Hi there

We have just bought new steel heat exchangers and have heard that some people advocate ceramic coating - was wondering what the advice or comments were on whether to do this?

Thanks

Brian

Ceramic is an insulator... If you want the heat exchangers to actually work as heat exchangers, you don't want to coat them. Most certainly not on the inside. And if you coat the outside, you will be trapping more heat in the steel than is really best for it. There will be accelerated metal fatigue if you overheat the steel.

If it were headers, then I'd say go for it. But HX's? You'll be wasting more than just the money spent on the coating...

-Josh

Sorry thats nothing more than spreading internet FUD!
Ceramic is an insulator, DUH.
Have you ever had a pair of HE coated? I have...
The point of HE's IS to trap then circulate air around the hot exhaust tubes.
The more heat you can contain in the clamshell the better your heating system can work.
Im not even sure how you would coat the insides of the clamshells w/o mechanically removing & reattaching them
Accelerated metal fatigue BUWHAAAHAHAHHHAHAha, Get real !

I had mine coated years ago by JetHot, and they seem to be holding up great and work well. If the heat exchangers are SSI, probably not needed, but I was coating original 914-6 exchangers that were difficult and expensive to replace.

I bought an NOS system (HE and muffler) from Gerold (thanks!) and had them ceramic coated. We tried to match the original color but only got close

Let me know if you want to see some pics.

Cheers

yes please


cjl

Pictures? Was that a trick question? Of course we want to see the pictures.

Depends on if it's regular mild steel or stainless. The poster said steel, not stainless steel. Stainless can handle more than mild steel. Mild steel will likley soften and oxidize easier with elevated temperatures.

I wasn't referring to the insides of the clamshells, I was referring to the insides of the pipes, and yes the insides of the pipes can in fact be coated. I've had it done it to headers in the past.

-Josh

And if we really want to get picky... Stainless steel is a cr*ppy thermal conductor compared to regular steel. By about a factor of 4 depending on the alloy. From a heat exchange standpoint, SS is a poor choice of material. And the emissivity of stainless is also much lower than that of oxidized steel (which is what you find inside a regular steel heat exchanger once it's seen heat and water vapor...).

From a longevity standpoint, stainless is a great choice as it's far less prone to oxidation and softening. Ceramic coating the outside of SS HX's won't ruin them, but won't really improve them dramatically either since the interior SS is still a poor thermal conductor with relatively low emissivity... Nor will it do much to extend the lifetime of them either.

For a performance header, I say ceramic coat EVERYTHING. You -want- the gasses in there to stay as hot as possible for as long as possible. Hotter gasses are faster gasses. So you want to pipes to have as poor a thermal conductivity as possible.

For a heat exchanger, you want the gas to cool rapidly as it goes through the pipes so you can warm your feet and defrost your windshield as one would expect. So there you want high thermal conductivity and high emissivity.

Does that mean SS heat exchangers are a waste of money? Not at all! Since the regular steel HX's rust away, and at best fall apart, at worst pose health risks from exhaust leaking into the HX's, the trade-off is a pretty easy one to make. A little less efficient, but with increased longevity.

But not everything gets better with stainless steel, and modern materials are not always best for all applications.

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Tangential story... My favorite example was some company selling titanium brake pad backing plates to replace stainless steel ones... Pure snake oil that costs lots of money... One reason stainless is such a good material of choice for brake pad backing plates is the very reason why it's not a great heat exchanger material. Titanium on the other hand, with higher thermal conductivity will allow that heat to get to the brake piston heating it up faster and pushing the brake fluid to overheat sooner. So much for fancy expensive titanium backing plates...

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-Josh2