Metal finishing Q&As since 1989
-----
Electroless Nickel plus Chrome: harden at 600°C ?
Hello to all!
I should process an item by Electroless Nickel Coating + Chrome in order to increase the Anti-corrosion properties.
I read in a book (unfortunately without proper references) that the Chrome layer could negatively affect the corrosion resistance unless we proceed with a further thermal treatment at 600°C.
Has anybody ever heard it? If yes, could you suggest the references and even let me know if the thermal treatment should be performed prior or after the chrome layer?
Thank you very much in advance,
plating shop employee - Parma, Italy
December 1, 2009
Check your temperatures. At 600C the chrome plate softens severely vs as plated.
Most companies will bake the plated part at 375 F for 4 hours as soon as possible after plating for hydrogen de-embrittlement.
Electroless nickel is also hardened at that temp or a bit higher. EN can be hardened at 500F for a shorter period of time. I have seen a few references that use a short 600F for hardening some kinds of EN.
If this is done on hardened steel, it will lose a lot of its hardness, so there are a lot of trade offs.
600 °C is mega too high for most applications.
- Navarre, Florida
December 2, 2009
Many years ago I read a very well documented article which stated that the corrosion resistance of a steel surface coated with EN had been found to increase after a heat treatment at such high temperatures mostly due to an inter-diffusion process with the base metal forming a sort of nickel rich alloy on the surface. I cannot remember anything about chrome on top of it but it could behave in the same manner producing a more resistant alloy. I think it is worth investigating. Obviously, for this kind of treatments, it is imperative to have an excellent bond, free of entrapped contaminants to avoid blistering or flaking.
Guillermo MarrufoMonterrey, NL, Mexico
December 14, 2009
December 16, 2009
It is well known that nickel, under certain conditions , will alloy with select metals, to a varied depth.
I do not think that chrome will do this to any extent worth talking about. One thing for sure , is that chrome heated to 600C will be about as hard as frozen jello. If it is on hardened steel, the steel will be tempered to a very low hardness .
Without a very good reference of where and why it works or is desirable, I would not even consider it.
- Navarre, Florida
December 21, 2009
Hi James,
I agree with you. Perhaps the man has a confusion or semantics issue. In his heading he asks about hardness but the text focuses on corrosion resistance. It is not uncommon for inexperienced people to confuse both.
Best regards and happy seasons to you and all of those who make this forum the best through their excellent, frequent and generous contributions.
Monterrey, NL, Mexico
Q, A, or Comment on THIS thread -or- Start a NEW Thread