title: Preservation of York Minster historic limestone by hydrophobic surface coatings.
abstract: Magnesian limestone is a key construction component of many historic buildings that is under constant attack from environmental pollutants notably by oxides of sulfur via acid rain, particulate matter sulfate and gaseous SO(2) emissions. Hydrophobic surface coatings offer a potential route to protect existing stonework in cultural heritage sites, however, many available coatings act by blocking the stone microstructure, preventing it from 'breathing' and promoting mould growth and salt efflorescence. Here we report on a conformal surface modification method using self-assembled monolayers of naturally sourced free fatty acids combined with sub-monolayer fluorinated alkyl silanes to generate hydrophobic (HP) and super hydrophobic (SHP) coatings on calcite. We demonstrate the efficacy of these HP and SHP surface coatings for increasing limestone resistance to sulfation, and thus retarding gypsum formation under SO(2)/H(2)O and model acid rain environments. SHP treatment of 19th century stone from York Minster suppresses sulfuric acid permeation.
authors.affiliation: Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK.
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Walker
authors.forename: Karen
authors.initials: K
authors.lastname: Wilson
authors.forename: Adam F
authors.initials: AF
authors.lastname: Lee
authors.forename: Julia
authors.initials: J
authors.lastname: Woodford
authors.forename: Vicki H
authors.initials: VH
authors.lastname: Grassian
authors.forename: Jonas
authors.initials: J
authors.lastname: Baltrusaitis
authors.forename: Gayan
authors.initials: G
authors.lastname: Rubasinghege
authors.forename: Giannantonio
authors.initials: G
authors.lastname: Cibin
authors.forename: Andrew
authors.initials: A
authors.lastname: Dent
mesh_terms: D015258:Acid Rain; D002119:Calcium Carbonate / Q000737:chemistry*; D002133:Calcium Sulfate / Q000737:chemistry*; D003252:Construction Materials / Q000032:analysis; D004785:Environmental Pollutants / Q000737:chemistry; D005227:Fatty Acids / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D008855:Microscopy, Electron, Scanning; D008956:Models, Chemical; D010087:Oxides / Q000737:chemistry; D010316:Particle Size; D052638:Particulate Matter / Q000737:chemistry; D012821:Silanes / Q000737:chemistry*; D013431:Sulfates / Q000737:chemistry; D013457:Sulfur Compounds / Q000737:chemistry; D013464:Sulfuric Acids / Q000737:chemistry; D013499:Surface Properties; D014961:X-Ray Diffraction
chemical_list: D015258:Acid Rain; D004785:Environmental Pollutants; D005227:Fatty Acids; D010087:Oxides; D052638:Particulate Matter; D012821:Silanes; D013431:Sulfates; D013457:Sulfur Compounds; D013464:Sulfuric Acids; C405951:sulfur monoxide; D002119:Calcium Carbonate; C033158:sulfuric acid; D002133:Calcium Sulfate