| Popis: |
The effect of submicron-sized (NH[sub 4])[sub 2]SO[sub 4] particles on the corrosion of copper has been investigated in air-H[sub 2]O mixtures at 373 K and relative humidities (RH) of 65, 75, and 88%. At 65% RH, (NH[sub 4])[sub 2]SO[sub 4] particles do not affect the oxidation of copper. At 75% RH, the critical relative humidity of (NH[sub 4])[sub 2]SO[sub 4], localized formation of Cu[sub 2]O and a basic copper sulfate, brochantite [Cu[sub 4](SO[sub 4])(OH)[sub 6]] or antlerite [Cu[sub 3](SO[sub 4])(OH)[sub 4]], is observed, depending on the amount of particles deposited. At 88% RH, sufficient water is absorbed by the particles to form solution that spreads over a large surface area. A continuous thick layer of Cu[sub 2]O 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. |
Plný text