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Anodic oxidation of a Ni-Cr alloy in a molten electrolyte - effect of temperature and melt composition

机译：Ni-Cr合金在熔融电解质中的阳极氧化-温度和熔体成分的影响

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摘要

A study of the anodic oxidation of a Ni-10 wt.% Cr alloy in molten NaOH and NaOH-Li2CO3 is presented, emphasising the role of temperature and carbonate addition in the mechanism of growth, the composition and the structure of the surface oxide films. The potential ranges of passivation, passivity and transpassivity have been determined by voltammetry. Impedance measurements were performed in the passive potential region to investigate the conductivity mechanism of the oxide films as depending on the temperature and melt composition. The surface composition of the oxides has been estimated by X-ray photoelectron spectroscopy (XPS) and their in-depth composition by Auger electron spectroscopy (AES). As a result, the main passivation product on the Ni surface was found to be a non-stoichiometric and/or partly hydrated NiO. A bilayer structure of the surface film is hypothesised, the inner barrier layer being tentatively identified with a Cr-substituted NiO and the outer deposited layer as a mixture of non-stoichiometric NiO and a Ni-Na or Ni-Li oxides. The transport of nickel cation vacancies through the barrier sublayer was assumed to be the rate-limiting step of the overall process in the passive region. The increase in thickness of the surface film with temperature is interpreted as due to the increase of the rate of cation vacancy transport through the barrier layer, leading to an increased secondary-film precipitation rate. © 2005 Elsevier B.V. All rights reserved.
机译：提出了对Ni-10 wt％Cr合金在熔融NaOH和NaOH-Li2CO3中进行阳极氧化的研究，强调温度和碳酸盐的添加在表面氧化膜的生长机理，组成和结构中的作用。 。钝化，钝化和透射钝化的潜在范围已通过伏安法确定。在无源电势区域中进行阻抗测量，以研究取决于温度和熔体成分的氧化膜的电导率机理。氧化物的表面组成已通过X射线光电子能谱（XPS）进行了估算，其深度组成已通过俄歇电子能谱（AES）进行了估算。结果，发现Ni表面上的主要钝化产物是非化学计量的和/或部分水合的NiO。假设表面膜的双层结构，内阻挡层用Cr取代的NiO暂定，外沉积层用非化学计量的NiO和Ni-Na或Ni-Li氧化物的混合物标识。镍离子空位通过势垒子层的传输被认为是整个钝化区域过程的限速步骤。表面膜的厚度随温度的增加被解释为是由于阳离子空位传输通过阻挡层的速率增加，从而导致次级膜沉淀速率增加。 ＆复制; 2005 Elsevier B.V.保留所有权利。

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