Fluorinated phosphoric ester-based protective material for limestone-made ancient monuments, buildings, and artifacts: an X-ray photoelectron spectroscopy study

In this study, fluorinated phosphoric eaters are evaluated as protective ma terial for limestone from water-driven alteration processes. Hypotheses as to their molecular arrangement are also provided. The surface composition o f limestone after treatment with a commercially available fluorinated phosp horic ester material was evaluated by X-ray photoelectron spectroscopy (XPS ). Results were then compared with those obtained for the treated limestone after accelerated aging tests. In the limestone that had not been subjecte d to aging processes an XPS determined thickness of the protective coating equivalent to 95 +/- 18 Angstrom was observed. This fell to 49 +/- 10 Angst rom in the limestone examined after intensive aging tests. However, low sur face wettability (theta = 135 degrees +/- 4) was seen to be maintained.