Efficacy of zinc salts to protect glass against atmospheric alteration. Part I: Effects of a spraying treatment

Abstract

Following an industrial process to protect manufactured glass windows against atmospheric corrosion during their storage and transport, this research is focused on the possibility that a surface deposit of a small amount of zinc salts may efficiently reduce the atmospheric alteration kinetics of ancient glasses (soda, potash, and mixed alkali silicates). To this end, the chemical action of zinc salts was investigated by means of aging experiments (with temperature and relative humidity (RH) control) on three glass models, of which compositions are representative of the cultural heritage. When the treatment was performed on pristine glass (about 1 μg/cm2 of deposited Zn2+ ions), treated glass plates developed a significantly thinner hydrated layer than the untreated ones at 80°C or at 40°C (85 RH%). The formation of alkali and Ca‐carbonates salts on the surface was also considerably reduced. The state of the glass surface undergoing the Zn treatment and the temperature of the treatment seem critical regarding the efficacy of the protection.

Efficacy of zinc salts to protect glass against atmospheric alteration. Part II: Possible passivation mechanisms

“…The decrease of the surface density of Na‐carbonates with the spraying treatment is directly linked to the reduction of the hydrated layer thickness. This reduction was more pronounced with the ZP_1.5 treatment than with the ZP_0.1 treatment (see part I of this study 16 ). For the ZN_0.1 treatment as well, a significant reduction of the global hydration level was highlighted by FTIR experiments in transmission mode in the region associated to the absorbance of the –OH groups at 3700‐2500 cm −1 after aging at 80°C, 85 RH%, for a 1‐day period (orange curve as compared to the red curve associated to the untreated glass in Figure 6).…”

“…With the spraying treatment, the concentration of Zn 2+ ions on the glass surface was evaluated at 1.5 ± 0.1 μg/cm 2 for the highest concentration and at 0.1 ± 0.03 μg/cm 2 for the lowest concentration. They correspond respectively to the ZP_1.5 and ZP_0.1 treatment already described in part I of this study 16 . With the immersion treatment, the concentration of deposited Zn 2+ was evaluated very close to the one with the spraying treatment of lowest concentration (0.1 ± 0.03 μg/cm 2 ), and is named ZN_0.1 .…”

“…The hydration levels were compared for the different aged glass plates using Fourier‐Transform InfraRed (FTIR) spectroscopy in transmission mode. Details about the operating conditions are given in part I of this study ( 16 —Supplemental Materials, Section S2.1).…”

“…2.1 | Zn(II) deposits on glass surface Two types of treatments are studied in this paper. The first one is the spraying treatment described in part I of this study 16 (treatment at ambient temperature) and considered for the protection of ancient glass objects under the museum atmosphere. The second one is treatment by immersion in hot zinc salt solution, which was investigated for comparison purposes with the first one to better understand the origin of the zinc protective effect.…”

“…Another situation where zinc salts have proven successful as glass corrosion inhibitors is described in the part I of this study, 16 namely the atmospheric alteration of glass in unsaturated humidity (relative humidity [RH] < 100°C) in conditions excluding liquid water condensation on the surface. The treatment consists in spraying a zinc salts‐bearing alcoholic solution on the glass surface.…”