The Effect of Submicron Ammonium Sulfate Particles on the Corrosion of Copper

Abstract

The effect of submicron-sized (NH4)2SQ particles on the corrosion of copper has been investigated in air-H20 mixtures at 373 K and relative humidities (RH) of 65, 75, and 88%. At 65% RH, (NH~)2SO4 particles do not affect the oxidation of copper. At 75 % RH, the "critical relative humidity" of (NH4)2SO4, localized formation of Cu20 and a basic copper sulfate, brochantite [Cu4(SO4)(OH)6] or antlerite [Cu~(SO~)(OH)4], isobserved, depending on the amount of particles deposited. At 88% RH, sufficient water is absorbed by the particles to form a solution that spreads over a large surface area. A continuous thick layer of Cu20 forms rapidly and becomes overgrown by antlerite crystals. Beneath the oxide scale, the copper substrate is locally corroded. The present work clearly demonstrates that ammonium sulfate particles, which are a major constituent of urban atmospheric dust, are an important factor in the formation of patina on copper.

Corrosion mechanism of copper immersed in ammonium sulfate solution

“…R ct , representing the difficulty of charge transfer, could give some information about the corrosion resistance. The R ct of copper sample after 7 days of immersion is the highest one among these samples, which is consistent with the corrosion current extrapolated by polarization curves in Copper immersed in (NH 4 ) 2 SO 4 solution usually undergoes anodic dissolution to generate Cu + ions, [1,[13][14][15][16] which will react with ammonia derived from the hydrolysis of ammonium ions to generate [Cu(NH 3 ) n ] + . However, Cu + and [Cu(NH 3 ) n ] + ions can be rapidly oxidized to Cu 2+ and [Cu(NH 3 ) n ] 2+ ions under aerobic conditions.…”

“…One of the common salt particles within the rural and industrial atmosphere is (NH 4 ) 2 SO 4 , which would be dissolved to form a thin (NH 4 ) 2 SO 4 solution layer on copper surface when the ambient humidity gets greater than the critical relative humidity of (NH 4 ) 2 SO 4 and consequently gives rise to the corrosion of copper. [1,[13][14][15][16] Especially, haze is very serious in winter in northern China, and (NH 4 ) 2 SO 4 is one of the main pollutants in haze, which causes serious corrosion of metallic materials. [17,18] It was reported that the corrosion behavior is quite similar to that in the bulky (NH 4 ) 2 SO 4 solution when the electrolyte film thickness on the metal surface reaches 20-30 molecular layer thickness.…”

“…However, the copper would be corroded by some polluted gases and salt particulates after exposure in the ambient atmosphere, which can reduce its service life. One of the common salt particles within the rural and industrial atmosphere is (NH 4 ) 2 SO 4 , which would be dissolved to form a thin (NH 4 ) 2 SO 4 solution layer on copper surface when the ambient humidity gets greater than the critical relative humidity of (NH 4 ) 2 SO 4 and consequently gives rise to the corrosion of copper . Especially, haze is very serious in winter in northern China, and (NH 4 ) 2 SO 4 is one of the main pollutants in haze, which causes serious corrosion of metallic materials …”

Copper and Copper Alloys

“…Basic copper chloride and carbonate are also found [180][181][182][183][184]. The mechanism of basic copper sulfate formation has been the subject of several studies that have been reviewed [183,184].…”

“…The effect of submicron (NH 4 ) 2 SO 4 particles on the corrosion of copper at varying relative humidities (RHs) and-temperatures was studied by Lobnig et al [180,181], who showed that (NH 4 ) 2 SO 4 particles lead to the corrosion products found in natural patinas. In a recent study [189], it was investigated whether NH 4 HSO 4 and (NH 4 ) 3 H(SO 4 ) 2 may be responsible for formation of basic copper sulfate in the naturally formed patina on copper during atmospheric corrosion.…”