Preparation and evaluation of corrosion behavior of GPTMS–TEOS hybrid coatings containing Zr and Ce on aluminum alloy 6061-T6

Abstract

Environmentally friendly organic-inorganic hybrid coatings with different amount of Ce and Zr content were prepared by a sol-gel method and deposited on aluminum alloy 6061-T6. Attenuated total reflectance-Fourier transform infrared spectroscopy and scanning electron microscopy were used to structural study of the hybrid coatings. Adhesion strength of sol-gel coatings to the substrate was also evaluated using pull-off test. Corrosion behavior of the samples was evaluated by cyclic potentiodynamic and linear polarization tests. The obtained results display that adhesion strength of the coatings was enhanced with an increase in zirconium and cerium content. Corrosion analysis showed a decrease in corrosion current density of coated samples two to four orders of magnitude compared to the bare alloy 6061. Decreasing in corrosion current density and increasing in polarization resistance were observed by an increase in Zr and cerium content. The sol-gel-coated layer doped with 20 g/l cerium nitrate offered excellent protection against corrosion. Unlike the bare alloy 6061, the crack-free samples showed no sensitivity to pitting corrosion. Graphical Abstract The present investigation has been based on preparation of hybrid sol-gel coatings with different amount of zirconium and cerium content using dip coating method. Effect of cerium and zirconium content on thickness, adhesion strength and pitting corrosion behavior of the coatings were investigated. Significant decrease in corrosion current density was observed compared to uncoated substrate. Increase in polarization resistance was observed by an increase in zirconium and cerium content.

Effect of silane on corrosion resistance and aerodynamic performance of 6063 Al alloy inertial air–water separator

“…The main elements of the anodizing/silane coating are Al, O, C and Si, as shown in Figure 4(a). The XPS analysis of the silane film in Figure 4(b) and (c) shows that the surface of the silane-treated anodic oxide coating has surface material consisting mainly of Al–O–Si (532.3 eV) (Pathak and Khanna, 2008), Si–O–Si and Si–OH (102.2 eV) (Chen et al , 2021; Bahrami et al , 2015; Huang et al , 2020) and Al 2 O 3 . Al–O–Si is produced by the condensation reaction between the hydrolyzed silicon hydroxyl group of silanes and the AlOOH produced by the hydrothermal treatment of the anodic oxide coating.…”

Nanostructured Surface Finishing and Coatings: Functional Properties and Applications

“…The inorganic moiety gives to the hybrid material some properties among which, hardness, chemical resistance and adhesion to the substrate, whilst the organic one provides elasticity, toughness and low curing temperatures [ 159 , 162 ]. Curing time and temperature, pH, aging concentration, molar ratio and nature of the precursors are all factors that contribute to the final chemical structure of the silane produced [ 159 , 161 , 163 , 164 ].…”

The effect of the organosilane content on the barrier features of sol-gel anticorrosive coatings applied on carbon steel

“…During the first reaction, hydrolysis, the silane alkoXide bond (SieOR) results in the formation of a silanol (SieOH). Once this reaction has taken place, two silanols can combine deleting a water molecule in the condensation reaction and form an inorganic highly dense silica net-work by means of siloXane bonds (SieOeSi) [1][2][3][4][5].…”

“…However, through time, several researchers have probed the benefits of organic-inorganic hybrid materials which are obtained from the structural incorporation of organic groups, such as epoXy, amine, vinyl, acrylic, etc., via SieC bonds within the sol-gel precursors. This hybrids offer the possibility to combine both properties; on one hand inorganic (hardness, chemical resistance, adhesion to the substrate…) and on the other hand the organic ones (elasticity, toughness, low curing tem-peratures…) [3,5]. Several factors influence the final chemical struc-ture of the silanes and therefore their properties, such as pH, curing time, aging concentration and chemical structure of the silanes.…”

“…Various techniques to apply a sol-gel coating can be used being the most commonly ones dip-coating and spin-coating, but also spraying and electrodeposition [10]. After the deposition of the coating the materials are subjected to a curing step that can produce the appearance of cracks on the surface due to the contraction of volume and internal stress accumulating during solvent and water evaporation [5,10]. Electrolyte and aggressive species can diffuse through cracks and small defects like pores or scratches on the coatings archiving the metal Surface and starting corrosion processes.…”