Coating steel chimneys and stacks
Steel chimneys and stacks spend their working lives exposed to wind, rain and whatever the surrounding air carries. Without an effective coating, the outer steel will corrode, so the coating system matters as much as the fabrication.
Why chimneys need a coating system
A chimney is a tall, exposed structure that is costly to access once it is installed. That makes it sensible to get the protective system right at the start, when the sections are on the ground and every surface can be reached. A well-applied system reduces the need for early maintenance at height.
Preparing the steel
Coating starts with surface preparation. Fabricated chimney sections are usually abrasive blast cleaned, which removes mill scale, rust and contamination and leaves a clean, profiled surface for the primer to grip. The specification sets the standard of cleanliness required, and the first coat should follow promptly so the prepared steel does not start to rust again.
Building up the system
A typical system is built up in layers, each with its own job:
- Primer coats provide the corrosion-protective base and give the following coats a sound surface to bond to
- A topcoat, such as a polyurethane, forms the outer layer that faces the weather and gives the finished colour
The exact products, the number of coats and the thickness of each are set by the specification for the project. Where the chimney steel will run hot in service, the coating must also be suitable for its operating temperature, which is a decision for the specifier and the coating manufacturer.
Handling, transport and installation
Coated chimney sections are heavy and are lifted, transported and bolted together after coating. Lifting points, flanges and edges can be damaged along the way, so plan for inspection and touch-up with compatible materials once the sections are in place.
A worked example
On Steel chimney coatings, Stoke, MCP Painting Group coated a set of steel chimney sections off site, at the steel company’s premises, after they had been shotblasted by a specialist preparation company we work closely with. The steel received two coats of primer followed by a single coat of durable polyurethane topcoat for protection against atmospheric exposure. The case study shows the sections at the primed stage and with the finished topcoat.
Getting your chimneys coated
If you manufacture or install steel chimneys and stacks and need the sections primed and coated, read about our steel coating services for fabricators or get in touch with our team.