Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Coloring and Blackening of Stainless Steel
Q. Hello. Greetings from Argentina !
I'm Industrial Engineer, and I work with Stainless steel for a body jewels company.
I found a chemical solution for blackening steel (316L and 304). Yesterday, I test it. It's Good! But I lost the shiny surface.
Basically, the solution is Molten Sodium Dichromate. Immersion of the piece about 5 minutes at 300 C.
I need to know if this method can change the biocompatibility of the steel. And if is possible obtain a bright surface, like before the immersion?
If it is possible to, the method for coloring the steel. Thank you very much.
Industrial Engineer - Capital Federal - Argentina
2007
A. Sodium dichromate is carcinogenic compound and I think you can't use it on jewelry items. You can silver or copper plate stainless steel; after that you can treat it with potassium polysulfide solution. Or you can use old burnt oil process -- oil it very slightly with linseed or any other edible oil (or 20% shellac solution), then heat it slowly to max. 400 °C (with hot air gun). Hope it helps and good luck!
Goran Budija- Cerovski vrh Croatia
Wake up US manufacturing - this used to be a predominantly US dominated website - both questions and answers. Now we've got Argentina posting questions and Croatia responding. Anyway . . .
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A. There are alkaline black oxide processes specific for 300-series stainless that don't significantly dull down the surface. They basically convert iron to the black form of iron oxide (as opposed to the red form, i.e., rust as we all know it). I can't see how that would change anything in the "biotoxicity" of the parent stainless steel provided that it's rinsed well.
Milt Stevenson, Jr.
Syracuse, New York
opinion! Yes the site used to be USA-dominated, Milt, but of course reflects the world situation. None of the "big three" plating process suppliers is American anymore, and most of the 2nd-tier process suppliers market to and manufacture in China. Most large USA equipment installations are by Europeans these days. Attendance at AESF meetings is discouraging. I know three good-size NJ plating shops that closed this year. The "arsenal of democracy" is empty with no manufacturing capacity left to refill it, and nobody is appropriately scared. Like you, I do what I can, including keeping this site going, but the American public doesn't know or care about the straits we are in. (Well, this thread earned a big red "opinion!" sticker). Ted Mooney, P.E. Striving to live Aloha finishing.com - Pine Beach, New Jersey Well, its sad to hear that the so-called experts in this website or the guys running this site feel that this website was created for US people. In the first place the website is "www" means world wide web, from the word itself world wide, so it means it people from all over the world with metal problems come here for a consult or try to have an opinion on what's going on with their metal stuff. You might as well change the name US.finishing.com, so that it would be exclusive for white Americans with big ego's know everything "expert in everything". - Cebu, Philippines We're delighted to print your opinion, Barry, but the only person who has insulted anyone is you. Yes, I grieve that many of my friends lost their life's work recently and had to discharge their employees due to my country's inattention to the direction we're headed, and I won't apologize for grieving :-( But you should apologize for your remarks :-) BTW, the three New Jersey shops that I mentioned closing this year were also all advertisers who had been helping make this site possible for the world to benefit from; you apparently feel entitled to have such forums, but they can't exist unless someone pays the costs and I don't see your company supporting this forum :-) Ted Mooney, P.E. Striving to live Aloha finishing.com - Pine Beach, New Jersey opinion! I know almost nothing about coloring of SS, Mr. Umacob, and that's why I didn't comment, but I know about generosity and democracy. You're right on the www concept, but the rest of your opinion seems out of context, emotional and unfair. Milt was trying to encourage his US colleagues, not to exclude or devalue people from other countries. He also gave an expert opinion to the inquirer. That's generosity. Ted shared a well informed view and critique of the situation in his own country without offending others. He also swallowed his pride and posted your letter. That's democracy. My vote goes for them, and that's a red sticker too! Guillermo MarrufoMonterrey, NL, Mexico As you said, this site was set up initially and intentionally in USA, now it goes world wide, Does not it mean you are very successful? Is not that why you get so many advertisers (sponsors)? Be chemical suppliers, instrument manufactures... You are painful to see some plating shops close down, you will be (me too) more painful to see this site shut down. We understand your feeling for this, but you need to understand also that it is just like two sides of one coin, at one side, plating houses closed for the so-called globalization, but at the same time on the other side, chemical suppliers and instrument manufactures in USA make lots of money from the so-called globalization too. John Hu- Singapore Thanks, John! I said the site was dominated by USA visitors years ago; I didn't say it was set up for the USA, and it wasn't. Rather, it's been online since before the internet existed, back when people had to pay for the phone call; so, due to the high cost of international long distance calls, nearly all visits were from the USA in the early days. My visit to Singapore some years ago remains one of my fondest memories and I wish you and your countrymen all the best. The fact that I am pained by the current anti small business attitude of my own government and our own people doesn't mean I bear ill will towards people in other countries. I've learned a great deal both technically and about life from the postings here and I feel HONORED when people like Ezequiel, Goran, Barry, Guillermo and you choose to use this site. Ted Mooney, P.E. Striving to live Aloha finishing.com - Pine Beach, New Jersey I think the Webmaster is very much right on. Our work has gone overseas, and I celebrate our foreign counterpart's success. The Lord of Commerce has smiled on them, and it is their day. - Oxford, Alabama |
Q. It appears that the original question was lost in the ensuing (and well stated) responses.
Can stainless steel be colored in a biochemically compatible way?
Yes! Interference colors can be developed on the surface of the material, and without minimizing the underlying brilliance of the stainless steel. These colors result from a phase shift in the incoming light source, much the same way as sound modulations occur when two notes are played that are slightly different in pitch.
I wish you well in your chosen field.
JimC
- Colorado Springs, Colorado, USA
2008
Thanks for the fine technical answer and the kind words, Jim.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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