article posted 21 March 2016
Dr Dagmar Galusková has been working in the area of the silicate chemistry predominantly on the chemical durability of glasses and corrosion resistance of the structural ceramics since 2004. In 2010 she earned her PhD at the Institute of Inorganic Chemistry at the Slovak Academy of Sciences in Bratislava. She is responsible for the chemical analysis, both mass spectrometry and atomic emission spectroscopy using ICP instruments and method development applied for the material characterization in respect to its corrosion resistance. She gained experiences in studying the mechanisms of corrosion of the structural ceramics, polymer derived ceramics (the study stay in Darmstadt University of Technology) as well ceramics for dental applications. Her present scientific interest include the anticorrosive layers developed for metal protection as well corrosion of the historical artefacts especially glasses.
Corrosion Of Metal/Glass Joints In Acetic Acid Vapours
Dagmar Galusková*, Alexandra Nowicka, Dušan Galusek
1Joint Glass Centre of the IIC SAS, TnU AD, and FChPT STU, Trencín, Slovakia
The mechanism of corrosion of glass and metal is well known, but it is worth to pay attention to the glass/metal connections. The deterioration of ancient and historic glass/metal joints within museum collection results in visual alteration and physical damages . Historical objects are exposed to different corrosion agents occurring in museum environment. Temperature and relative humidity (RH) variations, gaseous and particulate pollution all play an important role in deterioration of museum objects . Acetic acid is major corrosive pollutant in indoor cultural heritage premises. In particular acetic acid is known to be emitted from all natural woods with hardwoods, e.g. oak, being thought to emit the highest concentrations of acetic acid. The source of acetic acid is, in part, due to the hydrolysis of acetyl group esters in the hemicellulose, which constitutes roughly one-third of total carbohydrates in the wood . Acetic acid with appearance of high relative humidity causes corrosion of historical objects such as glass, metals and their joints. Corroding glass forms alkaline surface films, which may lead to the metal corrosion products in the contact zone, for example different sodium copper carbonates. Most of the corrosion products in glass/metal connection remain unspecified as yet .
The aim of this work was investigation of corrosion resistance of glass/metal joints in contact with the acidic vapour simulating environmental museum condition (collections including jewellery or other glassy historical objects). A specimen of glass with high content of alkaline elements covered with a copper tape were corroded in vapours generated from the solution containing 50 % of the acetic acid. The composition of high alkaline glass (in wt%: 73.94 SiO2
; 14.48 K2
O; 9.26 CaO; 0.84 Na2
O; 0.64 B2
; 0.59 MgO; <0.1 BaO; PbO; Al2O3; Fe2
) is similar to a glass dated to the 18th century, which is part of the collection of the National Museum in Cracow . Two environmental conditions were applied: constant temperature and relative humidity and night/day cycle mode.
In the area of the metal/glass joint traped acetic vapours accumulated, and changed the corrosion environment into more concentrated with respect to the content of acetate ions. Additionally corrosion effect was enhanced by leaching of alkalies from the glassy surface. Changing of conditions from acidic to alkaline often results in attack on the silica network itself. Near the contact zone between copper and glass were observed deposits of the corrosion product. The copper based crystalline phase was detected in the area where metal was connected to the glass (Fig 1 a and b).
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