High temperature coatings occupy a narrow, unforgiving niche. Get the grade or the application wrong and the failure is fast and visible: peeling aluminium flakes on a stack, rust streaks on hot pipework within months. The causes repeat, and all four are avoidable at specification stage.
1. The wrong temperature number
Coatings are rated for continuous service temperature; excursions and cycling are different questions. A line that runs at 180 C but spikes to 320 C on regeneration needs the higher rating. Measure, do not assume; the difference between a silicone acrylic and a full silicone aluminium coating is exactly this number.
2. Too much film
Silicone coatings must be applied thin, typically 25 to 40 microns per coat. Painters used to high build epoxies routinely double that, and the film cracks and delaminates on first heat up as solvents and stresses release. Thin, even coats, full stop.
3. Conventional primer underneath
Standard primers decompose at temperature. Hot service systems are either applied direct to blasted steel or over an inorganic zinc silicate rated for the range. Any organic primer under a 500 C service coating is a built in failure.
4. Cure by heat never completed
Many silicone aluminium grades only reach full properties after a controlled first heat cycle. If the unit start up is months away, the soft film picks up damage in the interim. Plan protection and handling accordingly.
Corrosion under insulation deserves its own article, and has one coming this week. For grades, temperature ratings and same day quotations from Dubai, see our oil, gas and refinery coatings page.