Corrosion protection of carbon steel by silica-based hybrid coatings containing cerium salts: Effect of silica nanoparticle content

Abstract

One strategy for minimising corrosive attack on carbon steel involves the application of hybrid coatings rich in rare earths, on the basis of their low toxicity and environmental sustainability. Tetraethoxysilane (TEOS) and 3-glycidoxypropyl-trimethoxysilane (GPTMS) were each used here as precursors, together with various quantities of colloidal silica suspension, to improve barrier properties of the coatings. Ce(NO3)(3)center dot 6H(2)O was added as a source of Ce(III) for further inhibition of corrosion. The corrosion resistance of each kind of sample was evaluated using potentiodynamic polarisation measurements and electrochemical impedance spectroscopy (EIS) in 0.35 wt.% NaCI solution. The electrochemical behaviour at various immersion times was modelled by equivalent circuits to demonstrate the effect of silica nanoparticle loading on corrosion. Additional testing was performed under harsh conditions of salt spray chamber. The microstructure and composition of sol-gel coatings were characterised by scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDS), focused-ion beam SEM/EDS analysis, X-ray photoelectron spectroscopy and confocal microscopy. (C) 2015 Elsevier B.V. All rights reserved.Postprint (published version

Self-Healing Effect of Hybrid Sol-Gel Coatings Based on GPTMS, TEOS, SiO2Nanoparticles and Ce(NO3)3Applied on Aluminum Alloy 7075-T6

“…16,[40][41][42] Namely, the inhibition effect was observed, but a fast deterioration of the barrier properties of the coating occurred after 24 hours in 0.35 wt% NaCl.…”

“…40,41 When using monolayer sol-gel coating doped with cerium to obtain barrier and active protection, the long-term coating stability can be jeopardized. 16,[40][41][42] Namely, the inhibition effect was observed, but a fast deterioration of the barrier properties of the coating occurred after 24 hours in 0.35 wt% NaCl.…”

“…40,41 When using monolayer sol-gel coating doped with cerium to obtain barrier and active protection, the long-term coating stability can be jeopardized. 16,[40][41][42] Namely, the inhibition effect was observed, but a fast deterioration of the barrier properties of the coating occurred after 24 hours in 0.35 wt% NaCl.16 A multi-layer sol-gel hybrid coating, based on TEOS, methacryloxypropyl trimethoxysilane (MPS), ethylene glycol dimethacrylate (EGDMA) and glycidyl methacrylate (GMA) containing an intermediate cerium doped layer was shown to greatly improve the corrosion properties of AA2024.32 It was further showed that the barrier and active protection of coatings were improved in multi-layer coating, based on TEOS, GPTMS and SiO 2 nanoparticles, where cerium was in the top layer, but the self-healing ability of such coatings applied on carbon steel was not confirmed. 16 In the present work three types of multi-layer hybrid sol-gel coatings were developed based on the inorganic precursor TEOS, organic precursor GPTMS, SiO 2 nanoparticles and corrosion inhibitor Ce(NO 3 ) 3 .…”

“…Addition of silica nanoparticles (SiO 2 ) into sol-gel coating has been reported to additionally increase the barrier effect by increasing the coating thickness, density and reinforcement. [16][17][18][19][20][21][22][23] Still, if these coatings do not contain corrosion inhibitors they lack the ability to inhibit the corrosion process once it commences, i.e. they do not show active inhibition ability resulting in a self-healing of the coating.…”

“…16 In the present work three types of multi-layer hybrid sol-gel coatings were developed based on the inorganic precursor TEOS, organic precursor GPTMS, SiO 2 nanoparticles and corrosion inhibitor Ce(NO 3 ) 3 . The aim was to develop a coating system that would prevent the leaching of cerium ions from the coating.…”