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Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Corrosion resistance of hard chrome vs. QPQ
Q. I am a Mechanical Engineer-turned-gunsmith and am looking for the most corrosion resistant metal treatment for gun applications. This is primarily for 4140 that must run on other pieces of 4140, with exposure to human sweat and/or salt spray.
Would hard chrome or Melonite provide the best long term corrosion resistance?
Which would hold up better in wear areas?
I am sorry if this has been asked before. I did several searches and read many old posts, but could not find the answer to my question.
Thank you very much for your help!
gunsmith - Cloquet, Minnesota, USA
August 21, 2008
A. Hi, Marc. Hard chrome is a great wear surface and is very low friction, but it is highly cracked and not highly corrosion resistant. QPQ is a good wear surface and more corrosion resistant. But it is generally a good idea that if two parts run on each other that they not both be the same material. Just as it is difficult to weld different materials together, it is difficult for them to cold weld or gall. Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
August 21, 2008
QPQ vs. Hard Chrome for gate valve stems
Q. I'm looking to coat the valve stems on our gate valves to allow them to "wear" better in the field. They are made of 17-4 and I'm looking at either QPQ or Hard Chrome ... which will wear better against H2S gas and heat?
Randy Guillory- Magnolia, Texas, USA
February 18, 2014
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