ABSTRACT
This chapter presents a brief overview of the major mechanisms that cause aging and subsequent failure of organic coatings. The major weathering stresses that cause degradation of organic coatings are UV radiation, moisture, heat, and chemical damage. In general, reflectance and transmittance pose no threats to the life span of the coating. Absorption is the problem. When energy from the sun is absorbed, it leads to chemical destruction. The uptake of water affects the coating in several ways: (1) chemical breakdown; (2) weathering interactions; (3) hygroscopic stress; and (4) blistering and adhesion loss. The two types of blistering in anticorrosion paints— alkaline and neutral— are caused by different mechanisms. At slightly elevated temperatures, crosslinking of the polymer will continue, making the film stiffer and harder. In a study, performed in Spain, indicates that humidity played a more important role than levels of atmospheric contaminants in predicting corrosion of painted steel.
