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Ian B
03-02-2011, 04:40 AM
There have been various threads on metal blackening, but most processes don't seem to work on stainless steel (the common ones; 304, 316). I'm looking for a purely decorative finish. Being on stainles, it doesn't need to impart any particular anticorrosiveness, just look nice and black - sort of a stove black.

I found these references: http://actonmetal.com/passivating.html

Seems they use nitric acid and sodium dichromate, in a cold or hot process. Anyone have experience with this method?

Sodium dichromate is available via ebay; nitric acid looks a bit more challenging to get hold of, especially in Holland. Sulphuric is available as battery acid - does nitric have a similar commercial application?

Ian

Westline
03-02-2011, 07:57 AM
Hey Ian.

I read up about this when I did my research on black oxide.
The best would be to check out http://www.finishing.com.
There are a few ways to kill this particular cat. I know stainless can be black oxided but the process is dangerous and the chemicals are really scary.
I think one of the chemicals inculded some form of arsinic.
On that topic I could be wrong but just read up abit about sodium dichromate. If I'm not mistaken the byproduct is Chromium that is a real hassle to get rid off don't just pour it down hole 13:p .
I looked at Black bronzing on stainless and it looks pretty good.
The best would prob be powder coating.
Check out the link above someone would be able to help you there.

hareng
03-02-2011, 10:22 AM
Agree with Westline it can be done and only know of one company that does it or did do it 16 years ago and happens to be fairly local.
Where are you Ian?

There is an alternative black chroming but just as hard to get done.

Forrest Addy
03-02-2011, 12:31 PM
Stainless is made especially to be stainless. Black is one form of stain. If you... aw hell, ferget it.

Good luck.

cuemaker
03-02-2011, 01:16 PM
I work for a company that gets request for black Teflon painted studs now and then.. Havenít done stainless in black, but have done them in many other colors.. blue and green especially...

The Teflon coating is called Xylan... It holds up pretty good..even has some corrosive protection.. But not nearly as good as cad...

RWO
03-02-2011, 03:22 PM
Brownells sells a hot salt bath blackening chemical for stainless firearms. Virtually all stainless firearms are made from 400 series stainless, so I don't know how well it works on 300 series stainless. Calling Brownells' tech support line might offer some advice.

http://www.brownells.com/.aspx/pid=1103/Product/OXYNATE_reg__NO__84___HOT_CHEMICAL_BLUING_COMPOUND

RWO

gmatov
03-03-2011, 01:12 AM
Ian,
Dissolving Sodium Nitrate, fertilizer, in Sulfuric Acid makes it into Nitric Acid.

The Sulfuric, as battery acid, will only be about 28%, so you are not going to get concentrated Nitric, but it will dissolve Silver.

I think the ratio is 1/2 cup per quart of Sulfuric Acid.

Nitric, here in the US, I asked a Compounding Pharmacy if they could make me 1 ounce of Schwerter's Solution. With the HazMat fees for a little Nitric, 70%, the one ounce would cost me 95 bucks an ounce. Probably would have been about 100 bucks a gallon, but it only lasts about 90 days before it has to be renewed, so no sense paying for that.

I wonder if I could have bought the Nitric from them and mixed it as I needed it. For the same price, as I paid to have it shipped. I'll have to go back and ask.

Cheers,

George

batt-man
03-03-2011, 03:39 AM
Ian,

I don't know if they can export to Holland but have a look at www.reagent.co.uk

They will sell to private individuals and i have in fact purchased nitric acid from them in the past.


Alternatively have a look at http://stores.ebay.co.uk/Tools-4-Jewellery-Ltd?_trksid=p4340.l2563 under their chemicals section and you can buy nitric acid from them.

Hope this helps.....

Cheers
Batt

holls
03-18-2016, 08:14 AM
Hi Batt-man, how long do these chemicals stay on the steel? Also are they safe to put on steel in the kitchen where we prepare food? Would love to have some black stainless steel.

ikdor
03-18-2016, 01:02 PM
Holy old thread, Batt-man!

akajun
03-18-2016, 04:38 PM
Have it melonited, boosts the hardness as well.
Caswell makes some cold solutions that work on 300 series, but are not that durable to rubbing.