Electroless Nickel

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Electroless Nickel Mil Spec Thickness Comments
MIL-C-26074B
Similar to stainless steel in color. Plates uniformly in recesses and cavities (does not build up on edges). Corrosion resistance is good for coatings over .001” thickness. Electroless nickel is used extensively in salvage of mis-machines parts. Also, for inside dimensions and irregular shapes (where assembly tolerances need uniformity provided by “electroless” process).



Class 1
Class 2


Class 3


Grade A


Grade B

 Unless otherwise specified




.001”


.0005”



As coated.
Steel, copper, nickel, and cobalt base alloys. Heat treated after plating.

Aluminum alloys other than alloy 7075. Heat treated after plating.

Minimum thickness. For iron and aluminum based alloys.

Minimum tickness. For copper, nickel, and cobalt based alloys.


ASTM Designation: B 733

(Electroless) Nickel-Phosphorus Coatings

The performance of the autocatalytic nickel coating depends to a large extent on the surface finish of the article to be plated and how it was pretreated. Rough, non uniform surfaces require thicker coatings than smooth surfaces to achieve maximum corrosion resistance and minimum porosity

Table 1 Deposit Alloy Types
Type
 Phosphorus % wt.
I
 No Requirement for Phosphorus
II
 1 to 3
III
 2 to 4
IV
 5 to 9
V
 10 and above

Table 2 Service Conditions

Coating Thickness Requirements
Service Condition
Minimum Coating
Thickness Specification
µM
In.
SC0
 Minimum Thickness
0.1
 0.000004
SC1
 Light Service
5
 0.0002
SC2
 Mild Service
13
 0.0005
SC3
 Moderate Service
25
 0.001
SC4
 Severe Service
75
 0.003

4.3 Post Heat Treatment Class – The nickel-phosphorus coatings shall be classified by heat treatment after plating to increase coating adhesion and or hardness.
4.3.1 Class I – As deposited, no heat treatment.
4.3.2 Class 2 – Heat treatment at 260 to 400°C to produce a minimum hardness of 850 HK100.
4.3.3 Class 3 – Heat treatment at 280 to 200°C for 2 to 4 h to improve coating adhesion on steel and to provide for hydrogen embrittlement relief.
4.3.4 Class 4 – Heat treatment at 140 to 150°C for at least 1 h to improve coating adhesion for aluminum, non age-hardened aluminum alloys, copper, copper alloys and beryllium


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