We have been specifying 'blackened steel' (i,e. chemically treated mild steel to give a natural, blackened finish) for quite a few years and EVERY time we ask a contractor to tell us what the chemicals/method is for this they clam up like its a top secret or something. I'm not talking about powdercoating, or spray painting, but a mix of chemicals applied to the mild steel which then turns it black - it is like 'gun blackening' where small parts are dipped into a tank of chemicals and then the steel goes black, however this is much harder to do on large sheet metal and architectural elements. The end result should be a natural looking steel with nuances in colour and pattern, but an overall darker 'black' than the natural mild steel would have by itself - and where there is welding, grinding, etc - the chemical blackening makes this go black as well.
So the question is what are the chemicals and application method to achieve this finish?
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Answers (5)
Anthony, Architect • 2016
Armorers created blackened steel in the Renaissance with linseed oil. They heated the steel and applied the oil in much the same fashion described by "grahame-white" above. It probably is a little less toxic than old motor oil, and because it requires multiple applications, allows for a broad color range of "blackening" .
Grahame, Architect • 2016
HI
When I did O Level metal work at school. we were taught a blackening method for mild steel. This involved heating the metal to a blue heat and then quickly immersing in old engine oil. - I bet they do not teach that method any more....( fumes and hot working...) It did however make a very pleasing finish.....
dan robert, Architectural Draftsperson • 2016
Look into the work of Ron Young of Sculpt Nouveau. He works out of Escondido in San Diego County, CA and has posted videos on Youtube.
BERNARD, Architectural Draftsperson • 2016
http://www.mmsonline.com/articles/do-it-yourself-cold-blackening
Scott, Architect • 2016
I have no idea, but a bit of research uncovered it's to do with:
Basically, the blackening process choice for shops is hot or cold. Hot oxide uses a caustic soda bath operating at 285 to 290oF. Generally, these tanks are gas fired to keep the caustic soda solution at a boil. Obviously, working around these tanks is unpleasant, which is one reason why many shops with hot lines opted to remove them and sent the work out.
It's seems every shop does it slightly different, which maybe why they keep it a secret.