INDUSTRIAL MAINTENANCE COATINGS COVER A diverse range of coatings for use in a wide variety of industries. For example, coatings such as alkyds, acrylics, vinyls, epoxies, urethanes, polyureas, silicones, and silicates can be used to coat structures of such variety as bridges, railroad cars, chemical process vessels, elevated water tanks, and concrete floors. Therefore, it is obvious that because of the many different coating chemistries and the vast range of environments to which they might be exposed, the testing of industrial maintenance coatings can be a broad topic. Furthermore, a particular physical property which may be important in one application, such as temperature resistance for a stack coating, may be of little importance for a different coating in a different environment. Therefore, it is important to know not only what type of tests can be run, but to appreciate the relative importance of various tests, realizing that their ranking may change from project to project. In broad terms, the testing of coatings falls into one of two categories: determining the properties of the liquid paint, and determining the properties of the dried film. The testing of liquid paint can involve not only determining compositional related parameters such as density or solids content, but also application related parameters such as dry time and sag resistance. Although dried films can certainly be subjected to a barrage of analytical techniques to investigate chemical composition, this would generally be considered a separate topic, and in the context of this chapter most of the testing on dried films is done to determine performance or physical properties, such as abrasion resistance or adhesion. In the past, much emphasis, not only in testing but in specification writing, was placed on the chemical composition of the coating. In the last decade or so, the emphasis has shifted more toward performance based requirements. Although the performance of the coating on the substrate is certainly of more fundamental importance than which ingredients are in the can, the latter should not be ignored. Indeed, it is fairly common when screening coatings for a Qualified Products List (QPL) to base acceptance on their performance characteristics, but also to do some basic compositional testing of the specific batch which was submitted. The results of these compositional tests are then used to define the characteristics of any future batches which may be provided for specific jobs, to help insure that production batches have similar composition (and therefore hopefully similar performance characteristics) to the batch which passed the QPL testing.