Protective coatings, such as paint and powder coatings, applied to steel provide barrier protection. As barrier protection is dependent on the integrity of the coating, the selection, application, and handling of painted and powder coated materials is very important. It is imperative these coatings are handled with care during installation and if damaged are repaired to ensure they are as durable as planned.
All organic forms of barrier protection are permeable to some degree, and once the protective coating is penetrated, the corrosion resistance is compromised. Most paints and powders are porous and easily damaged, allowing electrolytes (moisture, humidity) to reach the underlying steel. If regular maintenance is not performed, underfilm corrosion begins and the coating can fail in a relatively short period of time. There is no cathodic protection provided by paints and powder coatings, which limits their time to first maintenance to ten years or less in most environments.
Both paint and powder coatings can be used in conjunction with hot-dip galvanizing, known as a duplex system. The two coatings work in synergy to provide surperior corrosion protection, while allowing a specifier to suit any aesthetic preference.