Powder Coating

A tough and versatile finish

Powder coating is a hard, durable decorative finish that can be applied to steel and aluminium. It is available in a wide range of colours and textures, including metallic and hammer finishes.

The process

Metals are coated in electro-statically charged plastic particles, baked on at 200 degrees, to produce tough but decorative finishes in a vast range of colours and surface textures.

Powder coats, such as epoxies and polyesters, provide hard impact-resistant coating 40-80 microns thick. These are commonly in use for decorative applications and can be matt, gloss, textured and hammered in appearance.

Coating thicknesses can be controlled by pre-heating the work or by varying the amount of powder applied.

Pre-treatment selection

As with all finishing, the selection of the pre-treatment is important to achieve the right results.

Internal mild steel will generally be shot-blasted prior to coating, to clean off mill scale and give an adequate key for the surface.

Steel for external purposes will normally be coated with zinc, which will be degreased and 'converted' prior to powder coating. This is done using phosphate treatment, which etches the surface and allows the powder to key securely to the substrate.

Aluminium is degreased and the surface etched with chromate give a chemical and mechanical key.

Options for zinc coating steel to rust-protect it are discussed below.

Rust protection - the choices for steel

Where steel is being exposed to the elements, various options are available:

Hot zinc spraying

  • This finish is as rust-resistant as galvanising, but has a more consistent and smooth surface to key to than and galvanised.

Powder coating

  • Powder coating onto hot zinc gives a very high quality finish - durable, flat and extremely
    will bonded together. Blastreat’s top quality zinc spraying and powder coating finish is
    second to none.

Zinc rich primer

  • This is a power primer that is applied prior to powder coating with the final colour. This will give most of the characteristics of zinc spray in terms of quality of surface finish, but it is generally accepted that flame applied zinc or galvanising is superior in rust protection.


  • Hot dip galvanising is tough and durable but somewhat 'industrial' in that the surface finish is
    unpredictable. It does have the advantage of coating the insides of tube sections but may also damage and distort delicate work and needs considerable 'fettling' to make it suitable for coating (Blastreat can arrange quality control if required).


  • BS 6496 : 1984 Powdercoating of aluminium
  • BS EN 13 438 : 2005 Powdercoating of galvanised steel


  • We have two large ovens, the largest of which is 6.4m long x 3m wide
    x 3m high, which enables us to handle both large and heavy items.

Testing and inspection

  • We use film thickness gauges, apply cross hatch adhesion tests, scratch resistance tests and gloss level tests.In addition to our own high internal quality standards we run a comprehensive
    QA and inspection procedure to check work to conformity to British Standards.
  • All finished work is checked and wrapped for protection during transport.
  • We can supply matching aerosol touch up paint if required for large items, in case the work is damaged during use.