Exhaust pipe coating? This niche-sounding technology actually serves as the unsung hero for automotive and industrial equipment. Imagine the abuse an exhaust system endures – scorching heat, chemical corrosion, violent vibrations, even ambushes from rain and road salt. Without proper protection, metal substrates rapidly degrade, performance plummets, and maintenance costs skyrocket. So how do we keep exhaust systems resilient in extreme conditions?
Silicone resins might hold the answer. Naturally heat-resistant, chemically stable, and boasting exceptional metal adhesion. But here’s the question: With countless coating options available, why does silicone resin stand out?
Technical Challenges in Exhaust Pipe Coatings
Heat is the primary assassin. Conventional coatings begin decomposing at 300°C, while performance exhausts regularly endure 600°C+ exhaust gases. Once coatings fail, bare metal faces direct exposure to extreme heat, inevitably leading to oxidation and deformation.
Corrosion proves equally deadly. Sulfur and nitrogen oxides combine with moisture to form acidic solutions, while winter road salts introduce chloride attacks. Even premium stainless steel eventually succumbs to this relentless assault. Add constant mechanical vibrations from rough roads, and brittle coatings quickly crack and peel – negating all protective benefits.
Environmental regulations further complicate matters. Traditional solvent-based coatings face increasing restrictions due to VOC emissions, creating urgent demand for greener solutions. Can silicone resins meet all these challenges?
Why Silicone Resin for Exhaust Coating?
Thermal resistance is its signature strength. While common organic resins soften above 200°C, silicone’s Si-O bonds easily withstand 600°C+ extremes. This stability stems from Si-O bonds’ superior energy compared to C-C bonds – essentially giving exhaust systems a “fireproof suit.”
Chemical inertness proves equally crucial. Acidic exhaust, salt spray, humid air? Mere trifles for silicone resin. Its molecular structure barely reacts with common corrosive agents, functioning like an invisible shield.
Adhesion matters tremendously too. The worst coating failure is delamination, but silicone resins maintain both strong metal bonding and thermal flexibility – preventing cracks from thermal cycling.
The environmental advantage seals the deal. Waterborne silicone resins deliver high performance without high-VOC solvents, satisfying regulations without compromise. So what practical solutions exist?
Product Solutions
Solution 1: Waterborne Single-Layer Exhaust Pipe Coating (SIO-714)
As environmental regulations tighten, our waterborne silicone resin SIOResin® SIO-714 offers a high-performance, low-VOC alternative. Designed for 400-800°C exhaust environments, this single-layer solution combines application simplicity with corrosion resistance.
Applications: Mid-to-high-end OEM automotive exhaust pipes, aftermarket repairs, industrial exhaust systems
Starter Formulation
For waterborne high-temperature silicone resin coatings, the following recommended formulation can be used as a starting formula for single-component baking-type colored coatings.
Black Pigment Paste Formulation
| Component | Parts by Weight | Function | Supplier |
| Deionized Water | 531.6 | Solvent | – |
| Dispersant H-1772W | 24 | Dispersing agent | SIOResin® |
| Anti-settling Agent BYK-420 (10%) | 18 | Anti-settling agent | BYK |
| Anti-settling Agent Bentone LT (2%) | 24 | Anti-settling agent | Haimings |
| Defoamer Foamex 810 | 2.4 | Defoaming agent | Tego |
| Low-melting Glass Powder (400°C) | 200 | Enhances high-temperature adhesion | – |
| White Mica | 100 | Enhances low-temperature adhesion | – |
| Copper Chrome Black | 200 | Heat-resistant pigment | – |
| High-purity Zinc Phosphate | 100 | Improves water resistance & salt spray resistance | – |
Total: 1200 parts (Pigment & filler content = 50%)
Processing Steps:
- Add defoamer, anti-settling agents, and dispersant to deionized water. Stir at 1000 rpm for 5 minutes.
- Add copper chrome black, mica powder, low-melting glass powder, and zinc phosphate, stirring at 2000–3000 rpm for 45 minutes.
- For better fineness, use 1:1 zirconium beads for ball milling.
Black High-Temperature Coating Formulation
| Component | Parts by Weight |
| Silicone Resin Emulsion SIO-715 | 100 |
| Dimethylethanolamine or AMP-95 | 0.1 |
| Black Pigment Paste | 67 |
| Anti-settling Agent (Bentone LT, 2%) | 4 |
| Anti-flash Rust Agent | 1 |
| Defoamer (Foamex 810) | 0.1 |
| Thickener | 1–2 |
Processing Steps:
- Disperse all ingredients thoroughly until uniform, stirring at 1000–1500 rpm for 20–30 minutes.
- Adjust viscosity as needed.
- Filter through a 200-mesh filter bag before packaging.
Notes:
✔ Adjust solid content by adding deionized water as needed.
✔ For single-coat applications, control dry film thickness to 35–50 μm. Excess thickness may cause cracking. Allow previous layers to surface-dry before recoating.
✔ Initial heating must be gradual to allow the coating to undergo secondary sintering in a high-temperature environment. Avoid placing uncured coated parts directly into high-temperature conditions to prevent film cracking.
Application Process
- Stir well before application: The coating may settle after prolonged storage, so it must be fully stirred before use. Adjust spray viscosity by adding 5–10% deionized water as needed. Conduct a small-scale test before large-scale application.
- Surface Preparation: Remove oil and rust from the substrate. For large-scale applications, sandblasting, brushing, or grinding is recommended to increase surface roughness and adhesion.
- Application Method: Use high-pressure spraying. After surface drying at room temperature, proceed with baking or low-temperature drying below 80°C to accelerate surface drying. Avoid directly baking wet films at high temperatures to prevent bubbling.
- Baking Process:
- Deep curing recommended at 200–280°C for 10–60 minutes.
- Higher temperatures shorten curing time.
- Optimal curing conditions: 220°C for 30 minutes or 280°C for 10 minutes.
Precautions
✔ This coating contains multiple high-temperature resistant materials with different densities, leading to potential settling over time. Always stir well before use.
✔ After use, seal the container tightly to prevent skinning and thickening of the paint.
✔ Clean spray guns and brushes immediately with water after application to avoid residual coating drying at room temperature, which may affect future use.
Solution 2: Solvent-Based Dual-Layer Exhaust Pipe Coating (SIO-2130H + SIO-2167)
For extreme conditions like performance exhausts or turbocharger sections, our dual-layer system delivers superior protection. The epoxy-modified silicone primer (SIOResin® SIO-2130H) ensures metal adhesion and rust prevention, while the pure silicone topcoat (SIOResin® SIO-2167) provides 700°C+ resistance and abrasion protection.
Applications: Racing exhausts, heavy-duty diesel systems, high-temp industrial piping
Formulation for 700°C Heat-Resistant Black Silicone Exhaust Paint(Top coat)
SIO-2167: 48–52
Chromium Copper Black: 5–7
Talc Powder: 15
Mica Powder: 10–15
Low-Melting Glass Powder: 7–10
Bentonite: 0.3–0.5
Dispersant: 0.5 Silane Coupling Agent KH-560: 1–2
Diluent (Toluene, Xylene, Butyl Ester): Appropriate amount
Notes:
1 High-temperature-resistant black pigments can also include enamel black, ceramic black, or
graphite. The amount added can be increased or decreased depending on the desired
blackness, with the filler quantity adjusted accordingly.
2 For applications requiring heat resistance below 600°C, low-melting glass powder may be
omitted.
Solution 3: Solvent-Based Single-Layer Exhaust Coatings (SIO-2130H)
When balancing budget and performance, our epoxy-modified silicone resin SIOResin® SIO-2130H offers cost-effective 300-600°C protection with better heat resistance than standard epoxies.
Applications: Economy vehicle exhausts, motorcycle exhaust pipe coating, agricultural machinery, general industrial systems
Heat-Resistant Black Silicone Paint (Baking Type) for 500~600°C
- SIO-2130H: 48~52
- Chromium Copper Black: 5~7
- Talc Powder: 10~15
- Mica Powder: 7~10
- 450°C Low-Melting Glass Powder: 5~7
- Bentonite: 0.3~0.5
- Dispersant: 0.5
- Amino Resin 5847 (5747): 5~8
- KH560: 1~2
- Thinner (Toluene, Xylene, Butyl Acetate, etc.): As needed
Note:
The black heat-resistant pigment can also be manganese iron black, enamel black, ceramic black, etc. The amount can be increased or decreased based on the required blackness, with corresponding adjustments to the filler content. The low-melting glass powder is optional.
Selection Guide
Facing three solutions, you might ask: Which fits my needs? Focus on three factors: temperature, environmental compliance, and budget.
• Need >600°C resistance and superior corrosion protection? Choose dual-layer (SIO-2130H + SIO-2167)
• Prioritizing low VOC? Waterborne single-layer (SIO-714) excels
• Budget-conscious but need heat resistance? Solvent-based single-layer (SIO-2130H) offers best value
Real-world applications often demand more nuance – like industrial exhausts requiring both extreme heat and chemical resistance. For these cases, customized formulations may be ideal. Our technical team can optimize coating systems for peak performance.
About SIOResin (SIO New Material)
SIOResin is a leading company in China specializing in the development and production of new materials. We manufacture and supply high-quality water-based silicone resins, silicone-modified polyesters, water-based polyurethanes, water-based acrylics, UV resins, liquid silicone rubber, intumescent fireproof coatings, flame retardants, wetting agents, curing agents, associative thickeners, driers, soft-touch agents, and other additives. Our products have a wide range of applications and with competitive prices.
To learn more or to request samples, feel free to contact us. We are always here to help with your adhesive needs!