Joe Diemer

Topic: Polishing Stainless Without the EPA Possible?

Hello Finishing Talk Members,

I manufacture custom birdcages for the exotic bird market. In the past I've used mild steel and finished by bead blasting and then powdercoating. I'd like to offer the product in stainless, but cannot find an appropriate inhouse finishing system to remove the oxides from the brazing process.

These cages are large - the size of an 85 gallon drum and larger, and have hundreds of cross-wire welds. So obviously hand polishing is out. Bead blasting the joints leaves a satin finish that is too time consuming to polish. They are too large to tumble. An immersion process would be the way to go, but ultrasonics in citric acid only removes about 50 - 60 % of the oxides.

Electropolishing seems perfect, but I'd like to avoid serious mineral acids like hydrofluoric and nitric due to the sheer amount necessary, and the desire to keep the EPA and board of health away from our shop. Looks like we've hit a brick wall! Any ideas, info, or websites to check out would sure be appreciated!



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skip

Re: Polishing Stainless Without the EPA Possible?

Joe Diemer, From my previous post. I don't think the EPA knows or even cares about this inhouse process used in the welding department.

Hatco Foodmachine Company in Sturgeon Bay-factory/Milwaukee-office cleans weld stain and smoke from stainless steel weldments of welded cross wires and folded cornor joints to produce drip pans for food warmers with an acid compound that I have no knowledge of. But watched this being done.

Using a wood tounge depressor and a wire down it's length from a transformer and buried in a piece of cotton rag...this cotton is dipped into a cap full of solution and placed on the stain. Moments later the stain is gone and the area is spounged with warm water padded dry.

So dab on the acid, asap touch the stain with the wand and presto. Weld stain on the stainless steel is gone.

The gals doing the job just use rubber gloves, and an splash plastic apron and safety glasses. No respirator required. After the touch the area is padded dry.

Maybe something can be made out of that. I wish I could be more help.

skip.

Last edited by skip (12/23/2009 - 01:21 PM)

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DustinGebhardt

Re: Polishing Stainless Without the EPA Possible?

I know of a shop that uses the same principal that Skip describes, but on a much larger scale. Electropolishing can be done with a wand, especially when all you want is the clear up the weld stain. Most e-polishes uses some sort of acid and perhaps peroxide, but tend to be much more user (and EPA) friendly than non-electrical chemical polishes. Contact your local metal finishing vendor for more info. If you are in the USA, I can send you some contact info for some top-notch metal finishing supplies vendor.

-Dustin Gebhardt,
CEF
Plating Engineer
Danaher Tool Group
Gastonia, NC

Joe Diemer

Re: Polishing Stainless Without the EPA Possible?

Hey guys, thanks for the replies. Skip, you're probably right about the EPA knowing or caring about my operation - I might have been flattering myself. The magic wand method sounds interesting, but I'm going to keep pursuing an immersion method due to the quantity and geometry of the joints.

I'm trying to remove gooey flux residue, black braze oxides, and mild heat tint. The citric acid in ultrasonics removed all but some of the oxides, and left a "frost" wherever flux was.

Just for kicks I gave some samples to the big local finisher here in Portland Oregon to see what the heavy duty acids could do. They came back in bad shape. More of the braze oxides were removed (80%), but all of the 304L was greyed. The silver braze alloy was dead grey also. Strangely the 316L looked great, except it too was greyed where the flux had been.

I'm surprised that I continue getting samples returned that are obviously unusable. There must be some dipping process for a reasonable cleaning of silver brazed stainless steel. I'm still trying to avoid the large vats of steaming acids if possible - seeing as how this is a family business and a couple of our members tend to be experimental.

I've been getting info on electropolishing, but they never say just what exactly the electrolytic solution is composed of. They do mention Nitric in the pre and post cleaning tho, but I hope there's another way.

Hey Dustin, I'll take that info on your vendor. Thanks for your help.

Our shop address is:

408 SE 6th Ave
Portland, OR 97214

Joe Diemer

Re: Polishing Stainless Without the EPA Possible?

Here's an update:

The vendor didn't work out. He said:

"Honestly I don't know of anyone that can help you on that type of budget (10 - 40K). As I mentioned we specialize in small companies while all of our competitors will not deal with you unless you commit to spend $250K or more with them."

I had samples electropolished at two different places and they both came back with the silver solder dead grey. So if anybody knows of a dipping process for a reasonable polishing (or at least cleaning) of silver brazed stainless steel let me know. Thanks in advance...