This paper starts by putting forward a mechanism for the way that anti-corrosive paints work. This draws on previous work on understanding of mechanism but puts stronger emphasis on the maintenance of the oxide film of the metal under the paint as the essential feature. If this mechanism is correct then it suggests various properties which a paint coating should have. In many cases a minimum value of these properties is all that is required. In some cases e.g. DC resistance, it is advantageous to have as high as possible value of this property at the start due to degradation with time. The paper then details a series of tests, chosen by the authors for their relative simplicity, to measure these properties in a quantitative manner and hence to assist in formulation of new or better coatings. These tests are the personal selection of the authors and we admit that others may make different choices. They have been divided into those best conducted on the free paint film and those which are conducted on the metal and paint together, the latter including one test to be conducted on the metal alone. Among the second group, suggestions have been made for electrochemical tests which are non-destructive and can thus be used for quality control and monitoring. There is a brief discussion of accelerated tests with the emphasis again on quantitative non-destructive assessment methods. Numerous pertinent references are provided. The papers concludes with suggestions for future work.