ABSTRACT
Construction metals are expected to have excellent mechanical properties and machinability at a low price, while at the same time they should be corrosion resistant. These properties can seldom be met in one and the same material. Separating the base metal with good mechanical properties from the corrosive surrounding by applying a surface layer can solve this problem. These layers can be:
1. Metallic layers 2. Nonmetallic inorganic layers such as conversion layers, anodized layers, some
ceramic chemical vapor deposition (CVD) and physical vapor deposition (PVD) layers, and enamel layers
3. Organic layers such as paints, lacquers, and polymer sheets
In this chapter we will discuss organic layers. The use of organic coatings for the protection of metals against corrosion is widespread in building, construction, food packaging, automotive, and marine applications. For these applications, typical and mostly successful types are developed. The choice of coating also depends on the type of substrate-steel, galvanized steel or aluminum-combined with speciŽc surface treatments. Evaluation of coating quality on site on a ship, a building, a car, or structural steelworks normally takes place when visible deterioration or defects occur. Moreover, apart from cleaning schedules, coating maintenance is usually a matter of planned repainting or unexpected repair when the coating fails. The development of coatings is mainly based on years of experience and accelerated testing in salt fog and humidity chambers, Q-UV, Weather-O-meters, Kesternich, etc. The conditions in these tests are based on the physical or chemical load in practice that is assumed to be the most important, and moreover the load is increased in order to speed up coating aging or corrosion. In these tests that are also used for screening of existing
20.6.4 Flash and Early Rust ..............................................................................................885 20.6.4.1 Early Rusting ...........................................................................................885 20.6.4.2 Flash Rusting ...........................................................................................885
