Corrosion process of silver in environments containing 0.1 ppm H₂S and 1.2 ppm NO₂

Abstract

The effects of sub-ppm levels of nitrogen dioxide and hydrogen sulfide, and the adsorbed water on the corrosion of silver were studied in order to get a better understanding of the atmospheric corrosion process. An in situ mass balance was taken to monitor the kinetic behavior and the surface and the corrosion film were analyzed by X-ray photoelectron spectroscopy (XPS).In H 2 S environments, the tarnish film consisted of silver sulfide, and the corrosion rate depended upon oxygen as well as relative humidity. Silver was oxidized by only oxygen and the corrosion behavior conformed to a type of a parabolic law. In NO 2 environments, the corrosion film consisted of nitrate and oxide, and the corrosion rate depended upon oxygen as well as relative humidity. Compared to hydrogen sulfide, the formation of silver nitrate being strong hydroscopic reduced the effect of humidity on corrosion rate. In H 2 S þ NO 2 environment, the corrosion process was independent of both oxygen and humidity, and the kinetic behavior conformed to a linear law. The difference of corrosion process between H 2 S or NO 2 environments and H 2 S þ NO 2 environments is thought to be due to the role of nitrogen dioxide as an ionic conductor and the presence of strong oxidizing species such as elemental sulfur which can be produced from the following reaction: H 2 S þ 2NO 2 ! S þ 2HNO 2 . In addition, the role of adsorbed water affecting atmospheric corrosion process was mentioned based on the amount of adsorbed water from the three types of exposure environments.Um ein besseres Verstândnis der atmosphârischen Korrosionsprozesse von Silber zu bekommen, wurden der Einfluss von ppm-Gehalten an Stickstoffdioxid und Schwefelwasserstoff sowie von adsorbiertem Wasser auf die Korrosion von Silber untersucht. Eine in-situ Massenwaage wurde eingesetzt, um das kinetische Verhalten zu kontrollieren. Die Oberfläche und der Korrosionsfilm wurden mittels Röntgenphotoelektronenspektroskopie (XPS) analysiert.In H 2 S-Umgebungen bestand der Anlauffilm aus Silbersulfid und die Korrosionsgeschwindigkeit hing sowohl vom Sauerstoff als auch von der relativen Feuchtigkeit ab. Silber wurde nur durch Sauerstoff oxidiert und das Korrosionsverhalten stimmte mit einem parabolischen Zeitgesetz überein. In NO 2 -Umgebungen bestand der Korrosionsfilm aus Nitrat und Oxid und die Korrosionsgeschwindigkeit hing sowohl vom Sauerstoff als auch von der relativen Feuchtigkeit ab. Verglichen mit Schwefelwasserstoff führte die Bildung von stark hydroskopischem Silbernitrat zu einer Verringerung des Einflusses der Feuchtigkeit auf die Korrosionsgeschwindigkeit. In H 2 S þ NO 2 -Umgebung war der Korrosionsprozess unabhängig von Sauerstoff und Feuchtigkeit und das kinetische Verhalten entsprach einem linearen Zeitgesetz. Es wird angenommen, dass die Unterschiede im Korrosionsprozess zwischen H 2 S-, NO 2 -und H 2 S þ NO 2 -Umgebungen durch die Rolle des Stickstoffdioxids als ionischer Leiter und durch die Anwesenheit von stark oxidierenden Spezies wie elementarer Schwefel, der durch die fo...

The Influence of Gaseous Pollutants on Silver Artifacts Tarnishing

“…exposure were identified only one product (AgNO 3 ) from nitrates anions as corrosion products on silver surface, Therefore this compound was expected of NO 2 gas, but analysis showed Silver ammine nitrate (Ag(NO 3 ) 3 (NO) 3 ).…”

“…Previous lab exposure tests often focused on silver tarnish due to Sulphur containing pollutants [2]- [7]. These studies have been agreed in their results which can be summarized in the formation of silver tarnish as black layer consisting of Ag 2 S as major corrosion product and Ag 2 SO 4 in a negligible quantity.…”

“…Results of Previous studies indicated that nitrogen dioxide is not considered a corrosion factor of silver because silver does not react with it, but it only acts as an accelerated factor of silver tarnish with other gases [8] [9] [10] [11] [12] even though Previous study found silver nitrate Ag 2 NO 3 as corrosion products on exposed silver to 1.2 ppm NO 2 for 40 hours [2].…”

A reaction study of sulfur vapor with silver and silver–indium solid solution as a tarnishing test method

“…Several experiments, using various corrosive gases, such as sulfur vapor [6], hydrogen sulfide [7], sulfur dioxide [8], and organic sulfur [9], have been performed to see the influence on the rate of silver tarnishing. Other environmental parameters, such as temperature, relative humidity [10], illumination [8], and silver surface state [11], have also been studied to explore the silver tarnishing mechanism, thereby searching possible scientific and engineering solutions for anti-tarnishing purposes.…”

The sulfidation process of sterling silver in different corrosive environments: impact of the process on the surface films formed and consequences for the conservation-restoration community

“…The numerous analyses conducted over decades about corrosion rate, underlying mechanisms and the subsequently formed corrosion products, demonstrate that the corrosion process of silver alloys is affected by several parameters such as temperature, moist content, concentration of H 2 S [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Compared to pure silver, alloys have several additional properties (e.g.…”