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

• Autores: Morales, J.; Fernandez, G. T.; Gonzales, S.; Esparza, P.; Salvarezza, Roberto Carlos; Arvia, Alejandro Jorge
• Año de publicación: 1998
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Ciencias Exactas; Química; A. brass; C. passive films; C. localized corrosion
• Institución: Universidad Nacional de La Plata

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_NaCl) in the temperature range 5 °C ≤ T ≤ 45 °C were studied comparatively by potential sweeping at 2 × 10⁻²Vs⁻¹ and 2 × 10⁻⁴Vs⁻¹ and de-alloying measurements. The passivation of α-brass and β-brass was related to the electroformation of a complex ZnO · xH²O/Cu<²O 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_b) was exceeded. At constant temperature, the value of E_b shifted negatively as either cNaCl or the zinc content in the alloy was increased. For β-brass, the value of E_b 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_b 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.
Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas