Efeito da adição de niobio na formação e estabilidade de filmes de oxidos superficiais de aços inoxidaveis de baixo teor de carbono

AUTOR(ES)
DATA DE PUBLICAÇÃO

1984

RESUMO

The effect of high level Niobium additions (up to 2 weight per cent) in the formation and stability of superficial oxide films grown on low carbon stainless steels was studied. A physical model is proposed to explain the oxide films growth, take into account the superficial free energy distribution on the polycrystalline solid electrode. This model allows the calculation of the charge transfer coefficient and interfacial metal-film current density and the evaluation of the Niobium effect on these parameters. It was analysed the Niobium influence in the beginning of the transpassivity region with respect of the superficial oxide semiconductor characteristic changes. After the transpassivity region a second passivity and a second transpassivity region occur simultaneously with oxygen evolution. In these regions the superficial oxide films transformations are potential and sweep velocities dependent. For low velocities (v = 20 mV/s) the film transformation rate is greater than the potential changes wich allows a film rearrangement for each potential. The electrochemical ageing in the anodic potential inside the passive region shows that thé reduction process of the passivating film grown in potentiostatic or potentiodynamic conditions is affected by the Niobium content

ASSUNTO(S)

niobio - metalurgia superficies (tecnologia) aço inoxidavel

ACESSO AO ARTIGO

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