Corrosion And Protection Of Magnesium Alloys

Magnesium (Mg) alloys are receiving increasing attention due to their abundance, light weight, castability, formability, mechanical properties and corrosion performance. By selecting the appropriate combination of materials, coatings and surface modifications, their corrosion resistance can be greatly enhanced. Corrosion prevention of magnesium alloys is a comprehensive guide to the effective prevention of corrosion in these important light metals. Part one discusses alloying, inhibition and prevention strategies for magnesium alloys as well as corrosion and prevention principles. Part two reviews surface treatment and conversion. Beginning with an overview of surface cleaning and pre-conditioning, the book goes on to discuss the use of surface processing and alloying, laser treatments, chemical conversion and electrochemical anodization to improve the corrosion resistance of magnesium alloys. Coatings are then the focus of part three, including varied plating techniques, cold spray coatings, gel and electroless electrophoresis coatings. Finally, the book concludes in part four with a selection of case studies investigating the application of preventative techniques for both automotive and medical applications. With its distinguished editor and international team of expert contributors, Corrosion prevention of magnesium alloys is a key reference tool for all those working with magnesium and its alloys, including scientists, engineers, metallurgists, aerospace and automotive professionals, and academics interested in this field. Chapters provide an overview of surface cleaning and pre-conditioning Examines processes to improve the corrosion resistance of magnesium alloys, including laser treatments and chemical conversion and electrochemical anodization Discusses cold spray, sol-gel and electrophoretic coatings

The use of magnesium alloys is increasing in a range of applications, and their popularity is growing wherever lightweight materials are needed. This book provides a comprehensive account of the corrosion of magnesium alloys. It covers not only the corrosion performances and mechanisms of Mg alloys in conventional environments, such as sodium chloride solutions, but also looks at their corrosion behaviours in special media, like engine coolants and simulated body fluids. Part one covers fundamentals such as the corrosion electrochemistry, activity and passivity of magnesium and its alloys. Part two then considers the metallurgical effect in relation to the corrosion of magnesium alloys, including the role of micro-structure and earth-rare elements, the corrosion behaviour of magnesium-based bulk metallic glasses, and the corrosion of innovative magnesium alloys. Part three goes on to describe environmental influences on the corrosion of magnesium alloys, such as atmospheric corrosion, stress corrosion cracking, creep and fatigue behaviour, and galvanic corrosion. Finally, part four is concerned with various means of protecting magnesium alloys against corrosion through the use of aluminium electrodeposition, conversion and electrophoretic coatings, and anodisation. With its distinguished editor and team of contributors, this book is an invaluable resource for metallurgists, engineers and designers working with magnesium and its alloys, as well as professionals in the aerospace and automotive industries.

Magnesium (Mg) alloys, possessing good thermal and electrical conductivity, low density, recyclability, high specific strength, and excellent damping capacity, are regarded as one of the most promising light metallic materials. Mg alloys are also known as the “inexhaustible green light engineering material” compared with steel, aluminum, copper, and engineering plastics, providing some important applications in communications, automotive, defense, aerospace, and biomedical industries. However, the low electrode potential causes poor corrosion resistance in the environment of moist air, sulfur, and marine atmosphere. And thus, the corrosion and protection technology of Mg and its alloys is listed as an important research topic in this field. In this Research Topic, the latest research papers on corrosion and protection of Mg and its alloys are collected to provide a platform for researchers and readers to understand the recent developments in this field. Good use of this platform could improve the international research level in corrosion and protection of Mg and its alloys and promote the “green, safe, life-extending and smart” anti-corrosion technology and expand the application range of Mg and its alloys. High-quality Original Research and Review articles in this field are all welcome for submission to this Research Topic. Research interests include but are not limited to the following areas: • Corrosion behaviors and mechanisms • Surface treatment technology • Biodegradable medical applications • High-temperature oxidation • Inhibitors for Mg and its alloys • New monitoring, evaluation, simulation, and prediction methods

Magnesium (Mg) alloys have low corrosion resistance and exhibit unusual corrosion behavior in aqueous environments. Because of this unique corrosion performance, some special corrosion prevention techniques have to be employed for Mg alloys in their applications. This chapter briefly summarizes the corrosion characteristics of Mg alloys, and also presents a strategy and methodologies to mitigate the corrosion damage of Mg alloys in applications.

This memorandum deals with the corrosion protection of magnesium and magnesium alloys. The corrosion resistance of these alloys in many natural environments, while not as good as that of copper, nickel, stainless steel, and aluminum, is in the same range as that of the iron and plain carbon steels. Some type of additional corrosion protection is often necessary and, as with steel, the protective measures usually involve some type of coating system and/or surface treatments. Also, magnesium can suffer accelerated attack when coupled, in the presence of a conductive electrolyte, to most metals below it in the galvanic series. This galvanic effect complicates the problem of corrosion protection. A number of coating systems have been proposed and used satisfactorily. Depending upon the application, these coating systems include the use of conversion coatings, organic coatings, metallic coatings, and others. In addition, special designs can be employed to improve the over-all corrosion resistance of the systems. This memorandum describes many of the coating systems and design methods which are used to reduce corrosive attack on both galvanically coupled and uncoupled magnesium assembliesd (Author).

The escalation of ongoing research on the topic of conversion coatings for magnesium alloys confirms that the search continues for appropriate replacements to toxic chromate-based coatings. This chapter reviews the performance of the range of typical conversion coating technologies presently available. As a means to rationalise coating performance and characteristics more generally, thermodynamic analysis has been used to compare coating processes and coating pretreatment, the latter of which appears to be at least as significant as the choice of coating technology itself.

Magnesium alloys with their unique physical and chemical properties are important candidates for many modern engineering applications. Their density, being the lowest of all structural metals, makes them the primary choice in global attempts aimed at reducing the weight of transportation vehicles. However, magnesium also creates challenges at certain stages of raw alloy melting, fabrication of net-shape components and their service. The first one is caused by very high affinity of magnesium to oxygen, which requires protective atmospheres increasing manufacturing cost and heavily contributing to greenhouse gas emissions. The second challenge relates to very high corrosivity of liquid magnesium towards materials it contacts. This imposes restrictions on the selection of materials used to contain, transfer or process molten magnesium during manufacturing operations. A mixture of unique benefits and serious challenges of magnesium alloys in solid and liquid states described here makes the book very useful for a broad audience of scientists and engineers from academia and industry.

Plating on Mg alloys has proved difficult due to their high susceptibility to the degradation reactions such as galvanic corrosion in the plating processes. In this chapter, surface conditioning, activation, electroless- or electroplating methods are discussed from viewpoints of corrosion engineering. Degradation reactions of the Mg substrate in each plating stage are considered to figure out how to suppress degradation of substrate and to achieve uniform deposition of a plating layer. Building up an interface between the substrate and the plating layer is also an important subject to establish enough adhesion strength of the plating layer and low defect density to prohibit corrosion progress of the substrate. Al coating plating on Mg alloys electrodeposited from an ionic liquid bath is also introduced to provide coatings with less-galvanic coupling property with a less-noble Mg substrate.

This book covers fundamentals and recent advancements on conversion coatings for magnesium and its alloys. The contents are presented in two sections, respectively dealing with chemical and electrochemical conversion coatings. The chemical conversion coating section is further subdivided into inorganic conversion coatings, organic conversion coatings and advanced approaches/coatings. The section on electrochemical conversion coatings spans from fundamentals to state-of-the-art progress on electrochemical anodization and plasma electrolytic oxidation of magnesium and its alloys.

Sol-gel coatings have been widely used to improve corrosion resistance of Mg alloys. This chapter summarizes the history of development of sol-gel coatings, the mechanism and research results of sol-gel coatings improving the corrosion resistance of Mg alloys and some relevant applications. In addition, the prospects of the future development of sol-gel coatings on Mg alloy are presented.