Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: Part III—Corrosion Inhibitors and Combining Them with Other Protection Strategies

Vaghefinazari, Bahram; Wierzbicka, Ewa; Visser, Peter; Posner, R.; Arrabal, R.; Matykina, E.; Mohedano, M.; Blawert, Carsten; Zheludkevich, Mikhail L.; Lamaka, Sviatlana V.

doi:10.3390/ma15238489

Cited by 14 publications

(8 citation statements)

References 265 publications

(411 reference statements)

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“…PART II of the review [ 5 ] focuses on Plasma Electrolytic Oxidation (PEO) coating as one of the highly developed methods to protect magnesium surface in the recent years. PART III [ 6 ] reviews corrosion inhibitors for magnesium and approaches to incorporate them into coating systems. An overview of the review trilogy is illustrated in the graphical abstract of all three review parts.…”

Section: Forewordmentioning

confidence: 99%

Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: PART I—Pre-Treatment and Conversion Coating

et al. 2022

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Corrosion protection systems based on hexavalent chromium are traditionally perceived to be a panacea for many engineering metals including magnesium alloys. However, bans and strict application regulations attributed to environmental concerns and the carcinogenic nature of hexavalent chromium have driven a considerable amount of effort into developing safer and more environmentally friendly alternative techniques that provide the desired corrosion protection performance for magnesium and its alloys. Part I of this review series considers the various pre-treatment methods as the earliest step involved in the preparation of Mg surfaces for the purpose of further anti-corrosion treatments. The decisive effect of pre-treatment on the corrosion properties of both bare and coated magnesium is discussed. The second section of this review covers the fundamentals and performance of conventional and state-of-the-art conversion coating formulations including phosphate-based, rare-earth-based, vanadate, fluoride-based, and LDH. In addition, the advantages and challenges of each conversion coating formulation are discussed to accommodate the perspectives on their application and future development. Several auspicious corrosion protection performances have been reported as the outcome of extensive ongoing research dedicated to the development of conversion coatings, which can potentially replace hazardous chromium(VI)-based technologies in industries.

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Section: Forewordmentioning

confidence: 99%

Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: PART I—Pre-Treatment and Conversion Coating

et al. 2022

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“…Anodizing is commonly used for Al and Ti alloys, but less so for Mg alloys. Cheaper and technologically easier conversion treatment processes are typically preferred for Mg in engineering applications [ 3 ]. For details on advances in chromate-free conversion coatings for Mg alloys in engineering applications, the reader is referred to of the present review [ 4 ].…”

Section: Forewordmentioning

confidence: 99%

“…It has been proven that PEO pores, as a high capacity reservoir for corrosion inhibitors, can provide long-term, active protection for Mg substrates [ 136 ]. For a deeper analysis of the corrosion inhibition mechanism using organic inhibitors added as a post-treatment, the reader is referred to Part III of this review [ 3 ]. The application of stable compounds such as SiO 2 [ 86 ], TiO 2 [ 285 ], and SiO 2 -ZrO 2 [ 286 ] via sol-gel has also proved to be successful.…”

Section: Post-treatmentmentioning

confidence: 99%

“…Apart from the sealing effect of the LDH layer that improves the barrier properties of the PEO coating, the abilities to exchange the anionic inhibitors between its hydroxide layers and release them “on demand” offer active corrosion protection. More details on the active inhibition properties of LDH are provided in Part III of this review [ 3 ].…”

Section: Post-treatmentmentioning

confidence: 99%

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Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: Part II—PEO and Anodizing

et al. 2022

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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.

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“…The high corrosion inhibition activities of chromate and leadbased [5] inhibitors, such as molybdates [6], organic thioglycolates [7], and phosphonates [8], make them one of the most effective types of commercial corrosion inhibitors available today. Despite its efficacy, the inclusion of highly toxic chromate-and lead-based compounds in the formulation of corrosion inhibitors make it an environmental and health hazard [9]. Due to the increasing presence of these inhibitors in the market, there is a great interest in developing alternative, non-toxic formulations, and techniques that remediate the effects of corrosion.…”

Section: Introductionmentioning

confidence: 99%

Rice Hull Ash Nanosilica: Characterization and Its Potential as Silicate Coating for Carbon Steel

Madlangbayan¹

2023

GEOMATE

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Corrosion of steel structures is one of the main causes of destruction and loss of materials due to the damages it can bring to operating, storage, and structural equipment. Anti-corrosion inhibitors available in the market frequently contain chromium and lead, which are hazardous to human health and the environment. This study focused on the synthesis of nanosilica from the agro-industrial byproduct rice hull ash (RHA) and examined its potential as a corrosion barrier. Steel specimens were prepared in the form of 4mm thick disks cut from 16mm steel bars. RHA nanosilica was synthesized via acid precipitation method and characterized using x-ray diffraction (XRD), dynamic light scattering (DLS), atomic force microscopy (AFM), and Fourier Transform Infrared (FTIR) Spectroscopy. After characterization, 2.5%w/v RHA nanosilica was used to formulate sodium silicate as a coating for the steel specimens. The coated specimens were then subjected to Complex Impedance Spectroscopy (CIS) at 20Hz to 20MHz frequency range. The generated Nyquist plot showed that the specimen coated with sodium silicate with RHA nanosilica has a much larger diameter than red oxide indicating better protection against corrosion. The generated Bode plots confirmed this result as it showed that the specimens coated with sodium silicate with RHA nanosilica had higher impedances than those coated with red oxide, especially in the low-frequency regions.

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Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: Part III—Corrosion Inhibitors and Combining Them with Other Protection Strategies

Cited by 14 publications

References 265 publications

Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: PART I—Pre-Treatment and Conversion Coating

Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: PART I—Pre-Treatment and Conversion Coating

Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: Part II—PEO and Anodizing

Rice Hull Ash Nanosilica: Characterization and Its Potential as Silicate Coating for Carbon Steel

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