A comparative study of the passivation and localized corrosion of α-brass and β-brass in borate buffer solutions containing sodium chloride : III. The effect of temperature
The passivation and localized corrosion of α-brass and β-brass in an aqueous borate-boric acid buffer (pH 9) containing different concentrations of NaCl (c<sub>NaCl</sub>) in the temperature range 5 °C ≤ T ≤ 45 °C were studied comparatively by potential sweeping at 2 × 10<sup>−2<...
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| Autores principales: | , , , , , |
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| Formato: | Articulo |
| Lenguaje: | Inglés |
| Publicado: |
1998
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| Materias: | |
| Acceso en línea: | http://sedici.unlp.edu.ar/handle/10915/118441 |
| Aporte de: |
| Sumario: | The passivation and localized corrosion of α-brass and β-brass in an aqueous borate-boric acid buffer (pH 9) containing different concentrations of NaCl (c<sub>NaCl</sub>) in the temperature range 5 °C ≤ T ≤ 45 °C were studied comparatively by potential sweeping at 2 × 10<sup>−2</sup>Vs<sup>−1</sup> and 2 × 10<sup>−4</sup>Vs<sup>−1</sup> and de-alloying measurements. The passivation of α-brass and β-brass was related to the electroformation of a complex ZnO · xH<sup>2</sup>O/Cu<<sup>2</sup>O layer, its thickness and compactness presumably increasing with temperature. For both α-brass and β-brass immersed in an aqueous NaCl-containing buffer, pitting corrosion was observed as the value of the breakdown potential (E<sub>b</sub>) was exceeded. At constant temperature, the value of E<sub>b</sub> shifted negatively as either cNaCl or the zinc content in the alloy was increased. For β-brass, the value of E<sub>b</sub> decreased slightly with increasing temperature in the range 5 °C≤ T ≤45 °C. In the range 5 °C≤ T ≤ 25 °C, for α-brass the value of E<sub>b</sub> was close to that reported for copper, whereas for T > 25 °C it approached those values measured for β-brass. De-alloying measurements in aqueous 0.5 M NaCl indicate that zinc surface enrichment of α-brass was responsible for the decrease in pitting corrosion resistance at T > 45 °C. |
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