New exhaust has surface rust?

[UVB76]

Hey all.

Picked up a new 3" exhaust last week, aluminised mild steel, nothing fancy just wanted to replace the factory exhaust because it's pretty beat.
Inside the new exhaust pipes there's some surface rust along a seam running the length of the pipes. I'm wondering if this is normal or a sign of a defective product? I've attached some pics and would appreciate advice. It's the first exhaust I've bought so not sure if this is to be expected.

Cheers all.

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[mudnut]

I would say it has been sitting around for a very long time. I would also expect that flange to have a complete weld around the pipe.

[4bye4]

I deal with replacement exhausts at my workshop here all the time, and what that appears to be is just where they have heated it during manufacture cooling and picking up moisture causing a bit of surface rust. That can happen in a day. Having said that, it doesn't take a second to spray these things with protector, even WD40 during manufacture. Depends on the quality of workmanship you like to portray I guess. Summare - probably ok product to use but sloppy manufacturer.

[UVB76]

I would say it has been sitting around for a very long time.

Yeah, that's my thought, too - it's been sitting for a while in the warehouse.

I would also expect that flange to have a complete weld around the pipe.

Good point - the 3rd pic doesn't show it but there's a full weld of the flange on the inside of the pipe. The other flanges are welded on the outside of the pipe so not sure why this one's different.

Even though it was a cheaper exhaust, things like this ^ don't give me much confidence about the overall quality.

I deal with replacement exhausts at my workshop here all the time, and what that appears to be is just where they have heated it during manufacture cooling and picking up moisture causing a bit of surface rust. That can happen in a day. Having said that, it doesn't take a second to spray these things with protector, even WD40 during manufacture. Depends on the quality of workmanship you like to portray I guess. Summare - probably ok product to use but sloppy manufacturer.

Good to know about the moisture after manufacture.
The inside of the exhaust has a residue, oily feel to it, so I suspect something has been applied - doesn't have a smell, though. It's only surface rust from what I can see so I'm not heaps worried, but it does make me question how the welds will hold up, rust around the welds, etc.

[UVB76]

What do you reckon if I sprayed some Penetrol on the surface rust areas, and around the welds? Would this cause a problem when heating up or with the aluminised mild steel?

[threedogs]

Hit it with a wire brush and spray with HT paint
Once fitted soot will take care of the inside
Not sure why its not fully welded but an exhaust shop
can weld that up for you if you feel it should

[4bye4]

What do you reckon if I sprayed some Penetrol on the surface rust areas, and around the welds? Would this cause a problem when heating up or with the aluminised mild steel?

I wouldn't worry about it, especially on the inside. Penetrol will only burn off anyway. Spray the nuts and bolts with Penetrol about an hour before you want to undo them. Spray the outside after you have fitted it with HT paint as suggested by TD's.
The welding is probably just a couple of tacks to hold the flange in position while the main weld was done, assuming it is welded on the other side of the flange.

[Sir Roofy]

Yeah, that's my thought, too - it's been sitting for a while in the warehouse.


Good point - the 3rd pic doesn't show it but there's a full weld of the flange on the inside of the pipe. The other flanges are welded on the outside of the pipe so not sure why this one's different.

Even though it was a cheaper exhaust, things like this ^ don't give me much confidence about the overall quality.


Good to know about the moisture after manufacture.
The inside of the exhaust has a residue, oily feel to it, so I suspect something has been applied - doesn't have a smell, though. It's only surface rust from what I can see so I'm not heaps worried, but it does make me question how the welds will hold up, rust around the welds, etc.

If your worried about it take it back and show them and exchange it

[threedogs]

I wouldn't worry about it, especially on the inside. Penetrol will only burn off anyway. Spray the nuts and bolts with Penetrol about an hour before you want to undo them. Spray the outside after you have fitted it with HT paint as suggested by TD's.
The welding is probably just a couple of tacks to hold the flange in position while the main weld was done, assuming it is welded on the other side of the flange.

would you recommend applying some "never seize" or similar to the bolts closer to the motor

[4bye4]

would you recommend applying some "never seize" or similar to the bolts closer to the motor

I never have bothered mainly because the temps in an exhaust will burn off just about anything you can apply when assembling. May as well just give them a good soak with penetrine or similay before removing. Really difficult stuff in the workshop we have sprayed then heated with a heat gun then sprayed again. A good thing to have for this job IMO is a metrinch set as the bolts on exhausts are often rounded or rusted. If all else fails buy a nut splitter. Works better than the hair splitter on the other thread.