[Formulajones]

I've had the Pypes Stainless transverse system on my bird for I guess 8-10 years now. I drive it daily. Still looks like the day it was installed. No rust problems. Of course I live in Arizona with dew points and humidity levels in the single digits where things don't really rust.

On a side note, I've had aluminized exhaust on my Chevelle for I guess 30 years now, and it was with me in Ohio before I moved to Arizona 12 years ago. It was never driven in inclement weather when in Ohio, but still subject to the moisture and humidity there. After 30 years even that system shows no sign of rust or corrosion anyplace. The aluminized coatings hold up pretty well from my experiences. But some of the stainless systems like Pypes are so cheap compared to other stainless systems, it just makes sense to go that direction.

[NeighborsComplaint]

Originally Posted by R68GTO

Aluminized exhaust is basically standard cold rolled steel with some aluminum mixed in for corrosion resistance.

Metallugically impossible. Aluminum and steel do not bond and are not alloyable. An aluminized exhaust is fabricated from standard mild steel tubing that is hot dipped in aluminum after fabrication. Scratch or weld through the coating and it will rust like any mild steel. The aluminum does not stick to the steel, it sticks to a thin silicon coating applied to the steel which in turn sticks to the steel.

[KenB]

During my work with a leading stainless supplier in US, they alway reminded people that it was stainLESS steel, not stain free. Under the right temperature and humidity conditions, plus say road salt, a thin surface red rust can form in hours., particularly on the 4xx series (ferritic) grades. And not just in a lab😀

Most of time, ferritic meets the need, though the grade chosen by an OE varies depending where in the exhaust (hot end gets “better” grades) the component is located.

[HWYSTR455]

Headers, Exhaust, and Mufflers are wear items. If you drive the car regularly, they will need to be replaced at intervals. Nothing lasts forever. Deal with it is what I say.



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[Geoff]

I have used 409 grade s/steel on many exh systems. It will discolour, but does not rust.

[Shiny]

Originally Posted by KenB

During my work with a leading stainless supplier in US, they alway reminded people that it was stainLESS steel, not stain free. Under the right temperature and humidity conditions, plus say road salt, a thin surface red rust can form in hours., particularly on the 4xx series (ferritic) grades. And not just in a lab😀

Most of time, ferritic meets the need, though the grade chosen by an OE varies depending where in the exhaust (hot end gets “better” grades) the component is located.

As I recall, a chemical process called "passivation" is used to stabilize the naturally-protective oxide films that make stainless stainless. I think this is common on machined parts that can have contaminant particles embedded but is also used on "cosmetic" applications like appliances.

Do you know if tubing used for exhaust would be treated this way and how well it might prevent rusting?

I expect exhaust tubing is made from alloys at the "low" end for chromium content (low cost stainless). This might make them even more susceptible to corrosion than other 400-series alloys.