Perfect Combination of LBL with Sol-Gel Film to Enhance the Anticorrosion Performance on Al Alloy under Simulated and Accelerated Corrosive Environment.

Xia Zhao,Xiaolin Sun,Shuai Yuan,Binbin Zhang,Zuquan Jin,Shibo Chen,Jizhou Duan,Nazhen Liu,Shuan Liu

doi:10.3390/ma13010111

Abstract

Given their outstanding versatile properties, multilayered anticorrosion coatings have drawn great interest from researchers in the academic and engineering fields. However, the application of multilayered coatings is restricted by some limitations such as low interlayer compatibilities, the harsh preparation process, etc. This work introduced a composite film fabricated on a 2A12 aluminum alloy surface, including an anodic oxide film, a sol–gel film, and a layer-by-layer (LBL) self-assembling film from bottom to top. The microstructure and elemental characterization indicated that the finish of the coating with the LBL film resulted in a closely connected multilayered coating with a smoother surface. The anticorrosion performance was systematically evaluated in the simulated corrosive medium and neutral salt spray environment. The integrated coating with the LBL film presented an excellent anticorrosion ability with system impedance over 108 Ω·cm2 and a self-corrosion current density two orders of magnitude lower than that of the other coatings. After the acceleration test in a salt spray environment, the multilayered coatings could still show a good protective performance with almost no cracks and no penetration of chloride ions. It is believed that the as-constructed multilayered coating with high corrosive properties and a fine surface state will have promising applications in the field of anticorrosion engineering.

Highlights

These results further proved that the LBL film could combine perfectly with the sol–gel film and obtain a protective film with excellent resistance to external erosion
A multilayered coating was successfully fabricated on a 2A12 aluminum alloy surface combining anodization, sol–gel, and LBL strategies
The anodic oxide film and sol–gel film can improve the anticorrosive abilities of the Al alloy, with the charge transfer resistant increased by one or two orders of magnitude compared to the blank Al alloy

Summary

Introduction

Aluminum and its alloys are widely used in the fields of shipbuilding, oceanography engineering, aerospace, and machine manufacturing because of its low density, low thermal expansion coefficient, high strength, and strain performance [1,2], which have drawn much attention from both researchers and engineers as promising materials for electrical appliances and the machinery industry [3,4,5,6,7,8].Under certain circumstances, Al alloys possess some anticorrosion resistance because of the naturallyMaterials 2020, 13, 111; doi:10.3390/ma13010111 www.mdpi.com/journal/materialsMaterials 2020, 13, 111 formed oxidized thinner film [9,10]. Al alloys possess some anticorrosion resistance because of the naturally. The natural thin and inhomogeneous oxide film dissolves substantially when exposed to corrosive environments containing aggressive chloride ions, resulting in localized corrosion, mechanical failure, considerable financial cost, and even catastrophic accidents [11,12]. In order to improve the corrosion resistance and stability of the Al alloys, more protective technologies need to be explored to extend their service life in some special environment, such as marine, industry, etc. Artificial fabricated films upon Al alloy substrates are commonly used to improve the protective ability, including anodic oxidation [15,16], laser cladding [17], the sol–gel method [18], self-assembly technology [19,20], anticorrosion coatings [21] etc

Methods

Results

Conclusion