Letter 11290

Difference between Nickel plating and Electroless nickel

Can anyone explain the end physical properties difference between electroless and electrolytic nickel plating. Would hard chrome offer improved corrosion and/or physical properties.

Glen McIntosh
- Wisconsin

Electroless nickel is far superior to electrolytic nickel for corrosion resistance. That is because it is an amorphous glass-like nickel phosphorous alloy and because the thickness distribution is far superior so there will be no thin spots. Hard chrome is not really corrosion resistant since the cracks extend through to the substrate.

Ted Mooney, P.E.  finishing.com Brick, New Jersey

Electrolytic nickel is deposited using DC current, while Electroless Ni is an autocatalytic deposition. Electroless Ni produces plating of uniform thickness all over the part, while electrolytic Ni plates a thicker deposit in high current density areas. Electrolytic nickel is more ductile than electroless, which tends to be brittle and glasslike. Typical electroless Ni baths use hypophosphite reducing agents and deposit phosphorus along with the Ni. Mid-Phosphorus (5-8%P) deposits are bright, hard, and magnetic as deposited. High phosphorus (9-15%) deposits are nonmagnetic as deposited, semibright, and slightly softer than mid-phos. High-phos Ni has greater corrosion resistance than lower phos deposits. All electroless Ni deposits can be altered by heat treatment at temperatures as low as 800 F. Electrolytic deposits are Ni-Sulfur alloys if a brightener is used. The sulfur in the deposit reduces corrosion resistance.

Michael Brewington
- Salisbury, Maryland

Hi Glen:

You already got two professional answers, but adding to Ted and Mike, here are some other physical properties that you asked for. Chromium is harder(900-1100 HV), has a lower thermal expansion (around 8/1000000)and has a higher melting point(1875-1920 deg C) than any nickel, either electro or electroless. Most of the time is stressed and cracked, so it is not an impervious barrier to isolate substrates chemically, but it will resist nitric acid and other strong oxidants better than either electro or electroless nickels.

Guillermo Marrufo
Monterrey, NL, Mexico

There is one thing that I would like to add on top of the comprehensive explanations that you already received, the low phosphorous EN deposit is almost as hard as hard chromium. That is why some platers use it as a substitute to hard chrome.

Sara Michaeli     chemical process supplier Israel

I just want to add one important thing that should be taken in consideration now with ROHS and WEEE regulations : most of the formulations of these electroless Nickel bath use Lead and Chromium as stabilizer and brightener. And these 2 elements codeposit with the Ni alloy.
Some substitutions are coming on the market but are not yet common.

Franck MASETTO
- China

Ed. note: the above posting is a few years old and most suppliers now offer electroless nickel without lead or cadmium stabilizers.

i want to know which method can take more time electrolytic or electroless.

dilip patel
plating shop employee - gujarat-jamangar, India

Hi, Dilip. Electroless nickel usually takes longer. Plating times of 1 to 2 hours are fairly common while an hour is a long time for electrolytic nickel plating.

Regards,

Ted Mooney finishing.com Brick, New Jersey