Iranian Journal of Oil and Gas Science and Technology

Abstract In this study, nanostructured homogeneous and functionally graded (FG) Ni-Co/SiC coatings were fabricated on aluminum substrates via electrodeposition using a square pulse current. The FG coating was produced by continuously varying the concentration of SiC particles (0–40 g/L) in the electrolyte, resulting in a graded particle distribution across the coating thickness. The microstructure and morphology of the coatings were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Mechanical and electrochemical properties were evaluated through microhardness testing, T-peel adhesion testing, pin-on-disk wear testing, erosion testing, and potentiodynamic polarization and impedance spectroscopy. The results revealed that the SiC content in the FG coating gradually increased from 0 wt.% at the substrate interface to 6 wt.% at the surface. Compared to the homogeneous Ni-Co/SiC coatings, the FG coating demonstrated 40% higher adhesion strength and twice the wear resistance. Additionally, the FG coating exhibited improved corrosion resistance and overall mechanical performance, highlighting its potential for demanding industrial applications.

Abstract In this paper, graphene oxide decorated with cerium oxide (CeO₂) nanoparticles was prepared and used as anticorrosive pigments in epoxy nanocomposite coatings. The synthesized nanoparticle was characterized by FTIR, XRD, SEM, and EDX analyses. Graphene oxide decorated with CeO₂ nanoparticles was dispersed in epoxy resin by sonication. The optimum nanoparticle content of the epoxy resin was studied by differential scanning calorimetry. The anticorrosive properties of these coatings were investigated using electrochemical impedance spectroscopy method and polarization in corrosive solution. Impedance parameters showed a decrease in the coating resistance over immersion time. The results indicated that the epoxy coatings containing nanoparticles could significantly increase the corrosion resistance of composite coatings compared to those of pure epoxy, and the highest value was obtained for 1% nanocomposite coatings after 270 days of immersion. Pull-off adhesion test showed that the highest value of adhesion was related to the coating containing 1% nanoparticles.

Abstract Different amounts of nanoclay were incorporated into the acrylic resin matrix at 0, 1, 3, and 5 wt.% loadings. The coatings were applied on low carbon steel plates. Optical microscopy, sedimentation test, transmission electron microscopy, and X-ray diffraction were employed to investigate the dispersion of nanoclay in matrix. The corrosion resistance of coatings was evaluated by electrochemical impedance spectroscopy, polarization measurement, and salt spray test. In addition, pull-off and cross-cut tests were used for the assessment of coating adhesion to the substrate. The results indicated that the anti-corrosive properties of the acrylic resin were obviously increased by the addition of nanoclay. The nanocomposite coatings containing 3 wt.% clay showed the best corrosion resistance. Finally, the nanocomposites containing 1 and 3 wt.% showed the highest adhesion to the substrate.

Abstract As an alternative to chromate conversion coatings, rare-earth coatings especially cerium, because of the low toxicity, have attracted considerable attention. Using dip immersion method, cerium-based conversion coating was deposited on aluminum 2024. Corrosion resistance was studied in 3.5 wt.% NaCl solution using potentiodynamic polarization, electrochemical impedance spectroscopy, and surface methods. The coated samples revealed a considerable decrease in corrosion rate and with increasing immersion time up to 1200 s, the coating resistance increased. Electrochemical impedance data showed that the aluminum charge transfer resistance was increased in the existence of cerium oxide conversion coatings. Using energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM), the chemical composition and surface morphology were also evaluated.

Abstract In this study, nanocomposite coatings based on polyurethane cerium nitrate montmorillonite (MMT) were prepared, applied on carbon steel substrates, and investigated. The nanocomposite coatings were successfully prepared by the effective dispersing of nanoparticles in polyurethane resin by mechanical and sonication processes. The state of dispersion, dissolution, and incorporation were characterized by optical microscopy, sedimentation tests, and transmission electron microscopy. The structure and properties of the nanocomposite coatings were investigated by X-ray diffraction and anticorrosive properties of the nanocomposites were studied by Tafel polarization measurements. The experimental results showed that the PU/MMT/Cerium nitrate nanocomposite coatings were superior to the neat PU in corrosion protection. In addition, it was observed that the corrosion protection of the nanocomposite coatings was improved as the clay and cerium nitrate loadings were increased to 4 wt.% to 2 wt.% respectively.

Abstract The enormous demands for metal implant have given rise to a search for cheap material with good bio-tolerability and resistance to corrosion. Although stainless steel has these properties and is widely used for this purpose, its long term application is still a concern. The corrosion resistance of stainless steel depends on the passive layer. Herein, chemical surface treatment, including passivation, electropolishing, and acid cleaning is used for improving the corrosion-resistance property of AISI 316L and 304L. Cyclic polarization, electrochemical impedance spectroscopy, and EDX analysis were used to investigate the properties obtained thereby. Finally, the corrosion resistance of the untreated and modified specimens was compared. The results show that the corrosion behavior of the passivated and electropolished specimens is improved.

Abstract In this study, the corrosion resistance of a bituminous coating reinforced with different ratios of nanoclay pigment was studied. To make nanocomposite coatings, 2, 3, and 4 wt.% of clay (Cloisite Na+) were incorporated into water emulsified bitumen. The coatings were applied to steel 37. Optical microscopy and X-ray diffraction (XRD) were used to characterize the nanocomposite structure. In order to investigate the anticorrosion behavior of the coatings, electrochemical impedance spectroscopy (EIS) and direct current polarization techniques were used. The results show that the coatings containing nanoclay have better performance compared to the neat bitumen. Moreover, it was revealed that the corrosion resistance of the nanocomposite increased as the clay loading increased up to 4 wt.%.