Corrosion behaviour of tantalum in sodium hydroxide solutions |
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Authors: | A Robin |
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Affiliation: | (1) Departamento de Engenharia de Materiais, Faculdade de Engenharia Química de Lorena, Polo Urbo-Industrial, Gleba AI-6, 12600-000 Lorena, SP, Brazil |
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Abstract: | The corrosion behaviour of tantalum has been investigated in sodium hydroxide solutions at different temperatures, using open-circuit potential measurements, potentiodynamic polarization, polarization resistance method and electrochemical impedance spectroscopy. Tantalum showed a passive behaviour in 5 and 10 wt % NaOH at 25, 50 and 75 °C, and in 15 wt % NaOH at 25 and 50 °C. In 15 wt % NaOH at 75 °C and in 30 wt % NaOH at all temperatures, tantalum presented a passive–active transition (self-activation) due to the spontaneous dissolution of its superficial air-formed oxide, and afterwards remained in the active state for long times, forming a polytantalate compound. In all cases, the corrosion rates increase with increasing NaOH concentration and temperature. |
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Keywords: | corrosion passivation sodium hydroxide tantalum |
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