Anti-rust treatment for exhaust?

[r3g]

Firstly, before everyone rolls around laughing at the suggestion, I am of course aware of the termperatures that exhausts reach!

With that out of the way, the price of a stainless exhaust for my car would take many years to recoup vs the price of several standard crappy steel exhausts, and I'm not sure I'll own the car that long. The crappy steel ones all rust around the welds on the mid and rear silencer boxes and barely last a year before they start blowing. I was wondering if there's a high-termperate underbody seal compound that I could lard on to these areas to extend the life of the exhaust, but obviously don't want my car to erupt in a ball of flames once the engine and exhaust is up to temperature.

[Grenadier_45]

You can buy high temperature paint from the likes of Halfords. And if you can clean the welds up well enough to be able to apply it, you can slow down the rate at which that visible part of the weld corrodes on the outside of the exhaust. The fundamental problem with exhausts, though, especially on petrol engines, is that they most usually corrode from the inside out - exactly where you can't get any protection.

[dontlookdown]

As above, exhausts tend to rust from the inside out (as indeed does the rest of the car). But you can't inject cavity wax into the exhaust for obvious reasons, and anything you put on the outside is unlikely to do much good, even if it can stand the temperature.

[paintman]

As already said, exhausts usually rot from the inside out.
Burning a gallon of diesel or petrol produces a large amount of water.
This appears as steam & the liquid you see dripping out of the tailpipe.
It also condenses inside the cold exhaust & until the exhaust system gets hot enough to boil it off effectively just sits there.
Cars that only do short journeys will go through exhausts - esp the silencer boxes - much quicker than cars which are used for long journeys for that reason.
I have seen some silencers with a factory drilled small holes to try & help - and have done it myself. Usually in the end plate at the lowest point as fitted. Never had an MOT issue.

[Evoluzione]

Try some high temp paint, but any that i've had a fairly idle attempt with haven't worked. It just isn't durable enough.
It just seems to wear off, burn off or the rust come through. If it's already rusting it's too late. If it's already been painted in something which burns off it's also a waste of time.
Outside of SS, aftermarket exhausts on the whole aren't as good as the OEMs whose typically last about 10yrs in my experience.
It's down to the content of the steel, IIRC high aluminium contents are expensive, but last longer.

Edited by Evoluzione on Friday 14th October 13:28

[Belle427]

Bilt hamber do a product called atom mac which may help but hardy worth it in my opinion.

[r3g]

Thanks all. Well informed replies that I hadn't really considered, but makes total sense of course as even without the moisture in the emissions the inside of the exhaust with get condensation build up especially in the colder/wetter months. The standard Klarius exhausts on the mk1 C1s are utter garbage and you can watch them rot in real time. Not sure what else can done short of going stainless.

[Smint]

I sprayed mine with Zinc paint in situ, probably Bilt Hambers but could be someone elses product, it don't look pretty but it hasn't burned off and shows little deterioration after 5 years, thats on a Diesel without a DPF regen to worry about.

[steveo3002]

ive had ok results with screwfix zinc spray , and taking the car on a decent run when ever possible