Exhaust Wrap vs Ceramic Coating
Heat wrap looks like the cheap answer to exhaust heat. Here is what it actually does to the exhaust underneath it, and why we do not recommend wrapping a coated system.
Exhaust wrap and exhaust ceramic coating are trying to solve the same problem: keeping heat inside the exhaust gas stream and out of the engine bay. They go about it in very different ways, and only one of them leaves the exhaust in better condition than it found it.
What exhaust wrap does
Heat wrap is a woven fibre tape wound around the outside of a manifold, header or downpipe and held with clips or ties. It insulates, so it holds heat in the pipe and reduces what radiates out into the engine bay. That part works, and it is why wrap is popular: it is cheap, it is available from any motor factor, and it can be fitted at home in an afternoon.
The problem is not what wrap does to the heat. It is what it does to the metal.
Why we do not recommend wrapping an exhaust
A coated manifold allows a certain level of airflow around the exhaust, which aids cooling and lets the coating flex with each heat cycle. Wrap removes that airflow, and it starts a cycle that works against the exhaust every time the engine is run.
- The binders start to break downWith each heat cycle, the binders in the heat wrap begin to decompose, producing water vapour while the wrap becomes increasingly porous and absorbent. This is known as binder pyrolysis.
- The wrap tightens and tearsThe material swells, which tightens the wrap around the exhaust and worsens micro-tears in the fabric. That enhances capillary action, so more moisture is held tightly against the exhaust rather than being allowed to escape.
- Corrosive agents formEach time the wrap is heated, ions migrate to the fibre surfaces and react with that moisture to generate sodium and calcium hydroxide, both alkaline corrosive agents.
- The cooling phase concentrates themWhen the engine is switched off, moisture accumulates and those agents create high pH alkaline electrolytes. On restarting, some water evaporates and leaves behind a highly alkaline residue, similar to that found in certain batteries or fuel cells.
- And then it repeatsThe cycle continues and progressively accelerates the rate of deterioration.
The end result is pitting and holes in mild steels, and weld cracks and fractures in stainless steels. The exhaust fails from the outside in, under a wrap that looks like it is protecting it.
Wrapping over a ceramic coating is worse, not safer
It is a common assumption that a coated exhaust can safely be wrapped for extra insulation. It cannot. When wrap is applied over a coating, the trapped heat creates a difference between the temperature distribution and the thermal expansion behaviour of the ceramic coating, a material expansion mismatch. That leads to the coating cracking, micro-tearing, delaminating or flaking.
Once the coating is broken, alkaline corrosion spreads underneath it, and the exhaust is destroyed from beneath a surface that still looks intact.
How ceramic coating handles the same problem
A ceramic exhaust coating is a thin film bonded to the metal rather than wound around it. Because it is part of the surface, there is no fabric to absorb moisture, nothing to swell or tighten, and no cavity for an electrolyte to sit in. The pipe still gets airflow around it.
We coat exhausts internally as well as externally. An internal coating adds a hard, smooth surface that helps the evacuation of exhaust gas, and combined with an external coating it gives the most complete heat management result. Externally, the coating also protects against corrosion, oxidation and discolouration, so the exhaust is protected rather than slowly attacked.
| Exhaust heat wrap | Ceramic coating | |
|---|---|---|
| How it is applied | Wound around the outside of the pipe and clipped or tied | Bonded to the metal as a thin film, inside and out |
| Effect on the exhaust | Traps moisture against the metal and generates alkaline corrosive agents with every heat cycle | Protects against corrosion, oxidation and discolouration |
| Airflow around the pipe | Removed | Retained |
| Internal surfaces | Untreated | Can be coated to aid gas evacuation |
| Typical failure | Pitting and holes in mild steel, weld cracks and fractures in stainless | Engineered for the thermal cycling exhausts endure |
| Appearance over time | Discolours, frays and stains | Available from hard-wearing matt through to a chrome-like polished finish |
If your goal is lower under-bonnet temperatures
Coating the exhaust is the first step, but it is not the only one. Where under-bonnet heat is the real problem, we recommend heat shields, which can themselves be ceramic coated to manage the heat, along with increasing airflow around the engine bay or adding additional vents where possible. Heat jackets are also a good option for turbos and similar components.
That combination deals with the heat without putting a moisture trap around the exhaust.
Already wrapped, and thinking about coating
If an exhaust has been wrapped for a while, it is worth having a proper look at the condition of the metal underneath before spending anything on a finish. Pitting, weld cracks and thin spots are common, and a coating applied over compromised metal will not save a pipe that is already failing. Send it in or bring it to either depot and we will tell you honestly what we find.
Ceramic coating is part of our wider motorsport coating and performance coatings work, and the underlying coating data is on our technical information page.
Exhaust wrap questions
Can I wrap my coated exhaust?
Does exhaust wrap damage the exhaust?
Is ceramic coating better than exhaust wrap?
What else can I do to reduce under-bonnet temperatures?
Can you coat the inside of an exhaust as well as the outside?
Can you coat an exhaust that has already been wrapped?
Get an exhaust ceramic coating quote
Tell us the vehicle, the parts and how the car is used, and we will confirm the right coating specification and finish.