锌电积用铅基合金阳极氧化层“结构-性能”优化调控基础研究

The core content of this project is oxide layer structure of Pb-base alloy anode, including two main points: first, the relationship between structure and performance; second, the formation mechanism of oxide layer. Anodic oxidation layer, the transition layer between lead alloy substrate and acid solution, is directly contact with acid solution is the major carrier of the oxygen evolution. The anodic oxidation layer structure directly affects oxygen evolution potential and work-durability of Pb-based alloy anodes during zinc electroextraction. The Pb-Ag, Pb-Ag-Ca anode that widely used in industry and Pb-Co, Pb-Ag-Sn-Co anode with a good application prospect will be selected as the research object in this project. The relationship between structure and performance will be evaluated (semi-)quantitatively by sensitive electrochemical analysis test and the characterization methods of structure and phase during 15 d of galvanostatic polarization. The formation mechanism will be investigated in turn according to the special oxidation layer structure. The selectively driving force of Ag and Co towards oxidation layer will be explored. And the correlated theoretical model will be established. On this basis, the promising alternative element of Ag and Co will be developed by introducing base and easy alloying metal to induce the production of high quality anodic oxide layer such as Pb-Ag and Pb-Co.

本项目研究核心是铅基合金阳极氧化层结构。包括两个重点：（1）氧化层结构与阳极宏观使用性能的关系；（2）氧化层结构形成的受控因素。阳极氧化层直接与酸性溶液接触，是铅合金基体与酸性溶液之间的过渡层，也是析氧反应的主要载体。阳极氧化层的结构直接影响析氧电位和阳极使用寿命。本项目选取工业中大规模使用的Pb-Ag和Pb-Ag-Ca阳极以及有较好应用前景的Pb-Co和Pb-Ag-Sn-Co阳极为研究对象。在15天连续极化过程中，运用灵敏的电化学分析测试结合微观形貌、物相等表征方法“定量-半定量”评估阳极氧化层“结构-性能”的关系。针对特殊的氧化层结构反推其形成机理，研究铅合金中Ag、Co对阳极氧化层结构物相的深层次选择性驱动力，并建立相关理论模型。在此基础上，探索Ag和Co可能的替代性元素，通过引入贱金属且易于合金化的金属“诱导”铅基合金产生“类Pb-Ag系”或“类Pb-Co系”优质阳极氧化层结构。

工业中湿法炼锌电沉积工序主要采用铅基合金作为阳极，其析氧过电位高达八百多毫伏，是无用电耗的主要根源。阳极析氧过电位与阳极氧化层的微观结构、物相、孔隙度、导电性、附着力、电催化活性、形成稳定过程密切相关。本项目围绕铅基合金阳极氧化层“结构-性能”优化调控关系，主要研究了铅银合金、铅银钙合金在氯离子、锰离子体系阳极氧化层形成稳规律。通过析氧过电位，表观交换电流密度，电荷传递电阻，表面粗糙度，氧化层微观结构与物相等参数“定量-半定量”表征了铅合金氧化层的形成稳定特点。并开发了铅合金预镀膜处理工艺，对铅银合金、铅银钙合金预镀膜处理，并考察了对阳极氧化层形成稳定影响。结果表明随着极化时间的延长，析氧过电位逐渐降低，表观交换电流密度逐渐升高，氧化层呈现了一个形成稳定过程。在极化过程中阳极氧化层的形成主要受三方面因素的支配：铅基合金类型，是否预镀膜处理，电积溶液组分。预镀膜处理可以改变氧化层的物相结构，并提高电极的催化活性及耐腐蚀性，氯离子存在会抑制β-PbO2的形成。在此基础上，开发出了适用于氯离子体系的不锈钢基二氧化铅涂层阳极和适用于锰离子体系的镀膜铅银钙合金阳极，获得了良好的性能，具有良好的应用前景。