A German research team says it has developed a rapid test to better evaluate the protective abilities of water-based coating systems.
“Due to European REACH regulation, water-based corrosion protective coatings are a focus of interest,” said Dr. Matthias Wanner, who heads the project for the Fraunhofer Institute for Manufacturing Engineering and Automation IPA in Stuttgart.
REACH (Registration, Evaluation, Authorization and Restriction of Chemical substances) is a 2007 European Community regulation on the safe use of chemicals. The measure calls for the progressive substitution of the most dangerous chemicals when suitable alternatives have been identified.
“The literature, however, often reports unfavorable short-time test results for such systems, even if they show sound performance in outdoor weathering,” Wanner told PaintSquare News.
The gap between test results and actual performance is due to the coatings’ slow film formation and the retention of hydrophilic components in the polymer film, Wanner explained.
Wanner’s team thus set out to develop a procedure “to facilitate the elution of soluble hydrophilic components (e.g. monomers, oligomers, emulsifiers etc.) from the matrix and to accelerate the film formation.”
The resulting process was accomplished by “a special wet/dry cycling of coated samples, monitored by an in situ electrochemical impedance spectroscopy (EIS),” said Wanner. After this “pre-conditioning,” the waterborne coatings “can be tested on their real long-term barrier and corrosion protective properties.”
Scientists can thus compare coatings systems without having to wait for the formation of the complete barrier effect.
In fact, pre-conditioning revealed “improved protective properties” among some water-based coatings, Wanner said. “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 water-based coatings.”
For more information, visit www.ipa.fraunhofer.de.