New coating can protect historic buildings

Historic limestone buildings and statues can be protected from pollution with a single layer of a water-resistant coating, U.S. and British researchers say. A University of Iowa researcher and her colleagues from Cardiff University, writing in the journal Scientific Reports, say they've developed a new way to minimize chemical reactions that cause buildings made of limestone to deteriorate. "This paper demonstrates that buildings and statues made out of limestone can be protected from degradation by atmospheric corrosion, such as corrosion due to pollutant molecules and particulate matter in air, by applying a thin, one-layer coating of a hydrophobic coating," Vicki Grassian, an Iowa professor of chemistry and chemical and biochemical engineering, said. The coating includes a mixture of fatty acids derived from olive oil and fluoridated substances that increase limestone's resistance to pollution, the researchers said. One of the buildings examined in the study was York Minster, a cathedral located in York, England, and one of the largest structures of its kind in northern Europe. Construction of the cathedral began in the 1260s. York Minster was a perfect structure to study and test the coating, Grassian said, because its limestone surface has been exposed for decades to acid rain, sulfur dioxide and other pollutants. "We showed in particular that the degradation of limestone from reaction with sulfur dioxide and sulfate particles could be minimized with an application of this coating."