BLACK OXIDE ON 4140 PH BLACK OXIDE ON 4140 PH engiNERD77 (Agricultural) (OP) 22 Aug 17 13:08 WILL THE A CALL OUT FOR BLACK OXIDE GIVE THE SURFACE RESISTANCE TO RUSTING? RE: BLACK OXIDE ON 4140 PH arunmrao (Materials) 22 Aug 17 14:56 No capital letters please. "Even,if you are a minority of one, truth is the truth." Mahatma Gandhi. RE: BLACK OXIDE ON 4140 PH ironic metallurgist (Materials) 22 Aug 17 16:14 Capital letters or not, I can't make sense of the post. RE: BLACK OXIDE ON 4140 PH djhurayt (Mechanical) 22 Aug 17 20:34 black oxide will only provide minimal rust resistance RE: BLACK OXIDE ON 4140 PH EdStainless (Materials) 22 Aug 17 22:29 often black oxide is then treated with oils or waxes in order to provide some short term corrosion resistance. = = = = = = = = = = = = = = = = = = = = P.E. Metallurgy, Plymouth Tube RE: BLACK OXIDE ON 4140 PH engiNERD77 (Agricultural) (OP) 23 Aug 17 11:29 Thanks guys! Pretty much what I had read about. RE: BLACK OXIDE ON 4140 PH tbuelna (Aerospace) 24 Aug 17 00:16 engiNERD77, You didn't provide the process spec for your black oxide coating, but MIL-DTL-13924 is a commonly used one. Your 4140 Pre Hardened material would use MIL-DTL-13924 class 1. If the final material hardness is >Rc39, you will also require hydrogen embrittlement relief treatment. I would highly recommend taking some time to educate yourself a bit about the black oxide process and the coating characteristics. Understanding the process steps, quality assurance requirements, specifying supplementary treatment, etc. will be very helpful when specifying the coating on your engineering documentation and preparing vendor work orders so that your delivered product is exactly what you want. MIL-HDBK-205 is an excellent reference on the subject.