DIAGRAMA DE POURBAIX PDF

La presencia de agentes complejantes, como por ejemplo, cloruros, bromuros, cianuros, amoniaco, carbonatos, etc. Como consecuencia, en los diagramas aparecen nuevos dominios para las especies inicas en disolucin que ocupan espacios ms amplios que los correspondientes a los sistemas metal-agua. Tambin se puede observar que las lneas aparecen representadas en el diagrama con dos tipos de trazado: continuo y discontinuo fino. Si aparecen con trazado continuo indican un equilibrio bien entre dos especies slidas o bien entre una especie slida y una especie soluble. Si aparecen con trazado discontinuo fino indican un equilibrio entre dos especies solubles. Las dos lneas discontinuas gruesas sealadas como a y b, que representan el equilibrio de descomposicin del agua con desprendimiento de oxgeno e hidrgeno, respectivamente.

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On either side of the line, one form of the species will instead be said to be predominant. Usually, the activity of a species is approximated as equal to the concentration for soluble species or partial pressure for gases.

The same values should be used for all species present in the system. Sometimes additional lines are drawn for other concentrations.

For instance, carbonate has a great effect upon the diagram for uranium. See diagrams at right. The presence of trace amounts of certain species such as chloride ions can also greatly affect the stability of certain species by destroying passivating layers. In addition, changes in temperature and concentration of solvated ions in solution will shift the equilibrium lines in accordance with the Nernst equation.

The diagrams also do not take kinetic effects into account, meaning that species shown as unstable might not react to any significant degree in practice. A simplified Pourbaix diagram indicates regions of "immunity", "corrosion" and "passivity", instead of the stable species.

They thus give a guide to the stability of a particular metal in a specific environment. Immunity means that the metal is not attacked, while corrosion shows that general attack will occur.

Passivation occurs when the metal forms a stable coating of an oxide or other salt on its surface, the best example being the relative stability of aluminium because of the alumina layer formed on its surface when exposed to air.

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Pourbaix diagram

On either side of the line, one form of the species will instead be said to be predominant. Usually, the activity of a species is approximated as equal to the concentration for soluble species or partial pressure for gases. The same values should be used for all species present in the system. Sometimes additional lines are drawn for other concentrations. For instance, carbonate has a great effect upon the diagram for uranium. See diagrams at right. The presence of trace amounts of certain species such as chloride ions can also greatly affect the stability of certain species by destroying passivating layers.

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Diagrama de Pourbaix

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