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Very high temperature coatings for manifolds and exhausts

Silicone and ceramic coatings for manifolds, downpipes and exhausts: what the ratings mean, why the heat cure is not optional, and when to send the part away.

Updated 2026-10-14

On this page
  1. Why enamel won't do
  2. Reading the ratings
  3. The cure is part of the job
  4. Send it away or spray it yourself
  5. Where people go wrong
  6. Sources
  • Engine enamel tops out at 300°C. Manifold coatings start at about 650°C. They are different products.
  • The coating stays soft until it has been through a staged heat cure. Most failures are skipped cures.
  • VHT says FlameProof will not bond to stainless. U-POL lists stainless as a surface its Raptor Flameproof goes straight onto. Read the sheet for the can.
  • Only a sprayed ceramic barrier, applied by a coating firm, makes the engine bay cooler.

Why enamel won't do

The numbers make the case. Hycote rates the best colours in its engine enamel range at 300°C and its gloss black at 140°C. VHT rates FlameProof, its header coating, at 1,300°F to 2,000°F, which is 704°C to 1,093°C. POR-15 rates its High Temp coating at 1,200°F, about 650°C. Nothing sold as engine enamel reaches the bottom of that band.

Two different things are sold for this job. One is an aerosol or brush-on coating you apply at home. The other is a service: the part goes away, gets grit blasted and comes back coated. Zircotec in Abingdon applies its ceramic by plasma spray. The coating material is melted in an electric arc that the company puts at around 10,000°C and thrown at the part, leaving a layer about 0.3 mm thick.

Reading the ratings

Read the qualifier before the figure.

VHT's 704°C to 1,093°C is given as intermittent, and it is a range. A range covers a family of colours and conditions. It doesn't promise anything about the can in your hand. POR-15 gives one figure, 1,200°F, and converts it to 648.8°C, a precision no exhaust will respect.

Zircotec's figures describe service temperature instead of a peak. Its coloured finishes are listed for use up to 900°C. It also publishes what the coating does as well as what it survives: surface temperatures down by about a third, and under-bonnet temperatures down by more than 50°C.

Those are different claims. An aerosol rating tells you the film won't burn off. A barrier figure tells you the heat is staying in the pipe. If the aim is a cooler engine bay, only the second one counts.

The cure is part of the job

Most exhaust coatings that fail were never cured.

VHT FlameProof doesn't reach its properties by drying. Once dry it has to be cured. Off the car, that means three stages with cooling between them: 121°C for 30 minutes, cool for 30; 204°C for 30 minutes, cool for 30; then 343°C for 30 minutes. On the car, VHT gives an idle sequence: idle for 10 minutes and cool for 20, idle for 20 and cool for 20, then drive normally for 30.

POR-15 High Temp works the same way. The brush grade wants 24 hours on the surface, then 15 to 30 minutes above 150°C to cure fully. The aerosol is stricter and needs at least two hours at 205°C, which is an oven job.

An uncured film looks finished. It is soft, it marks under a fingernail, and solvent lifts it straight off. If you plan to fit the manifold and leave the car in the garage until spring, cure it in the oven first.

Send it away or spray it yourself

A coating service starts from bare metal. Zircotec grit blasts every part as the first step of its process, so nothing you did beforehand survives, and the coating can't go over old paint. It covers most metals, and the company names stainless steel, mild steel, cast iron, aluminium and titanium. You get a thermal barrier as well as a finish.

An aerosol is a weekend job, and it has a limit the service doesn't. VHT says plainly that FlameProof will not bond well to stainless pipes, and that aluminised and galvanised pipes must be sand blasted and cleaned first. If your system is stainless, FlameProof is the wrong can and preparation won't change that. U-POL's data sheet for Raptor Flameproof lists stainless steel, galvanised steel, aluminium and titanium as surfaces it goes straight onto, so the answer depends on the maker, and the sheet for the can in your hand is the one that counts.

Where people go wrong

Engine enamel on a manifold is the classic. The gap between a 300°C enamel and a 650°C coating is too wide for any judgement call.

Primer catches people out because two makers give opposite instructions. VHT wants its own SP100 FlameProof primer underneath. POR-15 High Temp goes straight onto clean, prepared metal, needs no primer or topcoat, and is stated as incompatible with any other primer. Follow the tin you bought. There is more under primers.

And don't prepare a part you are sending for coating. They will blast it again anyway.

See every very high temperature coating in the shop.

Sources

In the shop

All 65 very high temperature coatings