A high-temperature coating develops a crack, chip, or peel. The instinct is often to strip and recoat the entire component. In many cases, localized repair is practical, less expensive, and achieves the same outcome. Understanding when and how to repair prevents unnecessary downtime and cost.
When Repair Is Practical
Small areas: Cracks or chips under 1 square inch are repairable
Isolated damage: Damage in one location; rest of coating is sound
Non-critical areas: Damage in areas not subject to high stress or extreme conditions
Budget constraints: Repair costs 10–20% of full recoating
Time constraints: Repair requires hours; full recoating requires days or weeks of cure time
When Full Recoating Is Necessary
Large damage: Coating damaged over more than 5–10% of the surface
Multiple locations: Damage in many areas suggests systemic failure; recoat is more economical
Widespread peeling: If coating is peeling in multiple spots, expect more peeling soon; recoat
Structural exposure: If bare substrate is exposed and the component is under load, repair is a temporary fix
Corrosion visible: If corrosion has begun on the exposed substrate, it will continue; full recoat + corrosion treatment is necessary
Repair Process
Step 1: Access the Damage
For coatings under insulation:
– Carefully remove or cut away insulation to expose the damaged area
– Plan to re-insulate after repair
– Ensure no water intrusion during repair
For exposed coatings:
– Clean and prep the damaged area
Step 2: Remove Damaged Coating
For small cracks or chips:
– Use a small grinding wheel or cutting tool to widen the crack slightly
– Remove all loose coating and rust
– Sand the area with 80–120 grit to clean bare metal
– Feather the edges outward (sand a wider area beyond the damage) to blend with existing coating
For peeling areas:
– Remove the peeling coating completely
– Sand the exposed surface and edges
– Remove all dust
Step 3: Prepare the Substrate
- Clean: Wipe with solvent to remove oil and dust
- Dry: Allow to air-dry (20–30 minutes)
- Inspect: Check for rust or corrosion on the exposed substrate
- Treat if necessary: Apply rust converter if rust is present
Step 4: Prime (Optional but Recommended)
For exposed bare metal:
– Apply primer matching your topcoat system
– Single thin coat is typically sufficient
– Allow to cure per primer specifications (often 24 hours)
Step 5: Apply Topcoat
Match the existing coating:
– Use the same coating system as the original (ceramic, paint, silicone)
– Color matching is challenging—touch-ups will likely be slightly visible
Application:
– Thin coats (1–2 mils per coat)
– Apply 2–3 coats to match existing thickness
– Feather the edges outward to blend with existing coating
Blending:
– Sand lightly (220–320 grit) between coats to improve adhesion
– Final coat can be feathered outward to create a seamless blend with existing coating
Step 6: Cure
- Allow full cure time before returning to service
- Ceramic: 7 days typically
- Paint/silicone: 3–5 days typically
- Do not expose to service temperature or stress until fully cured
Step 7: Re-Insulate (If Applicable)
- Re-install insulation over repaired area
- Ensure insulation is tight; gaps allow moisture entry
- Seal any gaps with tape or sealant
Special Challenges
Repairing Under Insulation
Challenge: Access is difficult; risk of water entry during repair
Solution:
– Work quickly to minimize exposure time
– Have replacement insulation ready
– Consider temporary protective covering during repair
– Apply hydrophobic sealant around repair area before re-insulating
Color Matching
Challenge: Existing coating has faded or discolored; new application will look obviously patched
Solution:
– Accept that the patch will be visible
– Feather edges carefully to minimize visual impact
– Plan for eventual full recoating when cosmetic improvement is desired
– Use tinted primer to approximate existing color if available
Feathering Large Edges
Challenge: Feathering from new coating to old coating over a wide area is difficult
Solution:
– For small damage (<1 inch): Feather over 2–3 inch radius
– For larger damage: Accept some visible edge; feather what is practical
– Sand existing coating lightly (220–320 grit) at the boundary to improve new coat adhesion
Thick Existing Coatings
Challenge: If existing coating is very thick (10+ mils), matching thickness in a repair is difficult
Solution:
– Add enough coats to approximate thickness (or accept slightly thinner repair)
– Feathering helps blend thickness differences
– A 10% thickness difference is usually acceptable
Documentation
Record the repair:
– Date of repair
– Location of damage
– Type of coating used for repair
– Expected re-inspection date
This helps track if the same area keeps failing (suggesting a systemic problem).
Cost Analysis
Localized repair of 1 sq in area:
– Prime: $5–10
– Topcoat: $10–20
– Labor: 1–2 hours
– Total: $50–100
Full recoat of large component:
– Surface prep: $200–500
– Prime: $50–100
– Topcoat: $100–300
– Labor: 8–16 hours
– Total: $500–$1,000+
Localized repair costs 1/5 to 1/10 of full recoating.
When to Plan Full Recoating
If repairs are needed more frequently than every 2–3 years, consider full recoating. Frequent failures suggest the coating is aging or the surface prep was inadequate in the original application.
Email Us if you need guidance repairing a damaged high-temperature coating, or if you’re experiencing frequent coating failures in the same area.
The Bottom Line
Localized repairs are practical for small cracks, chips, and small peeling areas. Strip the damaged area, feather edges, apply matching coating, and cure fully. Blending color and thickness will not be perfect, but the repair is effective and durable. For extensive damage or frequent failures, plan full recoating instead. Document repairs to track if systemic coating failure is developing.
Visit www.incurelab.com for more information.