Smart Functionalization of Ceramic-coated AZ31 Magnesium Alloy

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Abstract

Providing materials with smart functionalities such as self-healing properties is primarily a domain for organic materials, although their applicability is restricted to mild environments and loads due to poor thermal and mechanical properties. This work seeks to achieve the active functionalities obtained in organic materials but in ceramics, which are much more heat resistant and robust. Ceramic coatings were produced by Plasma Electrolytic Oxidation (PEO), which is an environmentally friendly technique that offers an alternative to potentially carcinogenic treatments used widely in the automotive and aircraft industries to protect light alloys against corrosion. The active functionalisation was achieved by incorporating corrosion inhibitors encapsulated into halloysite nanotubes (HNTs) into the PEO coatings. This allowed a controlled release of active agents when detecting environmental pH changes associated with the corrosion initiation of the metal substrate. Three corrosion inhibitors – vanadate, molybdate salts and 8–hydroxyquinoline (8–HQ) – were assessed within the PEO–HNT system and demonstrated considerable improvements in the corrosion resistance by decreasing the kinetics of both anodic and cathodic reactions. For immersion times up to 72 h, the vanadate offered a consistently higher corrosion resistance which was followed by molybdate, whereas the positive effect of 8–HQ was time-limited. The improvement in corrosion resistance was associated with the combined enhancement of the barrier and active protection properties of ceramic coatings. All coatings containing corrosion inhibitors were capable of providing self-healing to small scratches whereas only vanadate could partially restore more severe damages.

Bibliographical metadata

Original languageEnglish
Pages (from-to)30833-30846
Number of pages14
JournalACS applied materials & interfaces
Volume12
Issue number27
Early online date10 Jun 2020
DOIs
Publication statusPublished - 10 Jun 2020

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