Karakterizacija in zaščita patiniranih bronov v atmosferskih pogojih

Novak, Živa (author), Gaberšček, Miran (mentor), Kosec, Tadeja (comentor)

Baker in bron ob izpostavljenosti atmosferskim pogojem ob prisotnosti vlage, kisika in korozivnih specij oksidirata. Oksidacija poteka stopenjsko. Najprej se tvori kuprit, Cu2O, ta pa se ob dolgotrajni izpostavljenosti atmosferskim pogojem nadalje oksidira. Pri tem se tvorijo zeleni Cu(II) produkti. Za vzdrževanje stanja in izgleda se bronaste površine, izpostavljene atmosferskim pogojem, lahko zaščiti. V magistrskem delu smo spremljali nastanek korozijskih produktov na različno patiniranih (nezaščitenih) bronih in jih primerjali s korozijskimi produkti brona. Preverili in ovrednotili smo novo razvito fluoropolimerno (FA-MS) zaščito za patinirane površine. Poleg tega smo preverjali obstojnost komercialno uporabljene zaščite v restavratorski praksi in jo primerjali z novo razvitim premazom FA-MS. Tri nezaščitene bronaste vzorce (ne-patiniran, sulfidno patiniran in kloridno patiniran) smo za 4 mesece izpostavili v simulirani ljubljanski deževnici. Nastale korozijske produkte smo opazovali in okarakterizirali s pomočjo SEM/EDS, ramanske in XRD analize. Elektrokemijsko obnašanje posameznega nezaščitenega in zaščitenega (FA-MS ali Incralac) vzorca ter njihove učinkovitosti smo določili s pomočjo elektrokemijskih meritev. Lastnosti zaščite smo dodatno ovrednotili z meritvami kontaktnega kota, z AFM analizo in meritvami spremembe barve po nanosu zaščite, mehanizem vezave pa ugotavljali s pomočjo XPS analize. Učinkovitost FA-MS zaščite je na bronu in sulfidno-patiniranem bronu primerljiva z učinkovitostjo Incralac zaščite (~ 99 %), medtem ko je pri kloridno-patiniranem bronu nižja, pri 71 %. Kljub dobri učinkovitosti smo slabo obstojnost Incralac zaščite ugotovili že po 1 mesecu izpostavitve v umetno pripravljeni ljubljanski deževnici. Hidrofobnost FA-MS zaščitenih vzorcev se poveča na račun fluoroakrilatne komponente v premazu. Z XPS analizo smo ugotovili, da se po nanosu FA komponenta orientira na površino in veže na MS preko siloksanske vezi, medtem ko je MS orientirana med FA komponento in preko silanolnih skupin na substrat.

• Language: Slovenian
• Keywords: bron, patinacija, zaščita, ramanska analiza, elektrokemija
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2022
• PID: 20.500.12556/RUL-142003
• COBISS.SI-ID: 134264067
• Publication date in RUL: 14.10.2022

Secondary language

• Language: English
• Title: Characterization and protection of patinated bronzes in atmospheric conditions

Abstract

Copper and bronze oxidise when exposed to atmospheric conditions in the presence of moisture, oxygen, and corrosive species. Oxidation takes place in stages, where cuprite, Cu2O, forms first and is then further oxidised upon long-term exposure. In this process, green Cu(II) products are formed. To maintain condition and appearance, bronze surfaces exposed to atmospheric conditions can be protected. In this master's thesis, we monitored the formation of corrosion products on different (unprotected) patinated bronzes and compared them with corrosion products formed on bronze. We checked and evaluated the newly developed fluoropolymer (FA-MS) protection for patinated surfaces. In addition, we studied the durability of the commercially used protection in restorative practice and compared it with the newly developed FA-MS coating. Three unprotected bronze samples (non-patinated, sulphide-patinated and chloride-patinated) were exposed for 4 months in simulated Ljubljana rainwater. Corrosion products were observed and characterized using SEM/EDS, Raman and XRD analysis. The electrochemical behaviour of unprotected and protected (FA-MS or Incralac) samples and their efficiencies were determined by means of electrochemical measurements. The properties of the protection were additionally evaluated with contact angle measurements, AFM analysis and colour change analysis after the addition of protection, also the binding mechanism was determined with the help of XPS analysis. The efficiency of FA-MS protection on bronze and sulphide-patinated bronze is comparable to that of Incralac protection (~ 99 %), while it is lower on chloride-patinated bronze, at 71 %. Despite the good efficiency, the poor stability of Incralac protection was confirmed after only 1 month of exposure in artificially prepared Ljubljana rainwater. Hydrophobicity of FA-MS protection system is increased due to fluoroacrylate component in the coating. XPS analysis revealed that the FA component is oriented on the surface and binds to the MS via siloxane bonds, while the MS is oriented between the FA component and via the silanol groups on the substrate.

• Keywords: bronze, patination, protection, Raman analysis, electrochemistry