Industrial and Specialised Coatings
Industrial and Specialised Coatings
This domain tests high-performance systems: intumescent, epoxy, polyurethane, zinc-rich, powder, coil and chemical-resistant coatings. Questions focus on service conditions, film build and recoat windows.
Systems and uses
- Intumescent coatings swell under heat to insulate steel and protect its fire rating. They are applied to a specified dry film thickness and often need a sealer or topcoat.
- Zinc-rich primers protect steel sacrificially; they are used as part of a multi-coat system.
- Epoxy gives chemical and abrasion resistance for floors, tanks and pipework. It chalks in UV, so exterior use needs a polyurethane topcoat.
- Polyurethane and polysiloxane topcoats give colour and gloss retention.
- Glass-flake and high-build epoxies resist immersion and abrasion.
- Powder coating is applied electrostatically and cured in an oven; it gives a tough factory finish.
- Coil coating is a continuous factory process for sheet metal.
- High-temperature coatings must resist heat without blistering and are applied in thin coats.
Worked example
A steel beam needs 60 minutes fire resistance. The intumescent data sheet gives 350 µm total DFT for the section factor. The applicator applies two coats of 175 µm within the recoat window and checks DFT with a gauge. The reasoning is that fire performance depends on achieving the specified DFT, not merely on the number of coats.
Traps
- Exceeding the recoat window and getting intercoat adhesion failure.
- Applying epoxy as a exterior topcoat without UV protection.
- Measuring intumescent DFT on a soft film or without the correct gauge.
- Assuming powder coating can be applied on site like liquid paint.