Design of Corrosion Protective and Antistatic Hybrid Sol-Gel Coatings on 6XXX AlMgSi Alloys for Aerospace Application

Abstract

An inorganic–organic coating based on glycidyl-functionalized silica and zirconia was synthesized by sol-gel technology to protect three types of AlMgSi (6XXX series) alloys against corrosion in aerospace applications. Different parameters such as the solid content, the organic/inorganic ratio of the sols and the deposition conditions were studied with the aim to achieve a tradeoff between the corrosion protection, antistatic performance and low vacuum-induced outgassing. Those parameters directly influence the thickness and the density of the coatings, and therefore the barrier effect against corrosion and the contact electrical resistance, which are affected in opposite ways. To obtain a low contact electrical resistance, silver nanowires (NW) with a high aspect ratio were loaded in the sol-gel matrix with the aim to create a conductive path through the hybrid coating with a low concentration of NWs. The coatings were adapted for AA6063, AA6061 and AA6082, and they all showed an outstanding anti-corrosion performance in different artificial weathering tests, whereas electrochemical impedance spectroscopy permitted the identification of the most critical parameters affecting water uptake. An antistatic performance was demonstrated by the low contact electrical resistance of the coated AA6061 and AA6063 alloys, although the incorporation of NWs showed a detrimental effect on the corrosion protection compared with the unloaded coating.

Superhydrophobic and oleophobic microtextured aluminum surface with long durability under corrosive environment

“…This ⁓ 1.6 μm thick coating was composed of methacrylate, silica and zirconia with polyfluoroalkyl moieties covalently linked to the matrix through Si-C bonds. It has been demonstrated in previous works of authors 28,29 , that the application of sol-gel coatings on aluminum surfaces by dip-coating does not follow a conformational growth, since it contributes to the surface levelling as schematically represented in Fig. 2.…”

Conductive, Anti-Corrosion, Self-Healing Smart Coating Technology Incorporating Graphene-Based Nanocomposite Matrix

“…Bringing conductive or low electrical resistance properties to sol-gel anticorrosive and UV-curable coatings has been attempted by dispersing conductive nanofillers within the solgel matrices. Unfortunately, it was shown that this incorporation cause a negative effect on the achieved anticorrosive properties since the fillers compromise the mechanical and barrier properties of the coatings creating local defects and provide an electrical path for corrosion to take place (Zhang Q. et al, 2018;Agustín-Sáenz et al, 2020;Tian et al, 2021).…”

Effect of Ammonia Addition on the Growth of an AlO(OH) Film during Steam Coating Process

“…Various surface treatment techniques have been developed and implemented to improve the corrosion resistance of alloys. Specifically, surface treatment techniques, such as anodic oxidation [16][17][18][19], electroplating [20,21], conversion treatment [22], and sol gel method [23,24] have been industrially used for different kinds of Al alloys. However, in these surface treatment processes, the waste liquid generated needs to be treated before disposal, and there is a risk of environmental pollution caused by heavy metals [25].…”