Metal on metal rust

[mikeypj]

I know a little about galvanic something(not enough to know the name). Where the exhaust hangers are strapped around exhaust is where my exhaust is rusting/rusted through. Is the purpose to keep you paying $200+ to fix it every 5 yrs or so?

 

[o1marc]

Galvanic corrosion happens with dissimilar metals, not steel on steel. Heat and vibration is probably what got that connection.

 

[mikeypj]

So, how can it be stopped? Im considering wrapping the pipe in that fiberglass cloth and then putting the hanger over it..im guessing its going to be a $400 fix to replace the pipe from the first hanger back.

 

[family wagon]

In addition to heat and vibration there's always a little gap between the pipe and a strap-style hanger. Dust, water, and road salt get in there and accelerate the corrosion. It's hard to guess whether fiberglass wrap or other spacer between the pipe and the strap would help.

Weld-on hangers eliminate those problems above, but the welding burns off the coating (whether aluminized or galvanized) and then it's at risk of rusting again. Is that a net win over a strap-style connection? Maybe.. at least it lacks the gap that holds debris and lacks the vibration which turns a little dirt into a grinder.

I put an exhaust system on my pickup truck a few years ago which had an interesting solution: hanger hooks welded to u-bolt style clamps. The u-bolt style clamp won't vibrate the way a strap-style hanger can and welding the hanger there also avoids burning the coating off the exhaust tube.

Depending on how advanced the corrosion is on your exhaust, u-bolt clamps might not be an option. If the tube is weakened too much these would be liable to crush or even tear through your tubing.

 

[mikeypj]

In addition to heat and vibration there's always a little gap between the pipe and a strap-style hanger. Dust, water, and road salt get in there and accelerate the corrosion. It's hard to guess whether fiberglass wrap or other spacer between the pipe and the strap would help.

Weld-on hangers eliminate those problems above, but the welding burns off the coating (whether aluminized or galvanized) and then it's at risk of rusting again. Is that a net win over a strap-style connection? Maybe.. at least it lacks the gap that holds debris and lacks the vibration which turns a little dirt into a grinder.

I put an exhaust system on my pickup truck a few years ago which had an interesting solution: hanger hooks welded to u-bolt style clamps. The u-bolt style clamp won't vibrate the way a strap-style hanger can and welding the hanger there also avoids burning the coating off the exhaust tube.

Depending on how advanced the corrosion is on your exhaust, u-bolt clamps might not be an option. If the tube is weakened too much these would be liable to crush or even tear through your tubing.

I'll get some pics of it..its weird that the only rust on the pipe is where the hangers are, maybe an inch on both sides. Everywhere else looks almost new..when i replace the pipe the hangers need replaced too.

 

[Tango-SKO]

One word...stainless.

 

[mikeypj]

One word...stainless.

Assuming i can get stainless hangers. Isnt the pipe already stainless?

 

[EastCoastCB]

Assuming i can get stainless hangers. Isnt the pipe already stainless?

Its usually aluminized steel.

 

[Tango-SKO]

Don't know of ant buses that come from the factory with stainless exhaust systems.


Gotta DIY it.

 

[mikeypj]

Don't know of ant buses that come from the factory with stainless exhaust systems.


Gotta DIY it.

This exhaust is not the original..my bus is an 87.

 

[EastCoastCB]

Will a magnet stick to it? If not its likely stainless. If so its aluminized steel like 99% of the other school buses out there.

My 85, 92, 98, 99, and 2004 all appear(ed) to have the original exhausts.

 

[mikeypj]

Will a magnet stick to it? If not its likely stainless. If so its aluminized steel like 99% of the other school buses out there.

My 85, 92, 98, 99, and 2004 all appear(ed) to have the original exhausts.

If this exhaust is original its really clean, minus the rust spots..lol..either way its gotta go before we hit the road. Maybe put a cherry bomb muffler on it! Bwahahaha

 

[Captain Bill-SKO]

Stainless steel doesn't really rust and if it does its usually surface rust. Pimp that bus go titanium with a borla exhaust. HAHA but seriously if you plan on keeping the bus around for a long time think about replacing it with stainless its a bit more expensive but should be around for the life of the bus well worth the investment.

 

[o1marc]

So, how can it be stopped?

Don't put bare steel and aluminum together. Insulate somehow. I imagine your issue is not galvanic corrosion, but failure of the pipe. That hanger may hold heat at that point and with water and vibration just wore it out. Once the aluminized wore off the rust started.
4" stainless pipe runs about $12/ft. I doubt any bus company is building that into the budget. No ROI.