluminum)
- good resistance to dilute non-oxidizing acids
- good resistance to strong bases
note: properties are determined by the phosphorus content of the deposit (low phosphorus, 6 to 8% and high phosphorus, 9 to 13%) which depends on the formulation of the bath used
SUBSTRATE:
All aluminum alloys.
APPLICATIONS :
Hardness, resistance to wear, friction and erosion.
Electrical conductivity.
Ability to make conductive, or even weldable, materials that are not.
Use as an undercoat for chrome, tin or precious metal deposits
Applications: automotive, connectors, electronics ...
SELECTION CRITERIA - LIMITATIONS :
Good electrical conductivity, hardness and wear resistance
The difference in potential between aluminium and nickel is >> 300 mV, hence the need for a tight deposit, i.e. thick and woundless, to avoid rapid corrosion of the aluminium in a humid environment.
Nickel is known to be a skin sensitizer, and prolonged direct contact can cause an allergy.
ENVIRONMENTAL IMPACT:
Regulation of the nickel content in water discharged by TS workshops. Note that there are formulations without lead or cadmium.
REFERENCE:
ISO 4527 : application, all sectors
ISO 4516: Vickers and Knoop microhardness measurement
ISO 9227-NSS : neutral salt spray test
EN 12 373-18 : Pitting corrosion rating system
FED.TEST METHOD STD.141C Method 6192-1: Abrasive wear resistance TABER method
Implementation
Main equipment (furnace, reactor, line, machine...)
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