Chemical to clean weld marks from stainless steel, or procedure to remove the burn marks?

A. I use a 70/30 mixture of concentrated nitric/fluorhidric acids for a few minutes.

Hydrofluoric acid burns

Never use HF anywhere unless trained!
If you do, you MUST have the antidote gel on hand for instant use!

Calcium Gluconate
for HF acid burns

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A. Beside the corrosive nature of the acid, the use of hydrofluoric acid in a hand operation to clean weld oxide is extremely hazardous as it is insidiously absorbed through the lungs and skin, causing permanent damage and death to internal organs.

A. From a poor mans standpoint, 50/50 hydrochloric acid is probably the quickest semi safe way to fix the problem. rinse well with warm water or it will rust later and or stain. Rubber gloves ⇦ this on eBay or Amazon [affil links] swab and rub.

Fluoride is not that unsafe when you use ammonium bifluoride to get the fluoride content. By then it is so dilute that it is no more dangerous than the nitric acid is. 70% hydrofluoric is extremely dangerous until diluted and absolutely should not be used without extreme caution and by QUALIFIED TRAINED people only.

Polishing with a 410 SS wire rotary brush is a guaranteed way to have the area rust when exposed to high humidity.

Electronic Weld Cleaner

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A. The best known way to remove heat generated discoloration off of stainless steel (any welded, laser or plasma or other heat generated method that causes it) is to use an electronic weld cleaner. Good luck and steer clear of those pastes, they are very very hazardous.

A. There are commercial products that should be available through a good welding shop for chemical removal of the oxidation around the weld. These pastes should be safe when handled carefully and supplied with directions and applicable warnings. My guess is that you will have to do some mechanical finishing to restore the original texture.

A. Brian:

There is no "easy" way to do all you want to do, primarily the returning of the finish to #4 Brushed Finish. The best system we could recommend is to brush the surface of the welded area to remove the weld discoloration and return the surface to a semblance of the #4 finish with a ss wire brush or rotating brush on a drill or similar, followed by passivation with a proprietary citric acid to make sure the surface of the weld will not rust. Let us know if we can help.

Regards,

A. Try this combination Nitric - hydrofluoric acid combination. It will take some 5 minutes when you brush the welded part with tooth brush.
Hari Om!

A. Pickle the weldments in 30% nitric, 5% hydrofluoric (rest water) at room temp for enough time to clean. You can opt for additional passivation in 30% nitric (no fluoride). Both chemicals are extremely dangerous and aggressive to all forms of life. Personnel protection, neutralization and disposal according to local laws is mandatory. Injectable calcium gluconate is also highly recommended to be available in case of possible skin contact with HF.

A. We use a product called Blueaway. It looks like runny toothpaste ... but requires very little effort. Not sure where we bought it.

Good luck,

A. Dear Pranabesh

You need to check the Welding Electrode -- what is it?

Are you using Arc Welding? -- Switch over to Gas Inert Welding.

Do not use chemicals to remove tinting of welded areas. Instead passivate them by simple grinding.

You must get in the habit of cleaning the component free from any residue of Chemical/Abrasive before selling it.

Hope this helps you.

A. Sir, looking at the photos it appears as if you have contamination, either your filler rod is not pure or the process you are using is introducing contaminates.

We use TIG welding; either fuse the weld or if you have to add filler 308L wire (wire is cleaned prior to use, as is the joint area). Straight Argon or a Argon-Helium mix is used for the shielding gas.

Make sure your heat is not too great that you draw oxygen in from the rear of the weld (or run a gas purge behind the weld). This will avoid "crystalization" of the rear of the weld.

Hope this helps.

A. Good TIG welds that are cleaned and chemically passivated afterwards will give good results. What alloy is this?

Grinding of the weld DOES NOT passivate it. Quite the opposite, it can easily cause ferrite formation that will rust later unless passivated chemically.

A. Carlos,

I have used a type of product called 'pickling paste' which is a gelled acid product. We bought it from a local weld supply house. Make sure you get a material intended for stainless steel. This product is dangerous to use if you do not follow the safety recommendations and do not use PPE (such as rubber gloves ⇦ this on eBay or Amazon [affil links] , face shield ⇦ this on eBay or Amazon [affil links] , etc.). Also, if you use this material on a large area, you may need to be concerned about proper ventilation if you use this material on a large surface area. You might want to consider mechanical methods instead, such a using abrasives or glass beading.

A. Was anticipating the same problem. Found a product called BlueAway which is supposed to remove bluing from motorcycle pipes and stainless steel. Found it after a internet search at a motor cycle parts place for 17.99/2.5oz. Haven't tried it yet but may buy some.

A. Hi Carlos,

Pickling Paste can be used and you should be able to find it at a welding supply.

Micheline Forth

A. William:

Typical weld paste for pickling of welds will remove the heat effected discoloration (heat tint) that you see. It is generally a blend of nitric and hydrofluoric acid in a gelled solution. After removal of the heat tint, passivation should be performed with either nitric or citric acid gel passivation. These solutions can be purchased from a number of suppliers.

Thanks,

A. Try The Magic Wand from Diversified Products. It cleans weld burns quick and easy to use.

A. Hi, Paulo. Yes, this generally goes by the name of 'pickling paste'. It usually involves the nasty acids hydrofluoric and nitric, so observe the MSDS carefully.

Regards,

adv.
Paulo, several appliance manufactures are using our Scratch-B-Gone kit to remove just this problem particularly at corner weld sights. Take a look.

A. Stainless wire brush right after welding.
Electropolishing will also remove heat discoloration and render the surface more corrosion resistant then passivation or pickling alone. It will also brighten the surface.

A. Hi Pritam. We appended your inquiry to an existing thread on the subject, which explains several different possible approaches. Good luck.

Regards,

A. Hi Jeff. We added your question to an existing thread about welding of 304 SS. The biggest problem is probably not how to clean the weld discoloration, but the fact that this is unlikely to be a satisfactory grill for an automobile in terms of staying attractive and rust free. If it's a show car kept in a garage and not used on the road, it's one thing; but environmental exposure on an automobile that is in use is rated "very severe" (as opposed to other applications which are rated mild, moderate, or severe). The 304 SS will probably rust even if passivated, and will surely rust if not. But good luck.

Regards,

A. Jeff,
Since you're in Canada I'm going to assume lots of salt on the road during the winter. I wouldn't try it with anything less than 316 that is electropolished and then citric passivated, and even then it would probably need occasional treatments to remove corrosion and repassivate.

Most car parts like that are chrome plated, I believe, and even then they don't often hold up forever to road conditions.

- - -

Jimmy,
I guess I'm not following you completely here. When you say acid cleaning, what type of acid? Liquid solution or some kind of gel/paste product? Acids are totally water soluble, so if your parts end up with dried acid residue on the surface it means your rinsing is not very good. Though sometimes people mistake acid etch marks for a "residue".

When you say seam leaks, what is leaking, and through what seams? The welds?

Hi John. A picture is worth a thousand words. Please send a pic to mooney@finishing.com.

Regards,

A. Akshata,
You can certainly try, but don't expect much success. Those acids generally are not powerful enough to etch heat discoloration from stainless.

A. Hi Jim. The pipes should be passivated with citric acid based passivating solution after polishing. But I think (but don't know for sure) that getting them electropolished will deter both the brown spots and the general darkening.

I doubt that what you did 32 years and several mirror polishings ago is having any effect on what is going on today.

Regards,

A. Hi again. You can apply the citric acid yourself, but I would advise buying it as a proprietary so you get the right stuff at the right concentration, as well as the necessary instructions. I can suggest contacting Stellar Solutions [a finishing.com supporting advertiser] about it.

You cannot do electropolishing yourself. You would have to send the pipes out to an electropolishing shop. Good luck.

Regards,

A. Haribabu,
Normally mechanical descaling like bead blasting or wire wheel grinding, or some sort of pickling paste.

A. Google "Pickling Paste" - Apply, let stand, rinse off.