What is ( Electroless Nickel High Phosphorus )ENHP?

ENHP is a chemical redox reaction process whereby a spontaneous chemical  reaction in weakly acidic solution produces a completely uniform metallic coating over the substrate surface. It can be applied to virtually any material to enhance  the hardness, lubricity, wear resistance, and corrosion protection of the surface  and thus increase the useful life of the product.

As a chemical redox reaction process any configuration of substrate can be  coated. Unlike chroming and the creation of electrical transfer, chemical redox  allows the plating of any configuration of substrate, from blind holes and bolt  threads to impellers. As plated, ENHP has superior strength and ductility to chrome; post-plating heat treatment has produced hardness values equivalent to hard chrome. Most noteworthy, ENHP has superior corrosion resistance, especially in acidic environments.

In some applications, after coating, the parts are exposed to a precipitation hardening process. This process precipitates nickel phosphide throughout the structure of the coating to increase the hardness and thus the wear resistance. For maximum hardness, this is done at 400 degrees C for one hour. A post plating bake not involving precipitation hardening can also be done at 250 - 270 degrees C for 5 to 8 hours to offer improved hardness and adhesion while maintaining a structure conducive to corrosion resistance.

Each new application requires a certain amount of engineering. It is important that the background of the substrate and the environment that the coating will be operating in be clearly understood. The coating process and requirements can be tailored to the specific application both from an economic and performance point-of-view. To best meet customer needs we have developed an Engineering Data Sheet, that once completed, provides the full spectrum of information required by Chetana

The key to the ENHP coating performance is the amorphous non-crystalline structure. A completely uniform amorphous structure is compressively stressed, eliminating any solution migration to the substrate surface. The strong bond between the coating and the substrate surface as well as the ductility of the coating preserve the amorphous structure even in abusive environments.

The hardness of ENHP is measured using a micro-hardness tester. It is an industry standard piece of equipment, using a very small indentation, done under a microscope. Results are reported using the Knoop or Vickers scale. Unlike the hardness of an uncoated material, the hardness of a coating is difficult to measure. Generally, the measurement must be made on the cross-section of a sample. Conversion of micro-hardness measurements to other scales can be done on a theoretical basis, but with the validity of such conversions subject to debate. ENHP hardness, as converted to Rockwell, measures approximately Rc 48 as plated and as high as Rc 68 after heat treatment.

ENHP can be chemically removed, or stripped, if required. For example, if ENHP is used on the inside cavity of a mould, the thickness of the coating can be monitored. Once the coating thickness is reduced to a predefined value, the remaining coating can be stripped off and a new coating applied. In this way, the coating is used as a long-life sacrificial surface and no damage to the mould occurs. Traditionally the surface of a mould is hardened using a process such as nitriding. When the hardened surface wears, the mould is eventually rendered unusable.

In applications where only portions of a part are to be coated, a masking agent is applied to the surface areas where the coating is not required. Masking can be labour intensive and therefore costly. In high volume production and repair part applications, it is often better to design the part to accept full plating.

No. Due to the superior ductility of ENHP and greater ultimate strength, a plated surface has much greater resistance to an abusive environment. Chrome, on the other hand, can de-laminate from a flexing substrate.

ENHP is most successful in a corrosive environment, especially acidic. The amorphous nature of the as plated deposit affords better barrier protection to many industrial parts including ball, gate, plug, and check valves, blow out preventers, chokes, heat exchange equipment, pumps, compressors, tubing vessels, packers, and more. Its high ultimate tensile strength and acceptable ductility afford success in an abusive environment. It often replaces stainless steel and more exotic alloys used in compressor blades, turbines, valves, pumps, extruders, and blowers. For unmatched wear, composite coatings of aluminium oxide, boron carbide, boron nitride, or tungsten carbide in an ENHP matrix have achieved this success. For sliding wear reduction, a dispersion of 20 % PTFE in the ENHP matrix has proven effective. For hardness values orders of magnitude superior to hard chrome, composite coatings including dispersions of diamond and silicon carbide in an ENHP matrix have proven successful on metal and ceramic grinding and cutting tools.