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Difference between Nickel plating and Electroless Nickel plating
Q. 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
A. 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. RET
finishing.com
Brick, New Jersey
A. 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, semi-bright, 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
A. 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 it 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
A. 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
A. 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 co-deposit with the Ni alloy.
Franck MASETTO
Some substitutions are coming on the market but are not yet common.
- China
Ed. note: the above posting is a few years old and most suppliers now offer electroless nickel free of lead or cadmium stabilizers.
March 25, 2009
Q. I want to know which method takes more time electrolytic or electroless.
dilip patelplating shop employee - gujarat-jamangar, India
March 30, 2009A. Hi, Dilip. Electroless nickel usually takes longer. Plating times of 1 to 2 hours are fairly common, while an hour is a very long time for electrolytic nickel plating. But please don't read too much into my answer, because 'productivity' is almost never any consideration in choosing electroless vs. electrolytic.
Regards,
Ted Mooney, P.E. RET
finishing.com
Brick, New Jersey
January 15, 2012
Hi.
We are using MIL standard QQ-N-290A for Ni Plating. It states Nickel Plating (Electrodeposited) on its header. I cannot make it out whether this is Electroless or Electrolytic process.
Secondly, we are much concerned about RoHS environment. So can you give suggestion what process we should follow, Electroless or Electrolytic?
Thanks
Mihir
- Sydney, NSW, Australia
January 16, 2012
Hi, Mihir.
"Electrodeposited" equals electrolytic, so QQ-N-290A describes electrolytic nickel plating; but it is cancelled, so please obtain AMS-QQ-N-290.
Many suppliers have reformulated their electroless nickel processes to be free of cadmium and lead for RoHS compliance, but you should check. RoHS compliance may be required for your parts, and is advisable in any case, but is not a driver in deciding whether to use electrodeposited vs. electroless nickel.
Regards,
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 Ted Mooney, P.E. RET finishing.com Brick, New Jersey |