About Electroless Nickel Plating: Chemical Reduction Coating Process
Electroless Nickel describes plating of a Nickel/Phosphorus coating onto a suitable substrate by chemical reduction. Unlike electroplated coatings, electroless nickel is an auto catalytic process where the coating is deposited onto a part’s surface by reducing nickel ions to metallic nickel with sodium hypo-phosphite. This chemical process avoids many of the problems associated with most metallic coatings and provides deposits with many unique characteristics.
As with all our coating and plating processes, we are capable of servicing a wide variety of part size ranges, up to 150 inches in diameter. This includes barrel plating as well as rack/wiring with or without masking.
Why should one utilize electroless nickel?
Properties of Electroless Nickel (EN)
Electroless Nickel coatings are uniform, hard, relatively brittle, lubrious, easily solderable, and highly corrosion resistant.
Processes of Electroless Nickel (EN)
► MEDIUM PHOSPHORUS: 6-9% (WEIGHT %) CONTENT
This is the most common electroless nickel process. Steel parts plated with medium phosphorous electroless nickel perform like stainless steel in many cases. Electroless nickel plates both internal and external surfaces, and will not build up on edges or ends, thereby providing excellent uniform coverage. With heat treatment, medium phosphorus electroless nickel can be hardened from 45 RCH to as high as 68 RCH.
Its characteristics include:
- 45-48 RCH as plated;
- 66-68 RCH post heat treatment;
- Good corrosion protection and lubricity; and
- Compliance with MIL-C-26074E, AMS 2404, AMS 2405 and ASTM B733 specification requirements.
► HIGH PHOSPHORUS: 10-12% (WEIGHT %) CONTENT
This coating provides maximum corrosion resistance. High phosphorus electroless nickel is standard in industries that require resistance to strongly acidic corrosive environments. It has a low degree of solderability, which makes it a desirable finish for electronics such as connector housings and semiconductor packaging.
Its characteristics include:
- Up to 44 RCH as plated;
- 46-48 RCH post heat treatment (4 hours at 350F, 1 hour at 750F);
- Excellent corrosion properties (over 1,000 hours salt spray test, passes nitric test);
- Non-magnetic properties; and
- Compliance with ASTM B 733 and AMS 2404 specification requirements.
► SEMI-BRIGHT MEDIUM PHOSPHORUS: 7-9% (WEIGHT %) CONTENT
This coating has very similar properties to medium phosphorus electroless nickel. It is primarily used for electronic applications due to its excellent solderability properties, as well as an underlayer for silver and gold plating. Its characteristics include:
- High hardness;
- Excellent solderability;
- Electrical resistivity;
- Good corrosion protection; and
- Compliance with MIL-C-24074C specification requirements.
► LEAD AND CADMIUM-FREE PHOSPHORUS: 5-8% (WEIGHT %) CONTENT
A lead and cadmium-free electroless nickel coating with the following characteristics:
- A melting range of 96o-1200o Celsius;
- 56 RCH as plated;
- 69 RCH post heat treatment;
- Magnetic properties; and
- Compliance with End-of-Vehicle Life Act, ASTM B733 and AMS 2404 D specification requirements.
Questions & Answers
How Does Electroless Nickel Plating Work?
Unlike electrolytic nickel plating, which relies on an electrical current to remove metallic nickel from the bath solution to deposit it on the surface of the substrate, the electroless nickel process uses a mix of catalysts to perform the same task. The advantage is a perfect uniformity. Electroless Nickel coating thickness is uniquely uniform regarding the geometrical form of the components being plated. The Deposit is an alloy of Nickel and phosphorus. It can be hardened by heat treated treatment up to 900 Vickers.
Electroless nickel can be enhanced with nano particles (ceramic, diamond, PTFE, Boron Nitride, silicon carbide) for special deposit characteristics.
What are the benefits of Electroless Nickel Plating?
You get the following advantages when you choose Compound Metal Coatings as your plating partner:
- improved corrosion resistance
- The ability to plate complicated and irregular shapes with very high size tolerances
- very good wear resistance
- EMI shielding
- mold release,
- anti galling
What base materials can be finished with Electroless Nickel Plating?
All metallic base materials, i.e. steel, high-alloy steel, stainless steel, aluminum, non-ferrous metals (copper, brass, bronze), and die-cast zinc. The suitability of further materials needs to be checked by means of sample coatings.
At CMC we are specialized to do Electroless Nickel coatings on very exotic substrates like titanium, carbide, TZM and combination of these material with Beryllium copper or other metals.
What electroless plating thickness are possible?
Depending on the application, it is possible to achieve plating thicknesses between 5µm and 75µm ( 0.0002 inch to 0.003 inch). In exceptional cases, a thickness of 100µm can be achieved (when using special rack systems)and special nickel solution.
What are the typical heat treatments for improving adhesion post Electroless Nickel Coating?
The baking temperature to improve adhesion depends on the substrate. Here are few examples:
- Aluminum alloys – 280-300 F
- Copper alloys – 320-370 F
- Steel & steel alloys – 360 – 400 F
- Nickel alloys – 400 – 450 F
- Titanium Alloys – 570-600 F
Time range from 1-4 h