J.CAC VOLUME 32 (2007)
Biodeterioration and Performance of Anti-graffiti Coatings on Sandstone and Marble
The ability of three commercial anti-graffiti products, Fluorolink® P56 (a fluoropolymer), Weather Seal Blok-Guard® and Graffiti Control (a silicone elastomer), and Protectosil® Antigraffiti (a silane), to provide protection from graffiti attack was evaluated on Wallace sandstone and Mississquoi marble. Results suggested that the coatings affected the colour of the stones, rendering samples darker with increased yellow values. Water absorption of the sandstone decreased with anti-graffiti coatings. The application of protective coatings can inadvertently provide a hydrocarbon source for microbial growth. To investigate this potential, anti-graffiti coatings were contaminated by common soil microbes through culture plate production and microbial isolate cultivation; the biodeterioration was measured with Electrochemical Impedance Spectroscopy (EIS). EIS data indicated that no coating was affected by microbes. Fourier-transform infrared spectroscopy in attenuated total reflection mode (FTIR / ATR) was used to note changes in coating chemistry before and after exposure to microbes. FTIR / ATR proved to be a more sensitive technique than EIS in detecting changes to the coatings and suggested that Blok-Guard® was susceptible to biodeterioration. Effective removal of paint and marker graffiti from the coatings was tested with water, ethanol (80% in distilled water), acetone, and a commercial product, Defacer Eraser® Graffiti Wipe. Defacer Eraser® Graffiti Wipe was more successful than other solvent systems in removing graffiti from stone coated with anti-graffiti coatings. When all the results were assessed together, Protectosil® exhibited the best results followed by Blok-Guard® and finally Fluorolink® P56.
Download: JCAC32 Tarnowski et al