In this essay, results regarding the experimental use of sodium fluoride on decaying limestone rock are presented; previous treatments have required a great amount of time and resources to be invested. Samples, where the sodium fluoride was applied, are part of a cornice found at the archaeological zone of the Rio Bec, in the town of Calakmul in Campeche. The composition of the rock, its deterioration and physical properties were studied by different analytical techniques (Scanning Electron Microscopy – SEM, petrography, Energy dispersive X-ray spectroscopy – EDS, X-Ray diffraction – XRD, among others), in order to compare to the samples treated. With a low quantity of sodium fluoride and few applications, an improvement of the physical properties of the rock was achieved as well as the conversion of calcium carbonate into calcium fluoride, a much more stable compound in the face of weathering. The sodium fluoride acts by ion exchange, re-mineralizing the structure of the rock. The objective of this work is to ponder upon the use of this compound for in situ treatments.