engleski

Efficiency of applying ammonium oxalate for protection of monumental limestone by poultice, immersion and brushing methods

Samples of cretaceous limestone have been treated with three application methods (poultice, immersion and brushing) using different concentrations of ammonium oxalate solution (AmOx) and varying treatment time in order to test the efficiency of surface and in-depth formation of a protective layer of calcium oxalate (CaOx). Synchrotron-based microanalytical techniques (SR- μXRD with 12.5 μm×7.5 μm (H ×V ) probe size, SR- μFTIR with 10 μm × 10 μm and 8 μm × 20 μm probe sizes) and laboratory μFTIR, XRD and SEM have been employed for analysis of the treated samples. Synchrotron-based techniques showed variations in the CaOx distribution along the surface on a micrometer scale. All treatments resulted in the development of a CaOx layer with a maximum thickness of approximately 40 μm. Application by the brushing method with 10 1-min applications with 5-min breaks during one hour showed a development of the calcium oxalate layer equivalent to the poultice treatment taking 10 h. This treatment could be preferred for large marble or limestone surfaces where poultice usage is economically not feasible

ammonium oxalate ; calcium oxalate ; synchrotron ; micro X-ray powder diffraction ; micro FTIR spectroscopy

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