Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: Part II—PEO and Anodizing
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 le...
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| Format: | Article |
| Language: | English |
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MDPI AG
2022-11-01
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| Series: | Materials |
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| Online Access: | https://www.mdpi.com/1996-1944/15/23/8515 |
| _version_ | 1797462760983887872 |
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| author | Ewa Wierzbicka Bahram Vaghefinazari Marta Mohedano Peter Visser Ralf Posner Carsten Blawert Mikhail Zheludkevich Sviatlana Lamaka Endzhe Matykina Raúl Arrabal |
| author_facet | Ewa Wierzbicka Bahram Vaghefinazari Marta Mohedano Peter Visser Ralf Posner Carsten Blawert Mikhail Zheludkevich Sviatlana Lamaka Endzhe Matykina Raúl Arrabal |
| author_sort | Ewa Wierzbicka |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-03-09T17:41:14Z |
| format | Article |
| id | doaj.art-03887f03dbc0407ca52adbe778d6ecd9 |
| institution | Directory Open Access Journal |
| issn | 1996-1944 |
| language | English |
| last_indexed | 2024-03-09T17:41:14Z |
| publishDate | 2022-11-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Materials |
| spelling | doaj.art-03887f03dbc0407ca52adbe778d6ecd92023-11-24T11:29:32ZengMDPI AGMaterials1996-19442022-11-011523851510.3390/ma15238515Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: Part II—PEO and AnodizingEwa Wierzbicka0Bahram Vaghefinazari1Marta Mohedano2Peter Visser3Ralf Posner4Carsten Blawert5Mikhail Zheludkevich6Sviatlana Lamaka7Endzhe Matykina8Raúl Arrabal9Departamento de Ingeniería Química y de Materiales, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, SpainInstitute of Surface Science, Helmholtz-Zentrum Hereon, 21502 Geesthacht, GermanyDepartamento de Ingeniería Química y de Materiales, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, SpainAkzoNobel, 2171 EN Sassenheim, The NetherlandsHenkel AG & Co. KGaA, 40191 Düsseldorf, GermanyInstitute of Surface Science, Helmholtz-Zentrum Hereon, 21502 Geesthacht, GermanyInstitute of Surface Science, Helmholtz-Zentrum Hereon, 21502 Geesthacht, GermanyInstitute of Surface Science, Helmholtz-Zentrum Hereon, 21502 Geesthacht, GermanyDepartamento de Ingeniería Química y de Materiales, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, SpainDepartamento de Ingeniería Química y de Materiales, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, SpainAlthough 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.https://www.mdpi.com/1996-1944/15/23/8515magnesiumcoatingmicro-arc oxidation (MAO)Cr(VI)-based coatings |
| spellingShingle | Ewa Wierzbicka Bahram Vaghefinazari Marta Mohedano Peter Visser Ralf Posner Carsten Blawert Mikhail Zheludkevich Sviatlana Lamaka Endzhe Matykina Raúl Arrabal Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: Part II—PEO and Anodizing Materials magnesium coating micro-arc oxidation (MAO) Cr(VI)-based coatings |
| title | Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: Part II—PEO and Anodizing |
| title_full | Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: Part II—PEO and Anodizing |
| title_fullStr | Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: Part II—PEO and Anodizing |
| title_full_unstemmed | Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: Part II—PEO and Anodizing |
| title_short | Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: Part II—PEO and Anodizing |
| title_sort | chromate free corrosion protection strategies for magnesium alloys a review part ii peo and anodizing |
| topic | magnesium coating micro-arc oxidation (MAO) Cr(VI)-based coatings |
| url | https://www.mdpi.com/1996-1944/15/23/8515 |
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