镁合金原位生长水滑石研究进展

Research Progress of In-situ Growth of Layered Double Hydroxides on Magnesium Alloys

镁合金是常见轻质金属结构材料,但易腐蚀的特性限制了其在工业中的广泛应用。水滑石具有超强的吸附能力和阴离子可交换性等特点,可为镁合金提供有效防护。文章综述了镁合金原位生长水滑石的研究进展,主要包括成膜工艺、成膜机理、防腐蚀机理及在镁合金防腐涂层中的应用。目前常用的制备方法包括原位直接生长法、两步法、阴离子置换法和电沉积法。原位生长法制备较为简单,但会出现较多的副产物;而两步法和阴离子置换法可以通过控制反应条件和调节溶液成分来实现水滑石的原位生长,能够得到较好的涂层质量和性能;电沉积法更为高效快速,但涂层结合力有待提高。现有的水滑石成膜机理大体可以分为4种成膜机理,而水滑石往往会在第二相附近和缺陷处优先形核。水滑石涂层防腐机理可以概括为涂层屏蔽、离子吸附和涂层自愈合。最后对水滑石未来的发展进行了展望。

Magnesium alloy is a common lightweight metal structural material,but its corrosion-prone property limit its wide application in industry.Hydrotalcite can provide effective protection for magnesium alloys due to the properties of super adsorption capacity and anion exchangeability.In this paper,the research progress of in-situ growth of hydrotalcite in magnesium alloys was reviewed,including film formation process and mechanism,corrosion protection mechanism and application in anticorrosive coating for magnesium alloy,and the future development was prospected.At present,the commonly used preparation methods include in-situ growth,two-step method,anion exchange method and electrodeposition.The in-situ growth method is simple,but more by-products will be produced.The in-situ growth of hydrotalcite can be achieved by two-step method and anion replacement method by controlling reaction conditions and adjusting solution composition,and better coating quality and performance can be obtained.Electrodeposition is efficient and rapid,but the adhesion of the prepared coating needs to be improved.There are four film formation mechanisms for hydrotalcite film formation,and hydrotalcite tends to nucleate preferentially near the second phase and at defects.And the corrosion protection mechanism of hydrotalcite coating could be summarized as shielding,adsorption of ion and self-healing.