The phase stability of cerium species in aqueous systems -: I.: E-pH diagram for the Ce-HClO4-H2O system
The phase stability of cerium species in aqueous systems -: I.: E-pH diagram for the Ce-HClO4-H2O system
复制标题
DOI：
10.1149/1.1516775
复制
发表时间：
2002-12-01
影响因子：
3.9
通讯作者：
Stoffer, JO
中科院分区：
文献类型：
--
作者：
Hayes, SA;Yu, P;Stoffer, JO
铈化合物已被确定为替代六价铬作为铝合金转化涂层以提高耐腐蚀性的主要候选者。铈还有望在油漆系统中用作抑制颜料。可以使用自发或非自发电解过程来沉积铈转化涂层。在这两种情况下，氧化铈保护膜都是通过沉淀机制形成的，该机制非常依赖于电化学势和 pH 值。稠合铈的氧化态和相已被证明是薄膜提供的腐蚀防护性能的一个重要方面。由于溶液化学和操作参数对薄膜性能的强烈影响，因此系统稳定性的基本知识至关重要。为此，我们为 Ce-H2O 系统开发了修订后的 E-pH 图。选择 Ce-H2O-HClO4 系统作为示例系统，其中羟基离子是 Ce 离子唯一重要的络合物质。使用有关铈物质的最新热力学数据构建了稳定性图，这些数据不适用于 Pourbaix 地图集中发布的原始图。之前发布的 Ce-H2O 图与此处展示的图之间存在显着差异。进行降水测试是为了验证新图表中所示的趋势。讨论了更新的 E-pH 图对于理解铈转化涂层形成过程的重要性。 (C) 2002 年电化学协会。
Cerium compounds have been identified as leading candidates to replace hexavalent chrome as conversion coatings on aluminum alloys to improve corrosion resistance. Cerium also shows promise for use as an inhibiting pigment in paint systems. The cerium conversion coatings can be deposited using either spontaneous or nonspontaneous electrolytic processes. In both cases the protective cerium oxide film forms by a precipitation mechanism that is very dependent on electrochemical potential and pH. The oxidation state and phase of the condensed cerium has been shown to be an important aspect of the corrosion protection properties provided by the film. Because of the strong influence of the solution chemistry and operating parameters on film performance, a basic knowledge of the system stability is essential. Toward this end, a revised E-pH diagram was developed for the Ce-H2O system. The Ce-H2O-HClO4 system was chosen as an example system in which hydroxy ions are the only significant complexing species for the Ce ions. A stability diagram was constructed using more recent thermodynamic data on cerium species not available for the original diagram published in Pourbaix's atlas. Significant differences were noted between the previously published Ce-H2O diagram and the one presented here. Precipitation tests were carried out to verify the trends indicated in the new diagram. The importance of the updated E-pH diagram in understanding the formation processes of cerium conversion coatings are discussed. (C) 2002 The Electrochemical Society.