Fundamental properties, long-term service characteristics, and specification writing and testing for various kinds of hot applied coal tar enamels are described. Emphasis is directed to the importance of long-term testing of coating types previously found to perform satisfactorily in service in various environments over long periods of time. A brief history of the use of hot applied coal tar coatings also is given.
Technique of application and a list of commonly used types of pipe coating are given. Data are tabulated for eight plasticized and seven unplasticized enamels with respect to softening point, penetration, percent ash, specific gravity, high temperature sag and low temperature crack. Water absorption rates are plotted for several pipe line enamels. On other graphs the relationship between rate of shear and shearing stress is shown for a number of roofing pitches. Electrical resistivity, soil stress resistance, and oil spillage resistivity are discussed in connection with coal tar enamels. 5.4.5
