Abstract
Accelerated laboratory testing is a critical part of selecting coating systems for atmospheric corrosion protection. It provides a method of classifying the performance characteristics of a coating system in a short time without presenting risk to existing facilities. However, the method must be predictive and useful. During the last decade new directions have been developed in testing of protective coatings. New methods are based on the idea that a combination of stresses in cyclic testing instead of one continual stress (e.g. ASTM B117 Salt Fog test) may better simulate real field conditions. As a result, several standards have been developed in USA and Europe such as ASTM G85, D5894, NACE TG 260 (proposed), and ISO 20340 (proposed). Each standard implements cyclic exposures. They share a common basic testing philosophy, but still have differences in some testing variables. More work is needed to quantify each test variable and its effect in order to move toward a faster more accurate standard test method. This paper provides some comparison between the various cyclic weathering test methods used to predict atmospheric coating performance. Coating film stress data was collected to quantify the individual effect of cyclic test components. Additional work was conducted in an attempt to correlate shorter term EIS (Electrochemical Impedance Spectroscopy) data and cathodic disbondment testing to conventional cyclic weathering results.
