Lanthanum-Silica Sol-Gel Coatings for Protecting Metallic Materials in Museums: Approaches to Copper, Bronze, Lead and Steel

Museum objects made from metals face the challenge of delaying corrosion in exhibition rooms, showcases and holdings. This study examined some innovative solutions used to protect such items based on sol-gel coatings doped with lanthanum. These coatings were prepared from sols based on TEOS as a precursor. Lanthanum acetate/nitrate was added as a doping agent and corrosion inhibitor. The coatings were deposited upon slabs of copper, bronze, lead and steel, since they are among the most common metals present in museums items. The coatings application was accomplished by immersion-extraction, and the remaining sols were gelled and characterized by Fourier transformed infrared spectroscopy and differential thermal analysis and thermogravimetry. To evaluate the behaviour and resistance of the coatings, tests of accelerated aging were carried out in climatic and Kesternich chambers, as well as under an atmosphere saturated with organic acids and under UV irradiation. The simulated conditions tested were undertaken to approach real conditions inside a conventional museum showcase. The microstructure of the coatings before and after accelerated aging tests was observed through optical and field emission scanning electron microscopies. The results indicated that these coatings can be a useful preventive, conservation avenue to protect copper, bronze and lead items exhibited in museums.

[1]  Chun-shan Che,et al.  Preparation and Corrosion Performance of Lanthanum Nitrate Conversion Coating on Hot-dip Galfan Steel , 2016 .

[2]  R. B. Figueira,et al.  Hybrid sol-gel coatings: Smart and green materials for corrosion mitigation , 2016 .

[3]  E. Franzoni,et al.  TEOS-based treatments for stone consolidation: acceleration of hydrolysis–condensation reactions by poulticing , 2015, Journal of Sol-Gel Science and Technology.

[4]  M. Blanco-Varela,et al.  Interaction of TEOS with cementitious materials: Chemical and physical effects , 2015 .

[5]  Herbert Hutter,et al.  Sol–gel silica coating for potash–lime–silica stained glass: Applicability and protective effect , 2014 .

[6]  R. B. Figueira,et al.  Organic–inorganic hybrid sol–gel coatings for metal corrosion protection: a review of recent progress , 2014, Journal of Coatings Technology and Research.

[7]  F. Zucchi.  Sol-gel coatings for the preservation of metallic heritage artefacts , 2013 .

[8]  M. A. García,et al.  Silica doped with lanthanum sol–gel thin films for corrosion protection , 2012 .

[9]  Zhicong Shi,et al.  Studies of the Conversion Coatings Formed by Combined Use of Lanthanum Salt and Benzotriazole on Commercial Brass , 2011 .

[10]  C. A. Anjinho,et al.  Studies on polymeric conservation treatments of ceramic tiles with Paraloid B‐72 and two alkoxysilanes , 2010 .

[11]  G. Wheeler,et al.  Effect of the addition of hydroxyl-terminated polydimethylsiloxane to TEOS-based stone consolidants , 2010 .

[12]  M. Mosquera,et al.  Surfactant-synthesized ormosils with application to stone restoration. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[13]  车淳山,et al.  Study on lanthanum salt conversion coating modified with citric acid on hot dip galvanized steel , 2010 .

[14]  M. Mosquera,et al.  New Nanomaterials for Protecting and Consolidating Stone , 2009 .

[15]  Gordon P. Bierwagen,et al.  Sol–gel coatings on metals for corrosion protection , 2009 .

[16]  M. Zheludkevich,et al.  Lanthanide Salts as Corrosion Inhibitors for AA5083. Mechanism and Efficiency of Corrosion Inhibition , 2008 .

[17]  R. Bertoncello,et al.  Sol–gel silica coatings for the protection of cultural heritage glass , 2008 .

[18]  Enrique Julve Salvadó.  Un fenómeno corrosivo deseable: la atractiva pátina verde de los edificios nórdicos y centroeuropeos , 2006 .

[19]  Manuel García-Heras,et al.  Preparation and electrochemical study of cerium-silica sol-gel thin films , 2004 .

[20]  M. Montemor,et al.  Corrosion performance of a two‐step pre‐treatment for galvanized steel based on lanthanum nitrate and silanes , 2004 .

[21]  J. Tétreault,et al.  Corrosion of Copper and Lead by Formaldehyde, Formic and Acetic Acid Vapours , 2003 .

[22]  A. Abrão,et al.  Synthesis and characterization of lanthanum acetate for application as a catalyst , 2002 .

[23]  B. Dumont,et al.  Hybrid Sol–gel Clear Coatings for Decoration Brass Profiles , 2001 .

[24]  M. Arenas,et al.  Inhibition of 5083 aluminium alloy and galvanised steel by lanthanide salts , 2001 .

[25]  M. García.  Influencia de las condiciones de preparación en la luminiscencia de recubrimientos de sílice pura , 2000 .

[26]  Daniel de la Fuente,et al.  Corrosión atmosférica de metales en condiciones climáticas extremas , 2000 .

[27]  G. C. Allen,et al.  Nature of Lead Patination , 1999 .

[28]  J. Calvino,et al.  Lanthanide compounds as environmentally-friendly corrosion inhibitors of aluminium alloys : A review , 1998 .

[29]  M. Marcos,et al.  Protection against corrosion in marine environments of AA5083 Al–Mg alloy by lanthanide chlorides , 1997 .

[30]  M. Vannice,et al.  Influence of Pretreatment on Lanthanum Nitrate, Carbonate, and Oxide Powders , 1996 .

[31]  P. C. Hess,et al.  Vibrational spectra of high-silica glasses of the system K2OSiO2La2O3 , 1991 .

[32]  J. Bünzli,et al.  Vibrational Spectra of Anhydrous Lanthanum, Europium, Gadolinium, and Dysprosium Nitrates and Oxinitrates , 1978 .

[33]  D. A. Edwards,et al.  Transition metal acetates , 1968 .

[34]  C. Rao,et al.  Infrared spectra and thermal decompositions of metal acetates and dicarboxylates , 1968 .