Electroless Nickel Plating

About Electroless Nickel Plating and Electroless Nickel Including: Cadmium Plating, Chrome Plating, Copper Plating, Electroless Plating, Gold Plating, Metal Plating, Nickel Coating, Nickel Plating, Rhodium Plating, Silver Plating, Tin Plating & Zinc Plating.

Electroless nickel plating is a process in which a coating of a nickel alloy (most commonly nickel-phosphorus) is deposited onto a metallic substrate. This is a procedure that uses heat, which is directly linked to the chemical reduction of nickel compounds. Unlike electrolytic coatings, electroless nickel plating is performed without the use of electricity. Electroless nickel plating also has better corrosion resistance compared to other coating techniques. Any substrate surface to which the coating solution has free access is capable of being coated or plated.
 
Electroless nickel plating was first reported in 1946 by its accredited discoverers, Grace Riddell and Abner Brenner. Nowadays, technology and education have enabled the advancement of the nickel plating process. Electroless plating is superior to electrolytic plating in its ability to coat uniformly. There is also less excessive buildup on projections and corners. Because of its benefits, electroless nickel plating is a favorite for coating irregular objects that other processes have difficulty covering. Products that have already been coated with electroless nickel can undergo heat treatment in order to precipitate phosphorous from the alloy, which increases hardness up to four times.
 
Various nickel deposits are available based mainly on the phosphorus concentration. Low phosphorus deposits (1-4%) have the ability to be welded or brazed, and are very corrosion resistant. For applications where lubricity and heat tolerance are desired, a medium phosphorus concentration (5-9%) is more beneficial. Maximum corrosion resistance for nickel plating comes with a higher phosphorus concentration (10-15%). High amounts of phosphorus add to the deposit's non-magnetic and excellent ductile qualities. Another property of phosphorous electroless nickel that makes it highly beneficial is its ability to adhere to most metals.
 
Some examples of industries that use electroless nickel plating include the petroleum, medical, dental, oil, gas, aerospace and automotive fields. After choosing the deposit best suited for a particular application, the thickness of the coating should be considered. Coating thicknesses for electroless nickel plating range from less than .0005 inches to over .01 inches. Thicker coatings often mean better corrosion resistance and better wear characteristics. This provided, finding a quality finisher is crucial in receiving a quality product. With all the advancements in electroless nickel plating, it is surprising that the exact mechanism for the deposition remains unknown, due to its complexity.

Types of Electroless Nickel Plating

• Chrome plating is a finishing treatment that can be either bright chrome or hard chrome.
• Composite coatings use hard particulate matter mixed with electroless nickel plating chemicals. Silicon carbides and synthetic diamonds are common types of composite materials.
  
• Electroless nickel/Teflon® composite plating creates a slick, low friction surface.
• Electroplating is an alternate type of the coating/plating process. Using a low voltage current, charged nickel compounds are attracted to a substrate's oppositely-charged surface; in this fashion, nickel deposits are transferred through a solution and onto the substrate.
  
• High phosphorous plating has the best corrosion resistance of any electroless nickel plating process. It is used in harsh environments, such as oil drilling and coal mining.
  
• Low phosphorous (hard) plating yields very good resistance to alkaline corrosive environments. It also provides uniform thickness, so that grinding after the procedure is unnecessary.
• Medium phosphorous (bright high speed) plating is a popular form of nickel plating that has been used over the years. It generates a nice uniform coating and will not build up on the edges of the substrate.
• Metal finishers improve a product's corrosion and wear resistance.
• Metal-plating is the process of depositing a metal or metal alloy onto a surface.
• Nickel-boron coatings are admired for their as-plated hardness, which is greater than that of nickel-phosphorus platings. The melting point for N-B alloys is higher than that of N-P, but chemical costs for nickel-boron baths can be up to 10 times that of the nickel-phosphorus chemicals.
• Nickel coating is the process of coating an item with a nickel alloy to prevent oxidation.
• Poly alloy coatings consist of nickel and boron or phosphorus. Other materials, such as iron, cobalt and tungsten, are also included in poly alloys. Polly alloy coatings allow maximum corrosion and high-temperature resistance, hardness and magnetic or nonmagnetic qualities.

Electroless Nickel Plating Terms

Abrasion - The deformation or wearing away of a surface material due to frictional forces and/or impact engendered by a nearby body or element.
 
Activation - The loss of passivity on the surface of a solid.
 
Adhesion - The sticking together or attractive force between two materials in contact. The adhesion that electroless nickel provides to most metals is excellent.
 
Alloy - A solid compound consisting of two or more metals fused together.
 
Anode - A positively-charged conductor that attracts nearby free electrons. Anodes are a uniformity factor for the electroplating process, but not electroless plating.
 
Base Metal - Metal that easily oxidizes or dissolves, forming ions.
 
Bright Dip - A process that is used to create an extremely bright surface on a metal.
 
Catalysis - The quickened rate of a chemical reaction due to a catalytic agent. Catalysts are often applied to substrates to speed up the finishing procedure.
 
Coating Thickness - The distance from the top layer of the coating material to its substrate's outermost surface. Common thicknesses for nickel deposits range from .0005 to .001 inches.  
 
Compound - A substance formed by the chemical union of two or more elements.
 
Conductance - A metal's capacity to transmit electric current.
 
Corrosion - The deterioration of a metal due to reaction with atmospheric elements. Nickel plating is admired for its anti-corrosive qualities.
 
Deburring (http://www.iqsdirectory.com/deburring-equipment/) - The removal of burrs and sharp edges on a metal by chemical, electrochemical and mechanical processes.
 
Density - The ratio of a material's mass to its volume. Nickel compounds used for coating purposes typically have densities in the range of 7.7 gm/cm³ to 8.5 gm/cm³, depending on the concentration of phosphorus.
 
Ductility - The ability of a metal to withstand deformation before finally fracturing.
 
Electrical Resistivity - The ability of a material to resist the flow of electrical current.
 
Eutectic Alloy - An alloyed material that has a melting point lower than that of each individual element alone.
 
Hardness - The resistance of a material to deformations by indentation. For electroless nickel plating, common hardness values range from 44 HRC to 59 HRC.
 
Immersion - The act of submerging a product. Substrates are immersed into baths containing electroless nickel plating chemicals.
 
Ion - A charged atom or molecule.
 
Oxidation - A reaction in which electrons are removed from a reactant, usually because of the addition of oxygen.
 
Passivity - A decrease in the corrosion rate of metal, which results from the application of a protective film such as electroless nickel plating.
 
Substrate - The material that is being coated or plated.
 
Tensile Strength - The maximum amount of tensile force that can be applied to a material before it is broken apart. Electroless nickel plating has comparable tensile strength to many hardened steels.
 
Topography - The surface features of a material. Substrate topography affects coating appearances for many metal products.