Effect of AA2024‐T3 surface pretreatment on the physicochemical properties and the anticorrosion performance of poly(γ‐glycidoxypropyltrimethoxysilane) sol‐gel coating

Abstract

This study investigated the dependence of the anticorrosion performance of a poly(γglycidoxypropyltrimethoxysilane) (poly(γ-GPTMS)) sol-gel coating on AA2024-T3 aluminum alloy surface state. Two different AA2024-T3 surface pretreatment procedures were tested: a degreasing with acetone and a chemical multistep etching process (industrial chemical etching pretreatment). Poly(γ-GPTMS) coatings were deposited onto both pretreated surfaces using the dip-coating technique. Surfaces were characterized principally by scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared attenuated total reflectance, contact angles, and roughness measurements. Moreover, for the coated AA2024-T3 surfaces, a pull-off test was used to evaluate the poly(γ-GPTMS) adhesion to the pretreated surface. Bare surface properties depended on the applied pretreatment. The chemically etched surface was the roughest and the most concentrated in hydroxyl groups. In addition, comparatively to the degreased surface, it has a more hydrophobic character. Poly(γ-GPTMS) coating revealed an uneven nature and a poor adhesion once it was deposited onto the degreased surface. Coatings anticorrosion performances were evaluated using electrochemical impedance spectroscopy measurements (EIS). Electrochemical impedance spectroscopy data proved that the sol-gel coating applied onto the chemically etched surface had better anticorrosion performance.

The effect of surface pretreatment on the corrosion behaviour of silanated AA2198‐T851 Al‐Cu‐Li alloy

“…The enriched surface and the significantly reduced amount of active Mg, Li, and Al (that readily forms hydroxides) resulted in reduced amount of available hydroxyl ions for efficient silanization. The presence of hydroxyl ions metal surfaces strongly favours silanization as hydroxides bond readily with the silanol groups to form MeOSi after curing . On the other hand, for the P and PS samples (Figure C‐D), there were pronounced differences in their EIS behaviours.…”

“…Effects of surface pre‐treatments on different Al alloys before silanization have been previously reported . Franquet and co‐workers were able to show that the best pre‐treatment for an AA1050 alloy prior to silanization was alkaline cleaning in comparison with electropolishing and air‐storage.…”

“…The improved performance of the alkaline cleaned substrate (compared with the other pretreatments) was attributed to the increase in the content of the hydroxyl groups in the surface film. Similarly, Mrad et al also showed that a chemically etched surface produced better silanization on an AA2024 alloy compared with degreasing. The improved performance of the chemically etched surface was also attributed to the presence of hydroxyl group and also to the surface roughness.…”

Green Nanocoatings Based on the Deposition of Zirconium Oxide: The Role of the Substrate

“…In this case, the presence of Al 2 O 3 /AlOOH passivating layers, observed either in AA1100 or in AA2024 samples ( Figure 3 ), are the responsible for the great affinity of water molecules to this surface. Additionally, the etching of the surface with alkaline solution and the formation of oxide-hydroxide layers enhanced the roughness ( Table S1 ) and it is another reason for their high wettability [ 47 , 48 ].…”

Corrosion protection of aluminum alloy by epoxy coatings containing polyaniline modified graphene additives

“…Among them, polyaniline (PANI) coating attracts many attentions. PANI is one of the most important electroconducting polymers due to its good environmental stability, ease of synthesis and relatively low cost . PANI has three basic structures, namely a fully reduced leucoemeraldine base (LEB), a fully oxidized pernigraniline base, and a half‐oxidized/half‐reduced emeraldine base (EB) state.…”