Descaling and passivating SS

Couldn't seem to find anything that directly addressed this issue on
Google. So maybe somebody here can advise me.
I'm making small items of stainless steel for costume accessories. I
have to heat the square steel and twist it tightly then form it into
circles. The heating of course causes scaling even though the forge is
adjusted to a reducing atmosphere.
This scale is tough! It doesn't come off easily. Tumbling the items
didn't work well idea because my tumbler has been used for years to
descale ordinary carbon steel and is throughly contaminated with steel
dust and crud. The last time I tried tumbling SS in it, the stainless
rusted worse than the mild steel afterward. Not sure whether a
post-tumbling acid bath would have prevented that or not.
Oh, the medium in that tumbler is steel scrap, which certainly isn't
making the situation better.
So I'm asking: What's the best way to remove forge scale and passivate
to make sure the SS items don't develop rust blemishes afterward from
iron contamination?
Help me, Obi Wans, you're my only hope! :)
Reply to
John Husvar
Loading thread data ...
First thing is not to do this in the forge so you can control the atmosphere better. Oh, sorry, that is the point of doing the parts.
The key to non rusting SS is to not contaminate it with regular steel parts, then get a good passivation when you are done. Your tumbling operation is exactly the wrong thing to do as far as contamination, it is making it 10x worse. I've seen SS parts that will show rusty scrape marks after 12 months that were caused by laying the parts down on a steel workbench. You need a tumbler or vibrator with a plastic liner and ceramic media that is reserved for SS only.
You also need a much stronger passivation bath than you are currently using. I don't have the specs handy but the full monte passivation uses 30% nitric acid with one of the chromates added for extra zip. Hopefully you can use one of the weaker solutions since the latter is really nasty to use and dispose of.
John Husvar wrote:
Reply to
RoyJ
I googled up some info Ernie had posted several years ago.
formatting link
I ordered the powder citric acid but haven't had the chance to use it. 3 lbs - 35.00 with shipping and instructions on how to make a wand for use with your welder to apply the acid. I don't have the company name right now but I think it is Citrisurf ****. It is in the posts. Steve Steve
Reply to
Up North
In article , John Husvar wrote:
UTP Pickling/Passivation paste is a very strong Nitric/Hydrofluoric acid paste that will easily devour the nickel and chromium oxides.
It is available at many welding supply stores.
Here is a page for Avesta's version of the stuff
formatting link

It is also the most dangerous, toxic and downright EVIL stuff I have ever had to use.
The Citric Acid/Electricity combination for electro-passivation would likely also work, but it would be slower for heavy oxides.
formatting link
Reply to
Ernie Leimkuhler
Give it away to someone who is doing it professionally. And if you want to do it at home, read the sticker on the can *carefully*. If you read "HF" (chances are very high) you should better return it or read carefully how bad HF is to your health. It simply is the most nastiest acid. One drop is enough.
Nick
Reply to
Nick Mueller
Thank you very much, Gentlemen.
I think I'll try the citric acid treatment.
The nitric/hydrofluoric etc. treatments would present too great a disposal issue for my backyard smithy. Using them safely would be no problem, but I don't think the sewer district folks would like that stuff in their treatment plant.
Those pickles might get me into one.:)
Reply to
John Husvar
Thanks for the reminder, Nick.
I do know about HF, having used it to etch glass. (in a high school chemistry class the first time!) One really doesn't want to make even one mistake with that stuff! Truly nasty.
Reply to
John Husvar
In article , John Husvar wrote:
Ernie's favorite method (which comes up in a google groups advanced groups search [ passivation group:sci.engr.joining.welding ]) is some sort of electro-passivation using a commercial product that's citric acid based.
Here's his post from Feb 23, 2003:
Reply to
Ecnerwal
THIS IS MOST IMPORTANT!
I spotted this :
No doubt. However - the Hydrofluoric acid will dissolve your body joints.
You will not have any cartledge in the fingers.... scratchy painful movement.
Please be sure to read any and all instructions and take care. This stuff zips through skin.
It etches glass and will etch you!
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Life; NRA LOH & Endowment Member, Golden Eagle, Patriot"s Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member.
formatting link

Ernie Leimkuhler wrote:
Reply to
Martin H. Eastburn

Site Timeline

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.