Anticorrosion Properties of a Novel Hybrid Sol-Gel Coating on Aluminum 3003 Alloy

In this study, a novel hybrid sol–gel coating on AA3003 substrate was developed and the effects of various waste material additives on the reinforcement of the sol–gel coating and the anticorrosion properties in the saline medium were investigated. Egg shell, crumb rubber, activated carbon obtained for pyrolysis of waste rubber tire, waste rubber tire, cement kiln dust, and ST100 additives were tested as reinforcement materials. The AFM characterization results of the coating formulations on AA3003 alloy revealed enhanced roughness values for the modified coatings as compared to the base coating. Similarly, no significant changes were detected in the Fourier transform infrared spectroscopy (FTIR) absorption peaks of the hybrid polymeric material upon loading it with the waste additives, while slight changes in the hydrophobic properties of the final modified coatings were observed as a result of the modification process. Electrochemical impedance spectroscopy (EIS) results revealed that the hybrid sol–gel coating had a promising potential for the protection of the AA3003 substrate against corrosion in the saline medium. However, the loaded additives negatively affected the corrosion resistance properties of the parent hybrid sol–gel coating. For instance, the egg shell additive had the least negative effect on the barrier properties, whereas the cured coating layer of the sample loaded with cement and clay additives showed some disintegration, inhomogeneity, and low barrier properties on the metal surface.

A Novel Electroactive Imide Oligomer and Its Application in Anticorrosion Coating

A novel aniline tetramer (AT) capped electroactive imide oligomer (EIO) for metal corrosion protection was successfully synthesized in this study. The chemical structure of the EIO was characterized by liquid chromatography-mass spectrometry and Fourier-transform infrared spectroscopy. Furthermore, the redox behavior of EIO was identified using electrochemical cyclic voltammetry studies. An EIO coated on a cold-rolled steel (CRS) electrode was found to possess superior corrosion resistance to polyimide (PI) on a series of electrochemical corrosion measurements in 3.5 wt.% NaCl solution over an extended period (30 days). The mechanism for the advanced corrosion protection of the PI coating on the CRS electrode could be attributed to the redox catalytic capabilities of the AT units present in the EIO. These capabilities may induce the formation of passive metal oxide layers on the CRS electrode. Scanning electron microscopy and X-ray photoelectron spectroscopy were used to analyze the surface condition of the CRS after the corrosion test. EIO- and PI-coated electrodes were identified by a series of electrochemical measurements, including corrosion potential (E_corr), polarization resistance (R_p), and corrosion current (I_corr) measurements, along with electrochemical impedance spectroscopy (EIS).

Preparation and properties of gelatin hydrolysate modified with polysiloxane quaternary ammonium salts

PSiQAEp-GH polymers were synthesized by the reaction of gelatin hydrolysate (GH) and polysiloxane quaternary ammonium salts containing epoxy group (PSiQAEp) with different molecular weight from 3147 to 12996. The results of FTIR, ¹H NMR and ¹³C NMR showed that the reaction occurred between primary amino group of arginine in GH and epoxy of PSiQAEp. The XRD and DSC studies showed that the degree of short-range order of PSiQAEp-GH reduced and its glass transition temperature (Tg) lowered more than 10 °C compared with GH. The determinations of moisture absorption and contact angle (CA) indicated that the hydrophobility of PSiQAEp-GH was better than GH. The tests of inhibitory zone and minimum bactericidal concentration (MBC) illustrated that the PSiQAEp-GHs exhibited excellent antibacterial activity, and the antibacterial activity depended on both the chemical structure of PSiQAEp-GHs and the biological structure of the bacteria.

Anticorrosive and physicochemical properties of modified phosphate pigments

Many studies have been carried out in the direction of improvement of the effectiveness of commonly utilized phosphate corrosion inhibitors. For this purpose various types of modifications are realized, e.g. introduction of different cations to the pigment composition or replacement of phosphate anions with others. In the presented work, anticorrosive pigments containing calcium hydrogen phosphate, and/or calcium hydroxyphosphate, and calcium molybdate were obtained. The phase and chemical composition and the oil absorption number of those materials were determined. The anticorrosive properties were investigated by an electrochemical noise method. The obtained results were compared with previously published studies concerning pigments containing (NH4)3Al2(PO4)3 and/or AlPO4, and CaMoO4. It was found that the pigment containing only calcium molybdate(VI) is not an effective corrosion inhibitor. However, the pigments comprising a mixture of CaHPO4 and CaMoO4 exhibited good anticorrosive properties and they were characterized by higher effectiveness in the corrosion protection than compared materials.

Ultrasound-assisted synthesis of zinc molybdate nanocrystals and molybdate-doped epoxy/PDMS nanocomposite coatings for Mg alloy protection

Zinc molybdate (ZM) is a safer anticorrosive additive for cooling systems when compared with chromates and lead salts, due to its insolubility in aqueous media. For most molybdate pigments, their molybdate anion (MoO₄^-2) acts as an anionic inhibitor and its passivation capacity is comparable with chromate anion (CrO₄^-2). To alleviate the environmental concerns involving chromates-based industrial protective coatings, we have proposed new alternative in this work. We have synthesized ZM nanocrystals via ultrasound-assisted process and encapsulated them within an epoxy/PDMS coating towards corrosion protection. The surface morphology and mechanical properties of these ZM doped epoxy/PDMS nanocomposite coatings is exhaustively discussed to show the effect of ZM content on protective properties. The presence of ZM nanocrystals significantly contributed to the corrosion barrier performance of the coating while the amount of ZM nanocrystals needed to prepare an epoxy coating with optimum barrier performance was established. Beyond 2 wt% ZM concentration, the siloxane-structured epoxy coating network became saturated with ZM pigments. This further broadened inherent pores channels, leading to the percolation of corrosion chloride ions through the coating. SEM evidence has revealed proof of surface delamination on ZM3 coating. A model mechanism of corrosion resistance has been proposed for ZM doped epoxy/PDMS nanocomposite coatings from exhaustive surface morphological investigations and evidence. This coating matrix may have emerging applications in cooling systems as anticorrosive surface paints as well as create an avenue for environmental corrosion remediation.

Effect of CNT/PDMS Nanocomposites on the Dynamics of Pioneer Bacterial Communities in the Natural Biofilms of Seawater

In this study, the antifouling (AF) performance of different carbon nanotubes (CNTs)-modified polydimethylsiloxane (PDMS) nanocomposites (PCs) was examined directly in the natural seawater, and further analyzed using the Multidimensional Scale Analyses (MDS) method. The early-adherent bacterial communities in the natural biofilms adhering to different PC surfaces were investigated using the single-stranded conformation polymorphism (SSCP) technique. The PCs demonstrated differences and reinforced AF properties in the field, and they were prone to clustering according to the discrepancies within different CNT fillers. Furthermore, most PC surfaces only demonstrated weak modulating effects on the biological colonization and successional process of the early bacterial communities in natural biofilms, indicating that the presence of the early colonized prokaryotic microbes would be one of the primary causes of colonization and deterioration of the PCs. C6 coating seems to be promising for marine AF applications, since it has a strong perturbation effect on pioneer prokaryotic colonization.

Probing the corrosion inhibiting role of a thermophilic Bacillus licheniformis biofilm on steel in a saline axenic culture

The adhesion of denseBacillus licheniformis(thermophilic strain) biofilm on stainless steel has been found to inhibit corrosion in saline medium up to 90% inhibition efficiency for double the concentration of bacterial cells after 3 weeks.