New prescreening test for waterbased corrosion protection systems
Due to European REACH regulation waterbased corrosion protection coatings are in the focus of interest. The literature, however, often reports unfavourable short-time test results for such systems, even if they show sound performance in outdoor weathering. This discrepancy relates to the extended duration of the film formation and the retention of hydrophilic components in the polymer film. In order to overcome this discrepancy, a procedure has been developed to facilitate the elution of soluble hydrophilic components (e.g. monomers, oligomers, emulsifiers etc.) from the matrix and to accelerate the film formation. This is accomplished by a special wet/dry cycling of coated samples, monitored by an in situ electrochemical impedance spectroscopy (EIS). First after this pre-conditioning the waterbased coatings can be tested on their real long-term barrier and corrosion protective properties. For some such pre-conditioned waterbased coatings improved protective properties have been found. Moreover, it became apparent that the early EIS monitoring during the pre-conditioning provides valuable data about the properties of the tested coatings. These data can be used for a pre-screening and optimal formulation of waterbased coatings.