The Shop => Finishing => Topic started by: ieezitin on July 25, 2012, 02:13:24 PM

Title: Blackening of steel
Post by: ieezitin on July 25, 2012, 02:13:24 PM

Does anyone here know how to Blacken steel, I have been told that there is some products out there on the market that come in spray can form and some wash agents to achieve this effect. Al or little information would surely be welcome.

Thank you   Anthony.
Title: Re: Blackening of steel
Post by: Bluechip on July 25, 2012, 03:41:21 PM
Caswells ?? (
Which is a US company IIRC.
This is a process commonly used by gunsmiths, ( Parkerizing ?? ) there must be one nearer to you than us. We are not allowed to play with guns here.
Not even plastic ones.  :scratch:
Title: Re: Blackening of steel
Post by: 90LX_Notch on July 25, 2012, 03:43:26 PM

Number 492 of this thread-

I've used it with decent results.
Title: Re: Blackening of steel
Post by: Noitoen on July 27, 2012, 07:21:56 AM
A few months ago, I machined an adaptor for a R/C engine's propeller out of steel. He asked me how he could treat it without paint and I remembered an old trick I read somewhere. Degrease the part and wrap it in a lemon juice soaked tissue. After a few hours, the part had a grey anodized finish that looked really cool. Since the surface has an oxidized protection it is now rust proof.
Title: Re: Blackening of steel
Post by: Lew_Merrick_PE on July 27, 2012, 12:03:42 PM
Bluechip -- Parkerizing is a heavy phosphate coating (DOD-P-13232).  Black oxide finishing is an oxide conversion coating (MIL-C-13924).  They are different finishes.

Anthony -- It depends on what you want the black finish to accomplish for you.  At the simplest level, heating the part up to the very beginning of a "glow" and dumping it in dirty oil and then reheating it until the oil "flashes off" will give you a finish that will last for many years if no undue rubbing is involved.  I have tools that I made in the mid-1960's that were treated this way that have no rust whatsoever on them.  This finish will not stand up to friction or heavy solvents (alcohol is fine, acetone is death).  (US) Military armorers (read: gunsmiths) thoroughly clean their parts with acetone, dry them in an oven at 250F, and then place them in a sealed container with a couple of drops of fuming red nitric acid for a few hours as the pre-treatment.  The part is removed from the sealed container, exposed to steam, and allowed to sit in a still air location until and even sheen of rust has formed.  The part is then dunked in baking soda for a day or so (to halt the acid).  It is then boiled in a pressure cooker which will turn the rust to a black iron oxide coating.  It is polished (and, almost always, waxed) before being presented to the customer.  On the other hand, I have had good results with the Birchwood Casey & Caswell cold black finishes for steel (be sure that the lye has been well sealed against moisture).  The "Precision Brand" process has been a complete catastrophe both times I have tried it.

Just about any gunsmith worth his salt will have tanks set up for both Parkerizing and Black oxide finishing -- you may have to wait until he has enough parts to process to get it done at less than a rather high price.
Title: Re: Blackening of steel
Post by: John Rudd on July 27, 2012, 03:09:40 PM
I've used the 'heat it up and dunk in oil' process... with results I'm so far happy with although they have been small parts... :scratch:
Title: Re: Blackening of steel
Post by: rdhem2 on October 30, 2012, 12:18:20 PM
Brownell's, the great supplier of gunsmith tools and supplies from Mexico Mo. USA has a product called "OXYPHO Blue".  A cold process wipe on solution that is pretty durable, easy to apply and the metal does not have to be perfectly clean to work. And to top it off it is not very expensive and goes a long way.

Just my 2 cents worth.            :coffee:
Title: Re: Blackening of steel
Post by: SemiSkilled on October 30, 2012, 01:28:08 PM
for information, post 7

Title: Re: Blackening of steel
Post by: AussieJimG on October 31, 2012, 09:51:49 AM
I have used Blackfast (google it) successfully. It comes with everything you need: concentrate, containers with lids for the working solutions, well written detailed instructions and material safety sheets.