Rusted stainless exhaust tubing - not used

[timsch]

I bought some 304 stainless exhaust tubing for a project that hasn't happened yet. It had an oil coating on it, but got wet in a flood and rust started showing in areas. Time passed and now the majority of the surfaces have rusted. I did repassivate a piece of it and it looked good for a while (although never good as new), but that has started rusting again.

Is there any saving these pieces, or are they scrap at this point?

 

[Firebrick43]

I bought some 304 stainless exhaust tubing for a project that hasn't happened yet. It had an oil coating on it, but got wet in a flood and rust started showing in areas. Time passed and now the majority of the surfaces have rusted. I did repassivate a piece of it and it looked good for a while (although never good as new), but that has started rusting again.

Is there any saving these pieces, or are they scrap at this point?

I would say its not 304 if you passivated it with nitric acid to remove all the free iron and it still rusted. Lots of amazon stuff listed as 304 stainless is a lie and actually not 304 at all.

 

[timsch]

I used citric acid wit fumed selica for the passivation, not nitric acid.

Well, it was from Amazon.... Looks like I may have been had.

 

[DocsMachine]

Try a magnet. 304 is just barely magnetic to a powerful magnet- basically nonmagnetic.

If it sticks firmly, it ain't 304.

Doc.

 

[Bert_]

Scrap? I mean it's still a piece of pipe and will serve it's intended purpose, even if it's not "shiny"

 

[timsch]

Well, I did buy it to be shiny.

I'm sure I'd have a hard time getting rid of it given that I keep so much that others would trash. If I did get rid of it, it'd just be for the shame of buying something that is counterfeit even though I should have known better.

That being said, I was aware that it's a gamble when ordering from Amazon on something like this. I did check it with a magnet when I received it, and it passed that test.

 

[sqznby]

Passed meaning the magnet stuck to it? I find that hard to believe if the tubing is covered in rust.
Is this for a personal project or is it for a paying customer?

 

[timsch]

Passed meaning the magnet stuck to it? I find that hard to believe if the tubing is covered in rust.
Is this for a personal project or is it for a paying customer?

Magnet did not stick. Personal project.

However, I just went and checked with a much stronger magnet, and it did attract strongly. So...I've been had. Too bad because I used this same tubing for a "stainless" exhaust on one of my cars. Penny wise, pound foolish.

 

[dscheidt]

Magnet did not stick. Personal project.

However, I just went and checked with a much stronger magnet, and it did attract strongly. So...I've been had. Too bad because I used this same tubing for a "stainless" exhaust on one of my cars. Penny wise, pound foolish.

304 becomes more magnetic when worked cold. It’s not unusual for drawn tubing to be magnetic, especially where it has been bent. That said, there’s lot of Chinese stuff that doesn’t have enough nickel to meet the specs. It’s still more rust resistant than mild steel.

 

[timsch]

I don't know where I checked it when I received it. I must have made a poor choice of magnet that time. It may be more resistant, but looking at it now, it doesn't matter. It's not just a bit of minor surface rust that you see if you look closely. It's solid at this point in most areas.