Welding polished 304SS tubing

A while back it seems like I remember a post about a way to remove the blue and gold colors around the weld. does anyone else remember this? what was it?

two ways work- mechanically, I use scotchbrite pads or belts on various sanders. A variable speed 4 1/2" grinder with a scotchbrite pad is nice, as you can slow it down enough that you dont get it hot and discolored again.
or- chemically.
I use a small dc power supply, mine is made for this and its 30volts, along with wand that is wrapped in fiberglas cloth, then dipped in citric acid.
There are also small bottles of acid cleaner you can buy - I sometimes use a nitric or phosphoric acid based spray on stainless cleaner you buy at the auto parts store.

Ries said:

two ways work- mechanically, I use scotchbrite pads or belts on various sanders. A variable speed 4 1/2" grinder with a scotchbrite pad is nice, as you can slow it down enough that you dont get it hot and discolored again.
or- chemically.
I use a small dc power supply, mine is made for this and its 30volts, along with wand that is wrapped in fiberglas cloth, then dipped in citric acid.
There are also small bottles of acid cleaner you can buy - I sometimes use a nitric or phosphoric acid based spray on stainless cleaner you buy at the auto parts store.

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Who sells the power supply? How fast does it work? We have 100s of parts to do.

Not sure if you guys can get it but we used to have a tank with diluted hydrofluoric acid that we would dump baskets of s/s parts into, remove, rinse and pressure clean. Pretty nasty stuff but it worked well.

Have since progressed to the "weld clean" electro brush at new site for doing pipework and fabricated parts during maintenance but would be a PITA for doing lots of small parts in a production environment.

My memory may be faulty but years ago I seem to remember using Tidy Bowl to remove the discoloration?

Years ago I talked to a guy on a plane that did a lot of the stainless tubular truck steps. They got the stock covered and bent and welded then mechanically buffed them, never uncovering the tube except where welded

moonlight machine said:

Who sells the power supply? How fast does it work? We have 100s of parts to do.

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There are several people selling them. The best ones are expensive- high quality german made, with cleverly thought out consumables. Walter Surfox machines- Walter 54D045 Surfox Turbo – weldingoutfitter.com

Surfox – Walter Surface Technologies

there used to be a couple of small us companies that made basic 30 volt rectifiers and sold kits, but both have gone out of business. The europeans are the main suppliers nowadays
Cougartron InoxPower - Weld Cleaning Machine for Stainless Steel


these guys are a good source for the chemicals. Stellar Solutions - Stainless Steel Passivation

I have a Cougartron unit. They work very fast.

Yeah, its pretty quick- You hit each weld, all the way around, and its a minute or so, then you rinse. Finished. If you have hundreds, portable electropolishing is totally the way to go. We do it on job sites after site welds, and have things that have been out there for 20 years in the elements, and are still fine.

crazygoat said:

My memory may be faulty but years ago I seem to remember using Tidy Bowl to remove the discoloration?

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It'll work, but many porcelain cleaners are HCL which is bad for 304 if not completely removed or neutralized.

Lot of WC cleaners are phosphoric, I’m told coke has it in too,
But as I learned the hard way it matters not a bit what the acid is called, just how bloody strong it is ( noting HF,s affinity with calcium, it has a well deserved bad rep, we had to legally keep antidote gel in the lab, you don’t want that stuff on you)
I’m going to try Ries 30v and citric, might be useful
Mark

Ries said:

Yeah, its pretty quick- You hit each weld, all the way around, and its a minute or so, then you rinse. Finished. If you have hundreds, portable electropolishing is totally the way to go. We do it on job sites after site welds, and have things that have been out there for 20 years in the elements, and are still fine.

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Please tell me all about electro polishing, I've heard of it but know nothing about it.

moonlight machine said:

Please tell me all about electro polishing, I've heard of it but know nothing about it.

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I get all my paying jobs in stainless (which has been something like 30 tons worth over the last 25 years) commercially electropolished. The guys I use have a 4' x 4' x 8' tank of heated acid, and a 1000 amp power supply the size of a fridge. They use some secret acid, but I think its mostly phosphoric. They also have a gigantically expensive underground catchwater basin for environmental impact reasons- another reason I send it out.
I often do heavily forged, as well as machined and welded, stainless work, and it can spend as much as a half hour in the tank.
But when it comes out, its shiny, consistent looking, and very clean- no rust will pop up. I have projects in outdoor public places for 20 years now that still look great, and just get pressure washed every year or two.

The downside is that, nationally, there arent very many commercial electropolishers. And some are very expensive. My guys are actually a boat railing manufacturer, so they have it for in-house use, and outside sales are gravy.
Althought lately they have been making big bank electropolishing equipment for the marijuana industry, which has been doing a lot of edibles and oils that are basically like distilling, in terms of big stainless vats and vessels that need to be sanitary.

The small scale site work you would do with a Cougartron or Walter unit is electropolishing too- you are using what is essentially reverse plating- the flow of electricity is peeling off the top layer of molecules, rather than adding a plating layer. The acid helps loosen everything up, the electricty pulls it free.

Again, chemically is always faster and easier than mechanically.

Have you tried Jenolite? We used it when HSS got a bit blue from grinding, worked a treat.

I will disagree that electropolishers are few and far between. Lots of medical device stuff is run through EP. Those machines tend to be rather small, but I have a place in town that does much larger things, like my 3'x8' railing sections I made. If you are having a hard time finding them start calling plating shops in the area. They may either do it or know who does. I used one shop at first that was not very good frankly, and it seemed like they didn't want to do it but they referred me to another shop which is the one I used for everything from there on out (per above). They are both in the Twin Cities metro. I know of others locally as well for small medical stuff, but they won't be handling railings.... Not local for the OP but I can provide references if you want. But first start looking locally, IMO.