Hydroxyapatite (HAP) based treatments have been proposed for the protection of marble artifacts against acidic rain corrosion, because of the much lower dissolution rate and solubility of HAP with respect to calcite. Results obtained so far are promising, but optimization is necessary to make the treated layer complete, non-cracked and non-porous. In this study, ethanol additions were proposed to enhance surface coverage while avoiding formation of cracks, thus increasing the acid attack resistance of the substrate. The investigation of the best formulation and treating procedure to be used was determined on powders, then the acid resistance of the most promising treatments was evaluated on coarse Carrara marble specimens by a specifically designed simulated rain apparatus, allowing to drop a continuous flux of acidic solution onto the samples, thus being closer to real weathering conditions on site. Results obtained show that HAP is a valuable option for marble protection, being able to slow down marble decay due to acid rain and exhibiting a better performance than ammonium oxalate, currently the most investigated inorganic protective for marble.
Marble protection by hydroxyapatite coatings / Gabriela Graziani; Enrico Sassoni; Elisa Franzoni; George W. Scherer. - STAMPA. - 2:(2016), pp. 803-810. (Intervento presentato al convegno 13th International Congress on the Deterioration and Conservation of Stone tenutosi a Paisley (UK) nel 6-10 September 2016).
Marble protection by hydroxyapatite coatings
GRAZIANI, GABRIELA;SASSONI, ENRICO;FRANZONI, ELISA;
2016
Abstract
Hydroxyapatite (HAP) based treatments have been proposed for the protection of marble artifacts against acidic rain corrosion, because of the much lower dissolution rate and solubility of HAP with respect to calcite. Results obtained so far are promising, but optimization is necessary to make the treated layer complete, non-cracked and non-porous. In this study, ethanol additions were proposed to enhance surface coverage while avoiding formation of cracks, thus increasing the acid attack resistance of the substrate. The investigation of the best formulation and treating procedure to be used was determined on powders, then the acid resistance of the most promising treatments was evaluated on coarse Carrara marble specimens by a specifically designed simulated rain apparatus, allowing to drop a continuous flux of acidic solution onto the samples, thus being closer to real weathering conditions on site. Results obtained show that HAP is a valuable option for marble protection, being able to slow down marble decay due to acid rain and exhibiting a better performance than ammonium oxalate, currently the most investigated inorganic protective for marble.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
