Dual Role of Lithium on the Structure and Self-Healing Ability of PMMA-Silica Coatings on AA7075 Alloy

Author(s)

Trentin, Andressa ^[1] ; Harb, Samarah V. ^[1] ; Uvida, Mayara C. ^[1] ; Pulcinelli, Sandra H. ^[1] ; Santilli, Celso V. ^[1] ; Marcoen, Kristof ^[2] ; Pletincx, Sven ^[2] ; Terryn, Herman ^[2] ; Hauffman, Tom ^[2] ; Hammer, Peter ^[1]

Affiliation

^[1] Sao Paulo State Univ UNESP, Inst Chem, BR-14800060 Araraquara, SP - Brazil

^[2] Vrije Univ Brussel, Dept Mat & Chem, Res Grp Electrochem & Surface Engn, Pl Laan 2, B-1050 Brussels - Belgium

• Document type: Journal article
• Source: ACS APPLIED MATERIALS & INTERFACES; v. 11, n. 43, p. 40629-40641, OCT 30 2019.
• Web of Science Citations: 0

Abstract

In this work, structural and active corrosion inhibition effects induced by lithium ion addition in organic inorganic coatings based on poly(methyl methacrylate) (PMMA)-silica sol gel coatings have been investigated. The addition of increasing amounts of lithium carbonate (0, 500, 1000, and 2000 ppm), yielded homogeneous hybrid coatings with increased connectivity of nanometric silica cross-link nodes, covalently linked to the PMMA matrix, and improved adhesion to the aluminum substrate (AA7075). Electrochemical impedance spectroscopy (EIS), performed in 3.5% NaCl aqueous solution, showed that the improved structural properties of coatings with higher lithium loadings result in an increased corrosion resistance, with an impedance modulus up to 50 G Omega cm(2), and revealed that the lithium induced self-healing ability significantly improves their durability. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) suggest that the regeneration process occurs by means of lithium ions leaching from the adjacent coating toward the corrosion spot, which is restored by a protective layer of precipitated Li rich aluminum hydroxide species. An analogue mechanism has been proposed for artificially scratched coatings presenting an increase of the impedance modulus after salt spray test compared to the lithium free coating. These results evidence the active role of lithium ions in improving the passive barrier of the PMMA-silica coating and in providing through the self-restoring ability a significantly extended service life of AA7075 alloy exposed to saline environment. (AU)

• FAPESP's process: 15/11907-2 - Structure and electrochemical properties of PMMA-silica hybrid coatings modified with cerium and lithium ions.
• Grantee: Andressa Trentin
• Support type: Scholarships in Brazil - Doctorate
• FAPESP's process: 17/14061-2 - Influence of Ce(iii) and Ce(IV) ions on the structural and electrochemical characteristics of PMMA-silica hybrid coatings
• Grantee: Andressa Trentin
• Support type: Scholarships abroad - Research Internship - Doctorate
• FAPESP's process: 15/09342-7 - Development of multifunctional PMMA- (TiO2, ZrO2 and CeO2)hybrids
• Grantee: Samarah Vargas Harb
• Support type: Scholarships in Brazil - Doctorate