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 esters are evaluated as protective material for limestone from water-driven alteration processes. Hypotheses as to their molecular arrangement are also provided. The surface composition of limestone after treatment with a commercially available fluorinated phosphoric 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 subjected to aging processes an XPS determined thickness of the protective coating equivalent to 95 +/- 18 Angstrom was observed. This fell to 49 +/- 10 Angstrom in the limestone examined after intensive aging tests. However, low surface wettability (theta = 135 degrees +/- 4) was seen to be maintained.