Heat-Resistant Paints

Brief summary & key benefits

Heat-Resistant Paints use specialised binders and pigments to withstand 300–800 °C (product-dependent) without discolouration, oxidation or flaking. Typical targets include exhaust manifolds, silencers, engine bay brackets and industrial hot surfaces. Benefits: improved corrosion protection, uniform appearance and durable matt/satin finishes. Note: poor prep causes adhesion failure and blistering.

Technical Basics

These coatings rely on silicone-modified resins, acrylic/alkyd backbones and, in some formulas, ceramic or aluminium flakes for thermal stability. Typical dry film thickness is 15–30 µm per coat; performance comes from multiple thin layers rather than one heavy pass. Substrates include carbon steel, stainless, aluminium and heat-resistant alloys; aim for clean, slightly roughened metal.

Preparation: remove rust mechanically (wire brush, P240–P400 sanding), then degrease with IPA or silicone remover. Many systems are designed for direct-to-metal use; primers should only be used where the manufacturer explicitly allows a high-temp primer.

Application: work at 18–25 °C in a dust-free, ventilated area. Shake for 2–3 minutes and spray from 20–30 cm with a cross-coat pattern. Allow 5–10 minutes flash-off between coats. Expect dust-free in 10–20 min, touch-dry in 30–60 min and full cure in 24–48 h at 20 °C; final hardness arrives after heat curing.

Curing/heat cycling: ramp temperature progressively (e.g., 100 → 250 → 650 °C) to avoid film lift. Exhaust parts naturally go through such cycles during first runs; avoid shock heating which may cause wrinkling.

Performance checks: cross-hatch adhesion, colour retention at temperature, chip resistance and chemical resistance to oil, salt and detergents. Aluminium-pigmented films hide minor substrate defects; deep matt black offers an OEM-like look on exhausts.

Selection Criteria

1) Temperature rating — choose according to the hottest location (manifold > muffler). Exceeding the rating leads to discolouration and chalking.

2) Substrate & condition — raw steel vs casting vs aluminium behave differently; unify texture by light sanding and remove weld slag.

3) Appearance — matt, satin or aluminium-flake metallic. Expect some gloss drop with repeated heat cycles; stable matt is often preferred for exhausts.

4) Chemical exposure — in the engine bay, chemical resistance may trump absolute temperature limits.

5) Application method — aerosols are perfect for spot jobs; for large panels, consider gun-applied variants if available.

Installation & Maintenance

Masking: use quality tapes for crisp lines; peel before full cure at a 45° angle. Work in adequate ventilation and keep dust away.

Layering: apply 2–4 light coats with brief flash times. If runs occur, allow to dry fully, then correct with P800–P1000 wet sanding before re-spraying. Avoid heavy single coats which crack during heat cycling.

Initial curing: after assembly, run the engine at idle for 10–15 minutes, cool down, then perform a medium-load cycle. Avoid rapid overheating. Do not use harsh cleaners for the first 72 hours.

Care: clean with pH-neutral products only; never spray cold water on hot coated parts—thermal shock may cause micro-cracks and colour shift.

FAQ

Q: Do I need a primer under heat-resistant paint?
A: Many systems are direct-to-metal. Use a compatible high-temp primer only when the manufacturer specifies it for better adhesion.

Q: How long will the coating last on an exhaust?
A: With proper prep and curing, years of service; lifespan depends on heat cycles and stone-chip exposure.

Q: What causes blistering or lifting?
A: Contamination, heavy coats or rapid heating. Clean thoroughly, spray thin layers and cure gradually.

Q: Can I topcoat with clear?
A: Only with a heat-resistant clear that is part of the system; standard clears may discolour or soften.

Q: When is washing safe?
A: After full cure (typically 48–72 h) and only with pH-neutral detergents.