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-----Black oxide / blackening steel heat treatment
Q. Hi,
I have the following questions and would appreciate an answer:
a) In Heat Treatment, is their any difference between Black Oxide and Blackening?
b) We are looking for some kind of blackening process wherein the anti-corrosion resistance of 12L14 Carbon Steel is improved but the heat treatment process must not add hardness nor cause any dimensional growth (as in plating). Could you suggest something and any vendors in Southeast USA who are involved in this business.
Thank you,
- Peachtree City, Georgia, USA
2002
A. Hi Naveen. I don't know much about heat treatment, but it doesn't sound like you're actually talking about heat treatment anyway. "Blackening" and "black oxiding" are slang, not a specification, but in this context they are probably the same thing, and are achieved by putting the parts into an aqueous based solution of sodium hydroxide and oxidizing/blackening agents such as nitrates at about 230°F.
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Ted Mooney, P.E.
Striving to live Aloha
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2002
A. a) Black Oxide is one of several Blackening processes. These are not normally considered heat treatments, and several processes form a black coating (e.g., copper selenide) on steel at room temperature. The hot black oxide process described in MIL-DTL-13924
[⇦ this spec on DLA] does not affect the metallurgical properties of many steels and hence is not considered heat treatment. It does involve limited heat treatments, e.g., stress relief and hydrogen relief bake-out, for hardened steels (> 40 HRC).
b) For this 'Mission Impossible' use a force-field from Star Trek. The corrosion resistance of black oxide is primarily due to a supplemental oil or wax. Good protection may require measurable wax or lacquer thickness. Black chromium (electroplated, ~0.00001"), is more protective and can also be oiled. It is normally applied over a chrome or nickel basecoat, but can be directly deposited. Use the 'Jobshops' link below to find a finisher with whom you can discuss your options. In any case, inform the metal finisher of the lead content of your steel, as additional pretreatment is normally required.
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
2002
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