Adding extra corrosion resistance to your product, and also the perfect surface to achieve the highest level of appearance. When used with a mechanical profiling process, liquid chemicals can largely be avoided.
Corrosion is the natural process in which a metal is eaten away and changed by chemical and/or electrochemical action from exposure to the environment. When the substrate is steel, corrosion is usually referred to as rusting and it is formation of iron oxides in the presence of oxygen, water and salt and other chemicals such as acids that may accelerate the process.
Rusting leads to huge costs for the end user if the steel is not suitable protected. Poor protection leads to more frequent maintenance, repair and replacement.
Corrosion occurs at different rates, depending on the working environment the steel is in. Before specifying the coating system, considering the likely environment is vital. International standard ISO 12944-2 categorises environments into 5 classes.
| Environmental Category | Corrosivity | Indoor | Outdoor |
| C1 | Very low | Heated buildings such as offices, schools and shops. | |
| C2 | Low | Non-heated buildings such as warehouses or sports halls | Arid inland with low pollution level, particularly rural areas. |
| C3 | Medium | Production rooms with high humidity and some air pollution, eg food processing plants, laundries, dairies. | Low salinity coastal areas. Urban and industrial atmospheres with low pollution |
| C4 | High | Chemical manufacturing, swimming pools, shipyards. | Industrial areas and coastal areas with moderate salinity |
| C5 | Very high | Buildings with high pollution and near-permanent condensation, eg steam rooms, chemical factory, closed swimming pools. | The very harshest of shore environments with high salinity. Industrial areas with aggressive atmospheres. |
Corrosion begins at weak points in the coating system. These are areas either with poor design elements, areas poorly prepared before powder coating, or areas with too low film thickness. Examples of poor design elements are:
No matter how well the fabricated parts are designed, sharp edges are almost always present from laser cutting, stamping or guillotining. Sharp edges are weak points and can lead to corrosion within weeks after powder coating application. This is caused by the desire for high flow coatings, which pull away from the edge during the curing process, leaving the corner with little or no film build.
All multicoat systems will provide a high protection at the sharp edges, and the edge covering HMG primers will hold fast to the sharp corners during stoving, protecting sharp edges and preventing premature corrosion.
Steel should be thoroughly cleaned and either
The choice of treatment process prior to powder coating will depend on the local environmental factors and lifetime expectations of the powder coated product.
| Location | Expected Lifetime* | Salt Spray | Preparation | Primer | |
|---|---|---|---|---|---|
| C3 | High >15 years | 480 hours | Chemical | Iron or zinc phosphate | NZP |
| Mechanical | Grit blast | NZP | |||
| C4 | Medium 5 - 15 years | 480 hours | Mechanical | Grit blast | NZP |
| High >15 years | 720 hours | Chemical | Iron or zinc phosphate | NZP | |
| Mechanical | Grit blast | Epozinc 1000 | |||
| C5 | High >15 years | 1,440 hours | Chemical | Zinc phosphate | NZP |
| Mechanical | Grit blast | Epozinc 1000 |
*’Expected Lifetime’ is an indication of foreseen useful life, taken from the ISO 12944 standard. It is not a warranty or guarantee period. Regular maintenance of coated materials will maximise durability.
Zinc-free epoxy polyester primer. Available in a variety of colours.
TECHNICAL DATA SHEET (PDF )Galvanised substrates contain gases trapped during the creation of the iron-zinc alloy and zinc layer. These gases escape during the powder application process, causing cratering and weak spots in the protective coating layer.
Eposeal barrier primer is specially formulated to allow outgassing of the substrate without the cratering of the surface and to protect the surface from corrosion. It also provides an excellent smooth surface for the final polyester top coat to provide a surface of excellent smoothness. Where a 'ripple' texture final coat is specified, we recommend the use of a primer to provide an adequate minimum film thickness.
Before application, the zinc surface should be thoroughly cleaned and profiled, which may be acheived either chemically or mechanically by a gentle sweep blast using a non-ferrous media.
| Location | Expected Lifetime* | Salt Spray | Preparation | Primer | |
|---|---|---|---|---|---|
| C4 | High >15 years | 720 hours | Mechanical | Sweep blast | Eposeal |
| C5 | High >15 years | 1,440 hours | Chemical | Zinc phopshate | Eposeal |
*’Expected Lifetime’ is an indication of foreseen useful life, taken from the ISO 12944 standard. It is not a warranty or guarantee period. Regular maintenance of coated materials will maximise durability.
Epoxy barrier primer specially designed for zinc surfaces. Available in a variety of colours.
TECHNICAL DATA SHEET (PDF )Designed to have an excellent build, and be sandable without clogging. This light grey product provides an excellent smooth surface on which to create the perfect effects over aluminium and magnesium alloy wheels.
These primers are designed to be sprayed onto a surface, usually to protect the product before a final finish, usually a liquid paint, is applied. The time between applying the primer and top coat may stretch to weeks. The primers are designed to be fully cured before final finish application.
We can make any powder coating colour or finish to order so get in touch to discuss your requirements.