History of ENC Coatings
Electroless Nickel Coating (ENC) has over 50 years of development history, all starting in the lab. To bring such a technology into industrial applications, early researchers/developers struggled with basic reaction principles, formulas vs. plating rates/qualities, long-term stable operation, stable quality thickness build up, standard operation procedures, hardening, bonding, etc. Successful applications of ENC started to show up in the late 1990’s when companies were able to generate good quality products in an economical manner. This was also in conjunction with much stricter bans placed on various electroplating operations due to environmental concerns.
For very strong corrosion resistance needs, organic and ceramic products have shown excellent results. However, their shortage on strength and expensive shaping costs have limited them from most applications. ENC – an amorphous mixture of nickel and phosphorous, provides both metal’s strength and excellent corrosion resistance (close to organic material). The extra advantage of ENC is that the coating can be hardened at a low temperature without deformation, which renders it self-lubricating. These advantages of ENC cannot be offered by electroplating (such as hard chrome) and immersion coating (such as zinc coating) products.
What exactly is Electroless Nickel Coating (ENC)?
ENC is a nickel-phosphorous alloy deposited by a chemical reaction from hypophosphite on a catalytic substrate, without the application of an electrical current. The coating thickness, anywhere from 0.0005 inch to 0.004 inch, is controlled by the length of time the metal substrate is left in the chemical bath solution. This autocatalytic chemical reaction deposits a controlled and uniform thickness even on complex part geometry and eliminates the need to mask off areas and grind weld seams. Another significant advantage of ENC is that clean, economical material such a new carbon steel does not need sandblasting prior to coating, nor being machined after coating. This reduces time and cost, as well as avoiding potential damage on delicate machined parts. ENC prevents corrosion on carbon steel, aluminium, brass, copper and high alloys such as Inconel.
Click HERE to view a paper created by Cenovus, in partnership with Harber Coatings, on the effectiveness of ENC coatings.
Current Developments of ENC Focus on the Following Aspects:
- Better corrosion resistance/wear resistance/bonding study of traditional ENC
- Industrialized multi-element platings (Ni-P-B, Ni-P-Co, etc.)
- Composite ENC (Ni/P/PFA, Ni/P/SiC, etc.)
- Aged ENC solution regeneration