How to Choose a Coating for an Exhaust System

Oct 20, 2012

Naturally, for street rods, customs or restoration projects, the exhaust system needs to retain a fresh appearance, avoiding the prospect of rust at all cost. This includes the entire exhaust system, from the exhaust manifold or header to secondary pipes, mufflers and tips.

Viable options include using stainless steel material for the entire system, or having all components coated with a high-heat specialty protectant that’s usually ceramic-based.

When it comes to stainless steel, be aware that there are numerous compositions of this material, with varying levels of alloys and ferrous metals.

Remember, just because a manufacturer calls the material “stainless” doesn’t guarantee that it won’t eventually rust.

For example, Ford included “stainless steel” exhaust headers on its Mustang GTs in the late 1980s. While it sounded cool on paper, the headers quickly surface-rusted, due to a low non-ferrous alloy metallurgical formula.

Thankfully, quality performance aftermarket exhaust manufacturers tend to use high-alloy materials to prevent this.

Another popular route is to take advantage of specialty ceramic coatings offered by companies such as Jet-Hot.

The parent material is first lightly abraded (blasted) to create a “tooth” for the coating. The coating is applied under specific heat conditions, per the coater’s formula.

If the surface preparation is done properly, the coating should last for many years.

In today’s market, color and finish texture choices abound, including high-luster aluminum that looks polished to semi-gloss, matte and even flat finishes, in an array of colors.

If you ship off a component that has some age to it, there’s always the possibility that surface prep (blasting) may result in pits or pin holes if the metal was badly rusted or thin.

If you’re concerned about this, your best bet is to lightly blast the component in-house to remove existing paint and/or surface rust.

If you find any pinholes, you can weld-fill and finish. If you find visible pits, you can fill and dress them using an all-metal filler before you ship the item out for coating.

A quality ceramic coating serves another function: performance.

A ceramic coating (ideally applied both inside and outside the exhaust passages) also serves as a thermal barrier.

This captures a great deal of exhaust heat and instead of the heat dissipating through the metal (into the engine bay and undercar areas), more of the heat is captured and contained, scooting out of the system instead of radiating from the system’s surfaces.

This tends to create a more efficient scavenging effect for the exhaust, which (in theory or practice) improves exhaust efficiency, which presumably translates into increased power.

Granted, any slight performance increase via thermal barrier coatings is more of an issue in a pro race application and likely won’t be felt in a street-driven vehicle.

The potential performance issue aside, less radiated heat also means lower under-hood and under-car temperatures.