Wierzbicka Ewa, Vaghefinazari Bahram, Mohedano Marta, Visser Peter, Posner Ralf, Blawert Carsten, Zheludkevich Mikhail, Lamaka Sviatlana, Matykina Endzhe, Arrabal Raúl
Departamento de Ingeniería Química y de Materiales, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain.
Department of Functional Materials and Hydrogen Technology, Faculty of Advanced Technologies and Chemistry, Military University of Technology, Kaliskiego Street 2, 00-908 Warsaw, Poland.
Materials (Basel). 2022 Nov 29;15(23):8515. doi: 10.3390/ma15238515.
Although hexavalent chromium-based protection systems are effective and their long-term performance is well understood, they can no longer be used due to their proven Cr(VI) toxicity and carcinogenic effect. The search for alternative protection technologies for Mg alloys has been going on for at least a couple of decades. However, surface treatment systems with equivalent efficacies to that of Cr(VI)-based ones have only begun to emerge much more recently. It is still proving challenging to find sufficiently protective replacements for Cr(VI) that do not give rise to safety concerns related to corrosion, especially in terms of fulfilling the requirements of the transportation industry. Additionally, in overcoming these obstacles, the advantages of newly introduced technologies have to include not only health safety but also need to be balanced against their added cost, as well as being environmentally friendly and simple to implement and maintain. Anodizing, especially when carried out above the breakdown potential (technology known as Plasma Electrolytic Oxidation (PEO)) is an electrochemical oxidation process which has been recognized as one of the most effective methods to significantly improve the corrosion resistance of Mg and its alloys by forming a protective ceramic-like layer on their surface that isolates the base material from aggressive environmental agents. Part II of this review summarizes developments in and future outlooks for Mg anodizing, including traditional chromium-based processes and newly developed chromium-free alternatives, such as PEO technology and the use of organic electrolytes. This work provides an overview of processing parameters such as electrolyte composition and additives, voltage/current regimes, and post-treatment sealing strategies that influence the corrosion performance of the coatings. This large variability of the fabrication conditions makes it possible to obtain Cr-free products that meet the industrial requirements for performance, as expected from traditional Cr-based technologies.
尽管基于六价铬的防护体系是有效的，且其长期性能也已得到充分了解，但由于已证实的六价铬毒性和致癌作用，它们已不再被使用。对镁合金替代防护技术的探索至少已经进行了几十年。然而，与基于六价铬的体系具有同等功效的表面处理体系直到最近才开始出现。要找到足以替代六价铬且不会引发与腐蚀相关安全问题的防护材料仍然具有挑战性，尤其是在满足交通运输行业要求方面。此外，在克服这些障碍时，新引入技术的优势不仅要包括健康安全，还需要在增加的成本、环境友好性以及易于实施和维护之间取得平衡。阳极氧化，特别是在击穿电位以上进行时（该技术称为等离子体电解氧化（PEO）），是一种电化学氧化过程，已被公认为是通过在镁及其合金表面形成类似陶瓷的保护层，将基材与侵蚀性环境介质隔离开来，从而显著提高其耐腐蚀性的最有效方法之一。本综述的第二部分总结了镁阳极氧化的发展情况和未来展望，包括传统的基于铬的工艺以及新开发的无铬替代品，如PEO技术和有机电解质的使用。这项工作概述了影响涂层耐腐蚀性能的工艺参数，如电解质成分和添加剂、电压/电流范围以及后处理密封策略。制造条件的这种巨大差异使得能够获得满足工业性能要求的无铬产品，正如传统基于铬的技术所期望的那样。
