Mechanism of Atmospheric Corrosion of Copper in the Presence of Ammonium Sulfate Particles

Abstract

The effect of the surface concentration of submicrometer ammonium sulfate (NH 4 ) 2 SO 4 dust particles on the mechanism of atmospheric corrosion of copper has been investigated at 298 K and 93% relative humidity ͑RH͒. For surface concentrations from 1 g/cm 2 to 10 mg/cm 2 , the same corrosion products are formed at relative humidities well above the critical relative humidity of (NH 4 ) 2 SO 4 . Initially, a Cu(NH 3 ) 2ϩ complex is formed. The basic copper sulfate posnjakite precipitates when its solubility product is exceeded while NH 3 evaporates. Posnjakite may be converted to antlerite or brochantite if higher amounts of (NH 4 )SO 4 particles were deposited. The basic copper sulfates then decompose at the inner interface to form Cu 2 O. With low amounts of (NH 4 ) 2 SO 4 particles, the conversion is 100%. With high amounts of particle deposits, residual copper sulfate remains on top of a Cu 2 O-layer. With increasing amounts of deposited (NH 4 ) 2 SO 4 particles on copper, the sequence of corrosion products that are formed takes more time. The mechanism proposed in earlier work for the corrosion of copper with (NH 4 ) 2 SO 4 particles in humid air is improved to explain the new experimental findings.Before 1995, essentially all laboratory studies on the atmospheric corrosion of metals were conducted using corrosive gases in concentrations that were excessively high relative to those found in the troposphere. The corrosion product films that were produced were frequently unrealistic. For example, for copper it was not possible to produce a surface layer similar to the naturally formed patina using gaseous pollutantes like SO 2 and NO 2 . [1][2][3][4][5][6][7][8][9] However, the 1930s, Vernon demonstrated that dust particles, especially dust particles consisting of ammonium sulfate, significantly influence the corrosion of copper and lead to higher corrosion rates. [10][11][12][13][14][15][16] The factors that determine the amount of ionic surface contamination relevant for atmospheric corrosion on metal surfaces was later studied by Sinclair et al. [17][18][19][20][21][22][23] The extent of ionic deposition on indoor surfaces is influenced by the concentration of dust particles in the outdoor air, the air exchange rate between indoors and outdoors, efficiency of air filtration systems, the velocity of the air, the surface area to volume ratio, the temperature of the surface, the distance between surfaces and source of particles, and the orientation of the surface. It was shown that most of the sulfur acquired by zinc and aluminum surfaces is supplied as dry deposition, and not, as previously assumed, in gaseous form from the reaction with SO 2 . It was also shown that fine particles ͑Ͻ1 m͒, produced from corrosive gases through chemical and physical processes that occur in the atmosphere, play the decisive role in the atmospheric corrosion of metals because of their higher concentration indoors ͑due to low filtration efficiencies for fine particles͒ and because of their greater content of soluble ions compare...

Electrochemical Behavior of AISI 304SS with Particulate Silica Coating in 0.1 M NaCl

“…Water from the humid environment can be absorbed onto surfaces covered with fine dust particles containing soluble salts, creating a saturated deliquescence brine layer. [1][2][3][4] Such a layer could be extremely corrosive, even to corrosion-resistant alloys (CRAs) if the temperature were high enough, due to the salt concentration and high availability of oxygen. Furthermore, it is possible that precipitates or rock particulates could act as a crevice former and cause localized corrosion of the substrate metal.…”

Characterisation of corrosion products formed on copper exposed at indoor and outdoor sites with high H2S concentrations

“…Lobnig et al reported that the binding energy of S 2p 3/2 for posnjakite is 169?9 eV. 33 For the indoors plate, no basic copper sulphates were found in the XRD pattern, as mentioned above. The peak maximum was very similar to that for CuSO 4 (168?8 eV).…”

“…28 For the outdoors plate (Fig. 2b), posnjakite (934?9 eV) 33 and brochantite (936 eV) 33 were also possible origins in addition to the cupric species. The lower binding energy component originated from cuprite and/or chalcocite because both phases were detected in the XRD patterns for both copper plates.…”

Indoor particulate matter in four Belgian heritage sites: Case studies on the deposition of dark-colored and hygroscopic particles

“…At the deliquescence relative humidity (DRH), a sudden phase transition from solid particle to a saturated where only one filter has been sampled. (Chang and Lee, 2002;Ebert et al, 2002;Hu et al, 2010;Möller, 2010;Tang and Munkelwitz, 1994;Wise et al, 2005) NaNO 3 76-80 c -d (Möller, 2010;Tang and Munkelwitz, 1994) Na 2 SO 4 82-83 e 58 (Chang and Lee, 2002;Ebert et al, 2002;Hu et al, 2010;Tang and Munkelwitz, 1994) MgCl 2 33 -(Möller, 2010) NH 4 NO 3 61-62 c b20-30 (Chang and Lee, 2002;Ebert et al, 2002;Frankenthal et al, 1993;Möller, 2010; Sanjurjo-Sánchez and Alves, 2011) (NH 4 ) 2 SO 4 80-81 31-48 (Ciobanu et al, 2010;Ebert et al, 2002;Frankenthal et al, 1993;Hu et al, 2010;Lobnig et al, 2003;Möller, 2010;Wise et al, 2005) NH 4 HSO 4 30-40 - (Frankenthal et al, 1993;Möller, 2010 b5 - (Frankenthal et al, 1993) a The given CRH is valid for PM in the atmosphere. Once deposited on a certain material, the metastable state of the supersaturated droplet can be shifted (Ebert et al, 2002).…”