A British Standard ISO 12944 has been developed which grades environments by their corrosive effect to enable informed decisions to be made as to whether a duplex marine coating or a lesser coating, is needed to properly protect an item.
Part 2 covers the classification of environments. The gradings start at C1 which covers buildings and equipment in dry, cold areas with low pollution and low corrosivity. It moves through C2, C3 & C4 to C5 where there is very high pollution and/or significant levels of chlorides. This has generally been adopted by the powder manufacturers to define which of their products are suitable for these environments along with film thickness etc.
It is important that you define, on a site by site basis, which environment classification you have.
C4 is typically found on sites near the coast and covers the categories where a duplex marine coating is needed. This includes areas where items that need protection might be subject to an industrial, high humidity, or aggressive atmosphere. It also covers coastal areas that have high salinity. We would suggest that if product is to be installed within 2km of the coast then the cost benefit analysis of a marine coating should certainly be considered.
When specifying coatings for these environments it is important that you ask your supplier to provide data from the powder manufacturer showing which of their powder products will suit the application, this should also include the required film thickness.
With the environment suitably classified and a suitable powder presented by your supplier we recommend that you specify powder coating in accordance with BS EN 13438. This standard is in depth and covers film thickness, pre-treatment requirements and meaningful quality control/destructive testing.