Electroless nickel plating is a process for chemically applying nickel-alloy deposits onto metallic substrates using an autocatalytic immersion process without the use of electrical current. It differs from electroplating, which depends on an external source of direct (electrical) current to produce a deposit on the substrate material. Since electrical current cannot be distributed evenly throughout the component, it is very difficult to obtain uniform coatings with electrolytically applied deposits. Electroless nickel deposits, therefore, are not subject to the uniformity problems associated with electroplated coatings.

Electroless nickel is the preferred choice among functional coatings for irregularly shaped, highly detailed part geometries because of its completely uniform deposit thickness and close dimensional tolerance capabilities . Electroless nickel deposits can also contain up to 25% PTFE (Teflon ® ), silicon carbide, diamonds or other alloying materials, which result in deposit properties for superior to those of conventional electro-plated deposits.

Deposit Uniformity

One especially beneficial property of electroless nickel is its uniform coating thickness, which can affect the ultimate performance of the coating, and can also eliminate additional finishing to be required after plating. With electroplated coatings, thickness can vary significantly depending upon the part's configuration and its proximity to the anodes.

With electroless nickel, the coating thickness is the same on any section of the part exposed to fresh plating solution, and can be controlled to suit the application. Grooves, slots, blind holes, and even the inside of tubing will have the same amount of coating as the outside part.

Corrosion Resistance

The corrosion resistance of an electroless nickel coating is a function of its composition. Most deposits are naturally passive and very resistant to attack in most environments. Their degree of passivity (and corrosion resistance), however, is greatly affected by their phosphorus content.

Often, the tramp constituents present in an electroless nickel bath are even more important to its corrosion resistance than its phosphorus content. Most coatings are applied from baths stabilized with lead, tin, cadmium, or sulfur. Code position of these elements in more than trace amounts causes a severe reduction in the coating's passivity and corrosion resistance.

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.

Industry Applications:

Electroless nickel coatings are most frequently found in the following industry applications:

• Aerospace, Appliance, Automotive, Chemical Industry
• Electronic, Engineering, Food Processing, Machine Tools
• Mining, Nuclear, Oil and Gas Industry
• Packaging, Petroleum, Plastic
• Printing, Steel, Textile, Transportation
• Offshore environments, Pipelines, Motor shafts
• Screw conveyors, Drum dryer rolls, Fuel pumps and nozzles
• ABS systems, Fuel injection pumps, Valves
• Reaction tanks and covers, Molds/moldings
• Magnetic memory disks, Heat exchangers
• Extruders, Brake cylinders, Steel cylinders
• Clutches, Pneumatic cylinders, Dough troughs
• Dryers and filters, Compressors and accumulators
• Dry cleaning machinery, Liquefied gas cylinders
• Food processing machinery, Hydraulic drilling and support equipment
• Drilling components