Assessment of water permeability of organic coatings by eis and alternative techniques

摘要

The principal function of an organic coating is to form a barrier between corrosive environment and metal.Although paint systems used in coil-coating industry are not able to provide full barrier effect,they do limit the access of ions,oxygen and water to the metal surface.The goal of this work was to compare techniques used for water uptake and water diffusion measurements in organic coatings in order to identify those applicable for coil-coated materials,to assess their limits and reproducibility and to verify if complementary information can be obtained by using several of them.Namely,gravimetry in humid air,gravimetry in liquid water,thermogravimetry,electrochemical impedance spectroscopy(EIS)and a cup method using blind hole samples have been compared.Attention was paid also to evaluation and interpretation of obtained data.