Organlc coatlng Bronze Atmospheric corrosion UV degradatlon Electrochemlcal techniques XPS A 3-mercapto-propyl-trimethoxysilane coating (PropS..SH) applied on Cu-Si-Mn bronze, patinated by "liver of sulphur", was investigated as a non-toxic alternative to Incralac", usually applied on outdoor artistic bron7.eS. Electrochemical testing was performed in synthetic acid rain. Exposure to temperature/UV cycles and ac celerated corrosion test simulating unsheltered exposure to rainwater was also carried out. The exposed samples were charac terised by FEG..SEM coupled with EDS on F1B cross-sections and XPS on free surfaces. The black patina wi thout protective coating was scaroely protective against bronze corr06ion and easily transformed into cuprous oxide. PropS..SH coating fully preserved the black patina microstructure and phase constituents (c uprous oxide and cuprous sulphide). The PropS-SH coating also resulted more protective than Incralac• when aged under runoff conditions. Selective dissolution of copper from the silicon bronze alloy was observed on both uncoated and Incralac "-coated bronze, leading to the formation of an internai Si-rich corrosion layer. comerstone event in the field of cultural heritage conservation (1). Protective treatments, including both cleaning procedures and appli cation of surface coatings, such as acrylic polymers admixed with cor rosion inhibitors (Incralac •), were found to be the best solution against atmospheric corrosion (1). Incralac• was developed in 1964 by the International Copper Research Association (INCRA) (2). lt is an unpatented formulation based on Acryloid B 44, a thermoplastic methyl methacrylate • Corresponding author. copolymer manufactured by Rohm and Haas, dissolved in rather toxic solvents, like toluene and xylene (3). Incralac• also contains benzo triazole (BTA) as a copper corrosion inhibitor and chelating agent (suspecte

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Application of protective coatings is the most widely used conservation treatment for outdoor bronzes. Eco-friendly and non-hazardous coatings are currently needed for conservation of outdoor bronze monuments. To fulfil this need, the M-ERA.NET European research project B-IMPACT (Bronze-IMproved non-hazardous PAtina CoaTings) aimed at assessing the protectiveness of innovative coatings for historical and modern bronze monuments exposed outdoors. In this project, two bronze substrates (historical Cu-Sn-Zn-Pb and modern Cu-Si-Mn alloys) were artificially patinated, by acid rain solution using dropping test and by “liver of sulphur” procedure (K2S aqueous solution) to obtain black patina, respectively. Subsequently, the application of several newly developed protective coatings was carried out and their performance was investigated by preliminary electrochemical tests. In the following steps of the work, the assessment of the best-performing coatings was carried out and their performance was compared to Incralac, one of the most widely used protective coatings in conservation practice. A multi-analytical approach was adopted, considering artificial ageing (carried out in representative conditions, including exposure to rain runoff, stagnant rain and UV radiation) and metal release, as well as visual aspect (so as to include aesthetical impact among the coating selection parameters) and morphological and structural evolution of the coated surfaces due to simulated outdoor exposure. Lastly, also the health impact of selected coatings was assessed by occupational hazard tests. The removability and re-applicability of the best-performing coatings were also assessed. The best alternatives to the conventional Incralac exhibited were: (i) fluoroacrylate blended with methacryloxy-propyl-trimethoxy-silane (FA-MS) applied on patinated Cu-Sn-Zn-Pb bronze and (ii) 3-mercapto-propyl-trimethoxysilane (PropS-SH) applied on patinated Cu-Si-Mn bronze.

The effects of various drying techniques, such as air, oven, freeze, and spray drying, on the morphological, thermal, and structural behaviors of two different nanofibrillated cellulose (NFC) materials were investigated. Field emission scanning electron microscopy (FE-SEM) observations indicated an interlaced network formation of predominantly in-plane fibrillar orientation for air-and oven-dried samples, while freeze and spray drying resulted in the formation of coarse and fine powder fractions. Comparison of redispersed powders obtained by freeze and spray drying indicated that aggregation phenomena are significantly reduced in freeze-dried specimens. Rheological and sedimentation analysis revealed that the freeze-dried NFC powders are more stable than spray-dried NFC powders when redispersed in water. Aggressive dehydration processes, such as freezing or heating, significantly influence the thermal stability of the dried cellulose samples. On the contrary, the crystallinity properties of dried NFC materials are very similar regardless of the drying treatment.

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