Electroless Plating

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Differences of Electroless Nickel by percentage of phosphorus content

By varying the percentage of phosphorus or boron in the coating, deposits can be produced to exhibit non-magnetic and highly corrosion resistant characteristics or hard deposits with excellent wear resistance.

Ideal for electronic parts, functional and engineering applications.

Low Phosphorus

High Hardness (58 - 62 Rockwell C)
Superior Wear Resistance
Low content of phosphorus (1 - 3)
Excellent erosion resistance
Melt Point up to 1205.4 C
Semi Bright
Better conductivity
Ideal for electronic parts, functional and engineering applications
Densitiy 8.5 gm/cm3
Electrical Resistivity 20uO cm

Medium Phosphorus

450 Knoop hardness (kg/mm2)
Medium content of phosphorus (7 - 8)
Melt Point up to 960 °C
Semi Bright
Good conductivity
Ideal for electronics, aerospace, automotive, hydraulic equipment, moding and industrial parts
Non-magnetic

High Phosphorus

Compressed pressure
450 Knoop hardness (kg/mm2)
Good lubrication, wear resistance and abrasives
High phosphorus content 10.5% – 12%
Excellent corrosion resistant
Melt point 880 C, ideal for brass and normal solder
Semi Bright
Low conductivity
Electronic, gas, oils, printing, aerospace and chemical industries
Non-magnetic
Density 7.75 gm/cm3 if phosphorus is 10.5%
Ideal for high thickness deposits > 400 micro inches
Long live and stability
Minimum porosity

Electroless Nickel Melting Point

Low phosphorus = wider melt point
Medium phosphorus = narrow melt point

Deposit Uniformity: Uniform coating thickness from inside through the outside

Electroless Nickel vs Electrolytic Nickel

Electroless Nickel

None using current
None using current Uniform/evenly deposit due to auto catalytic immersion
Preferred for un shaped parts, geometrically difficult
Modulus of Elasticity
Excellent adhesion
Gloss: Vary from matte to very bright depending on the metal
Matte: Corrosion protection, good deposit elongation and low stress of high thickness with minimum pitting
Very bright: Not recommended for idem.
SS: Need a thin nano layer of electrolytic Nickel and then electroless nickel to achieve adhesion
Aluminum: Needs bake after plating
Solder: Excellent
Welding: No

Electrolytic Nickel

Applied by electrical current
Non-uniform deposits due to electricity
Preferred well-shaped parts
No elasticity

Applications for Electroless Nickel

Electroless nickel is normally applied for five different applications: coatings used for corrosion resistance, wear resistance, lubricity, solderability, or buildup of worn or over-machined surfaces. To varying degrees, these properties are utilized by all segments of industry, either separately or in combination.

Petroleum and Chemical Industries

The petroleum and chemical process industries are the largest users of electroless nickel for corrosion protection. High phosphorus coatings are commonly used to resist corrosion and erosion in aggressive brines, acids, and gasses. Common applications include valves, chokes, blowout preventers, mud pumps, sucker rod and submergible pumps, pipe, heat exchangers and separators, packers, safety valves, production tubing, and all types of downhole tools.

Medical, Dental and Pharmaceutical

Electroless nickel is also used for medical, dental and pharmaceutical equipment because of its superior corrosion and wear resistance. This equipment is often subject to severe abuse, but must remain completely reliable. Electroless nickel provides almost complete resistance to these environments and frequently allows steel or aluminum to be used instead of more expensive stainless steel.

Typical medical applications are scissors, suture needles, clamps, forceps and hubs for disposable hypodermic needles. In the pharmaceutical industry, extruders, sizing screens, pill sorters and filing equipment are common applications.

Printing and Textile Industries

The use of electroless nickel for the cylinders and rolls used in the printing and textile industries has grown greatly during the past several years. The ability of the coating to deposit uniformly allows the cylinder to be machined to size, balanced, and plated without subsequent finishing or grinding. The life of the equipment is also greatly extended by the lubricity and wear resistance of electroless nickel. Other common textile applications include thread guides, fiber feeds, fabric knives, heddles, bobbins, shuttles, rapiers, ratchets, knitting needles and picks.

Aerospace

In the aerospace industry, electroless nickel is used to protect the surface of light metals, such as aluminum, from corrosion and wear. It also enhances the appearance of these metals with a polished, stainless steel look. The coating is used on a variety of aircraft parts, including engine components, structural air frame and landing gear pieces, refueling systems, compressor blades, and servo valves. Its uniform thickness, and its ability to coat the inside of holes and recesses, makes electroless nickel an ideal coating for welded tanks and complex hydraulic valve and manifold systems.

Packaging and Handling

With packaging machinery and food handling equipment, electroless nickel is also used because of its excellent wear and corrosion resistance. The coatings provide an attractive finish and help to ensure the cleanliness of the part. Electroless nickel is used to handle such diverse products as sodium hydroxide, food grade acids and fish oils. Its uniform deposit is especially useful for hydraulic cylinders, worm feeds and extruders, shafts, chain belts and other close fitting parts. Common food handling applications include pneumatic canning machinery, hamburger molds and grills, bun warmers, baking pans, fryers and chocolate molds.

Wood, Pulp and Paper

Wood handling, pulp and paper equipment operate under conditions of severe corrosion and abrasion. The salt and organic acids present in woods can cause high rates of attack on common materials. Electroless nickel coatings provide good protection against these conditions and are presently being used for knife holder cover plates and for abrading plates for wood cutting and chopping machines. Differential pins are also a large application area.

Automotive

Except for plated plastics, components for the automotive industry historically have provided only a limited market for electroless nickel. With the longer lives and greater reliability now required for automotive components, however, more and more applications for the coating are being developed. Some existing applications are pad holders for disc brakes and brake cylinders, synchromesh gears, piston rods, shock absorbers, steering assemblies, mufflers, exhaust pipes, exhaust manifolds and lock components. Differential pins are also a large application area.

Molds and Dies

The ability of electroless nickel and electroless nickel/PTFE coatings to provide a uniform deposit, even into deep recesses, helps to ensure that the finish on a mold will duplicate the original surface. The natural lubricity of the coating provides smooth flow during injection and quick and easy release of the part. Because of its high hardness at elevated temperatures, electroless nickel minimizes erosion and abrasion of molds and dies and helps to extend their lives. The coating also provides excellent protection against the corrosive fumes produced during molding such plastics as ABS, PVC, polycarbonate, acrylics and materials with thermoplastic additives. Similarly, electroless nickel has been found to provide a superior coating for zinc diecast dies and glass molds.

Electronics

Coaxial connectors, headers, housings and cases, heat sinks, diode cans, shutters, interlocks and memory disks and drums are among the many electronic applications presently plated with electroless nickel. For electronic components the coating is used for its combination of superior corrosion resistance and solderability. Other important considerations with these components are the coating’s uniform thickness and its consistent electrical, thermal and physical properties.

Salvage and Repair

Electroless nickel coatings are very cost effective for salvage and repair. Because of its superior adhesion, uniform and accurately controlled thickness, and excellent wear and corrosion resistance, these coatings are often used to selectively build up worn or mis-machined parts. The cost savings from such repairs are often substantial, since they not only allow mis-machined parts to be used and thus avoid their remanufacture, but this also allows the manufacturing facility to increase the production of new parts and improves productivity.

Mining

Equipment for mining operations is a growing application for electroless nickel coatings. Mining environments are both very corrosive and abrasive. Mine waters are typically acidic and can cause high rate of attack of unprotected steel. In addition, the dust produced during mining can result in severe erosion. Electroless nickel coatings have been found to withstand these conditions with little attack. Common applications are hydraulic components, framing, cylinder heads for jetting pumps, pipeline connections and tubing, and mine engine components.