Electroless nickel plating is a process that deposits a nickel-phosphorous alloy onto a component without an electric current. This gives the coating more durability, and it can be applied to a wide variety of parts.
ENP is an excellent choice for corrosion-resistant metal components that require a bright appearance while retaining magnetic properties and solder-ability. It can be plated with low (2-4%), medium (5-9%), or high (10-14%) phosphorus levels.
Corrosion Resistance
Electroless nickel plating is a very effective corrosion protection coating. It can be used to protect components in a wide range of industries, including industrial machinery, automobiles and even oil & gas production equipment.
Corrosion is a major concern in many products and environments. The ability of a metal to resist corrosion and oxidation helps it function better and last longer.
One of the primary corrosion resistance benefits of electroless nickel is its excellent resistance to rust formation. This coating is ideal for protecting a variety of metals, including steel, brass, and copper.
Corrosion resistance is affected by the phosphorus content of the deposit, as well as post-plate heat treatments. High-temperature bakes can cause the amorphous structure of medium and high phosphorus deposits to transition into crystalline structures, which increases hardness and lowers corrosion resistance.
Wear Resistance
Electroless nickel coatings are formulated to provide excellent corrosion protection. Their pore-free and chemically resistant deposits can withstand more than 1000 hours of salt spray exposure on properly prepared basis metals.
The amorphous structure of the nickel phosphorus (Ni-P) alloy in these deposits prevents grain boundaries that can create initiation sites for corrosion. This amorphous structure also provides good wear resistance and natural lubricity, which reduces galling on opposing surfaces.
These hard, abrasion-resistant deposits can be heat treated to further increase their hardness. They are highly wear-resistant and can be used to replace stainless steel in a variety of applications, including sprockets and gears, pump parts, machine components, valves and more.
The density and thickness of these coatings depend on the phosphorus content in the bath. Mid phosphorus coatings contain between 5% to 9% phosphorus and are the most common.
Coating Uniformity
Electroless nickel plating is a very common and versatile corrosion resistance coating method. It can be applied to a wide range of metals, including stainless steel, aluminum and copper alloys.
It’s also a great choice for parts that have to be used in high-corrosive environments. This is because it resists saltwater, acid, carbon dioxide, oxygen and hydrogen sulfide for a much longer time than a traditional coating, which can deteriorate after 48-100 hours of exposure.
In addition to its corrosion protection, electroless nickel can also provide a hard and wear-resistant surface on metals. This makes it the preferred choice for parts that require superior lubricity, durability and conformity to tight tolerances.
Black electroless nickel plating can be done with a low phosphorus bath (1-4 percent), a mid phosphorus bath (6-9 percent) or a high phosphorus bath (11-14 percent). The amount of phosphorous in the electrolyte bath determines the density and thickness of the electroless nickel coating.
Hardness
Electroless nickel plating uses a chemical reduction process to deposit a nickel-alloy coating. This process does not require the electric current used in electrolytic processes, and it is less prone to surface impurities that can occur when using an electric plating method.
Depending on the nickel alloy and the type of bath, ENP can be applied to a variety of substrates. Typically, it is applied to aluminum, tooling steels and carbon steels.
The hardness of an electroless nickel coating depends on the phosphorus content in the plating bath. The lower the phosphorus, the harder the coating will be.
Low phosphorus electroless nickel (ENP) coatings offer the highest as-plated hardness, although they are also the least ductile. Medium and high phosphorus varieties provide more corrosion protection, a higher melting point, and improved conductivity in the as-plated state.
