Improved corrosion resistance of AZ31B Mg alloy by eco-friendly flash-PEO coatings
The aim of this work was the preparation of an environmentally friendly protective coating on the AZ31B alloy using Flash plasma electrolytic oxidation (F-PEO) process. It was developed with different electrolyte compositions, that determine the morphology and properties of the coatings, this being...
| Autores: | , , , , , |
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| Tipo de documento: | artigo |
| Estado: | Versão publicada |
| Data de publicação: | 2024 |
| País: | España |
| Recursos: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositório: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/380537 |
| Acesso em linha: | http://hdl.handle.net/10261/380537 https://www.scopus.com/inward/record.uri?eid=2-s2.0-85185781465&doi=10.1016%2fj.apsadv.2024.100587&partnerID=40&md5=dead2a6bbfaa8bdaf19606137d228d6d |
| Access Level: | Acceso aberto |
| Palavra-chave: | Carbonate Corrosion resistance Environmentally friendly electrolyte Flash-PEO Low-energy consumption Mg alloy |
| Resumo: | The aim of this work was the preparation of an environmentally friendly protective coating on the AZ31B alloy using Flash plasma electrolytic oxidation (F-PEO) process. It was developed with different electrolyte compositions, that determine the morphology and properties of the coatings, this being crucial to understand the anti-corrosion properties. The incorporation of carbonate ions to the electrolyte proved to enhance the electrical response of the F-PEO process, resulting in a more efficient process with an energy reduced consumption of 1.1 kW h m−2μm−1. Surface and cross-sectional morphology analysis of the coatings revealed the presence of isolated pores structure with small pore size (less than 1 µm) that delays the infiltration of aggressive ions towards the substrate. The characterisation by XRD, EDX and Raman spectroscopy showed the presence of amorphous carbonate and phosphate phases in the FPEO-CO layer, that provide a self-restauration effect through a dissolution/reprecipitation mechanism. The lowest value of the corrosion current density was obtained for FPEO-CO coating, 4.60 × 10−7 A·cm−2, together with the highest impedance modulus (f<0.1 Hz), ⁓104 Ω·cm2, two orders of magnitude higher than the AZ31B Mg alloy. Furthermore, the corrosion protection properties of FPEO-CO coating were also analysed through an immersion test in 3.5 wt.% NaCl, confirming the excellent response of the coating for long times up to 336 h (2 weeks). The synergy between a more compact coating and the self-repairing ability of carbonate amorphous species plays a critical role in improving the corrosion resistance properties of the AZ31B Mg alloy, offering an eco-friendly alternative to chromate conversion coatings. © 2024 The Author(s) |
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