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Hybrid organic–inorganic coatings are deposited on 304 stainless steel substrates by the sol–gel technique to improve the corrosion resistance. A titania-based nanostructured hybrid sol–gel coating is impregnated with three different microencapsulated healing agents (inhibitors) including cerium, Benzotriazole (BTA), and 8-Hydroxyquinoline (8H). Field-emission scanning electron microscopy (FE-SEM) and electrochemical impedance spectroscopy (EIS) are performed to investigate the barrier performance properties. The optimum conditions to achieve corrosion protective coatings for 304 stainless steel were determined. The Nyquist plots demonstrate that the activation time of the coating containing 8H as an organic healing agent shows improved behavior when compared to other coatings including cerium and BTA. Cerium as an inorganic healing agent is second and BTA is third and minimum. An increase in the impedance parameters such as resistance and capacitance as a function of immersion time is achieved in a 3.5wt.% NaCl solution by using healing agents such as BTA. Actually, over the course of immersion, the barrier performance behavior of the coatings changes and reduction of the impedance observed from the coatings containing Ce and 8H discloses deterioration of the protection system after immersion for 96h of immersion in the 3.5% NaCl solution. However, after 96h of immersion time, the concentration of chloride ions is high and causes increase in defects, micro cracks, hole on the surface of hybrid titania nanostructured coating containing Ce and 8H by destruction of coating, and also hybrid titania nanostructured coating containing BTA; BTA is released from coating to improve the resistance of passive film, which is created on the surface.

Aluminum (Al) alloy ships are vulnerable to both damage from chlorine ions in seawater environments and cavitation-erosion due to fast relative motion of metal and liquid resulting from lightweight and high-speed vessels moving through seawater. These corrosive processes cause damage to the hulls of ships, resulting in large economic losses. Recently, cavitation peening technology to improve the durability of a material has been in development. The technology works by forming compressive residual stress on the surface layer of the material in order to improve fatigue strength and fatigue life. In this study, we performed a water cavitation peening (WCP) on a 5083-O Al alloy for ships by applying an ultrasonic piezoelectric effect and cavitation effect, as described in ASTM-G32. From these experiments, we determined an optimum WCP duration, 2.5min, for sufficient cavitation resistance characteristics. This timing improved cavitation resistance by 48.68% compared to the untreated condition. A comprehensive comparison of all of results revealed that the optimum WCP duration was 3min with respect to the point of cavitation and corrosion resistance.

This paper demonstrates the growth of graphene on stainless steel foil by thermal chemical vapor deposition (CVD). Raman spectroscopy confirms that the few-layer graphene with very low deflect can be grown on stainless steel foil. Scanning electron microscope presents that the surface roughness obviously increases after graphene grows on stainless steel resulting in increase in surface area. Energy-dispersive X-ray spectroscopy reveals that there is no oxygen on the graphene surface leading to an increase in its electrical conductivity. The results of the electrochemical test indicate that the growth of graphene on stainless steel can increase corrosion resistance and restrain the formation of passive layer which reduces fuel cell efficiency. Four-point probe measurement confirms that the growth of graphene can also considerably reduce the electrical resistance of stainless steel.

Biocompatibility is crucial for implants. In recent years, numerous researches were conducted aiming to modify titanium alloys, which are the most extensively used materials in orthopedic fields. The application of zirconia in the biomedical field has recently been explored. In this study, the biological ZrO₂ coating was synthesized on titaniumalloy (Ti6Al4V) substrates by a duplex-treatment technique combining magnetron sputtering with micro-arc oxidation (MAO) in order to further improve the corrosion resistance and biocompatibility of Ti6Al4V alloys. The microstructures and phase constituents of the coatings were characterized by scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), the surface wettability was evaluated by contact angle measurements. The results show that ZrO₂ coatings are porous with pore sizes less than 2$\mu$m and consist predominantly of the tetragonal ZrO₂ (t-ZrO${}_2)$ and cubic ZrO₂(c-ZrO${}_2)$ phase. Electrochemical tests indicate that the corrosion rate of Ti6Al4V substrates is appreciably reduced after surface treatment in the phosphate buffer saline (PBS). In addition, significantly improved cell adhesion and growth were observed from the ZrO₂/Zr surface. Therefore, the hybrid approach of magnetron sputtering and MAO provides a surface modification for Ti6Al4V to achieve acceptable corrosion resistance and biocompatibility.

Ni–W–Al₂O₃ nanocomposite coatings were deposited on the low-carbon steel substrates from aqueous sulfate-citrate electrolytes containing various amounts of Al₃O₂ nanoparticles. Their surface morphology, element and phase composition were carried out using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The corrosion resistance was carried out using the potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy (EIS). It is shown that incorporation of Al₂O₃ nano-particles into amorphous Ni–W coating would transform its structure to being crystalline and influence its properties. The hardness sharply increases and corrosion resistance performance significantly decreases even after few Al₂O₃ nanoparticles (2 g/L) were added into the bath. In addition, with increase of Al₂O₃ addition in the bath, a tendency of increase in hardness and corrosion resistance performance is observed.

Chloride ions in seawater can destroy the passive state films on the exposed surface of aluminum (Al) alloy ships. This shortens hull lifespan and increases the maintenance costs of ships. Recently, the water cavitation peening (WCP) technology has been adopted to form compressive residual stress on surfaces to improve resistance to cavitation. This study was conducted to investigate corrosion damage prevention by applying the WCP technology to 5083-O Al alloy for ships; the optimum WCP duration and corrosion protection potential range for maintaining corrosion resistance were determined. We found that the optimum WCP duration was 2.5min by performing a potentiostatic experiment, and the optimum corrosion protection potential range was $-1.30$V–$-0.75$V for ICCP system.

A gradient microstructure was generated on a low-carbon steel/Cr alloy through severe deformation by an impact peening and a recovery treatment. The microstructure was probed by scanning electron microscopy, energy disperse spectroscopy and x-ray diffraction. The microhardness, tensile strength and electrochemical corrosion resistance of the gradient microstructure surface were studied. The material with a fine grain gradient microstructure on the surface had increased microhardness, strength, ductility and corrosion resistance compared to a low-carbon steel standard. When a Cr solution was added, a hard (Fe,Cr)₇C₃ phase was generated, suggesting that Cr alloying plays important roles in these enhanced properties.

The purpose of this paper is to present the corrosion behavior of the Cryorolled (CR) material and its Friction Stir Welded joints. Due to the thermal cycles of Friction Stir Welding (FSW) process, the corrosion behavior of the material gets affected. Here, the cryorolling process was carried out on AA2219 alloy and CR material was joined by FSW process using four different pin tool profiles such as cylindrical, threaded cylindrical, square and hexagonal pin. The FSW joints were analyzed by corrosion resistance with the help of potentiodynamic polarization test with 3.5% NaCl solution. From the analysis, it is found that CR AA2219 material exhibits good corrosion resistance compared to the base AA2219 material, and also a hexagonal pin profile FSW joint exhibits high corrosion resistance. Among the weld joints created by four different tools, the lowest corrosion resistance was found in the cylindrical pin tool FSW welds. Further, the corroded samples were investigated through metallurgical investigations like OM, Transmission Electron Microscopy (TEM), Energy-Dispersive X-ray Spectroscopy (EDX) and X-Ray Diffraction (XRD). It was found that the amount of dissolution of Al₂Cu precipitate was present in the weld nugget. The amount of dissolution of Al₂Cu precipitate is higher in the weld nugget produced by hexagonal pin tool. This is due to the enhancement of the corrosion resistance.

In order to enhance the corrosion resistance of mooring chain, the composite coatings are carried out on the surface of 22MnCrNiMo steel for mooring chain by double-pulsed electrodeposition technology using centrifugal force in the rotating device. The microstructure and anti-corrosion performance of the composite coatings have been investigated experimentally. This paper mainly focuses on the experimental work to determine the structural characteristics and corrosion resistance of composite coatings in the presence of nano-SiC. The results show that the presence of nano-SiC has a significant effect on the preparation of composite coating during the process. The surface of the coating becomes compact and smooth at a moderate concentration of nano-SiC particles. Furthermore, the best corrosion resistance of the composite coatings can be obtained when the concentration of nano-SiC particles is 2.0g.L${}^{-1}$ after salt spray treatment.

Due to the study of marine corrosion of mild steel, in order to simulate the corrosion conditions of enamel coatings in seawater, enamel coatings applied on mild steel were immersed in 3.5wt.% NaCl liquor and the related corrosion features and behavior of enamel were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and evaluated by electro-chemical method such as potentiodynamic polarization testing. Under the appropriate heat treatment system, the enamel coatings sintered on the same kind of mild steel at different temperatures were studied: all enamel samples were within the temperature range from 710${}^{\circ }$C to 830${}^{\circ }$C, the heat treating process at the microstructural level was evaluated and correlated with corrosion resistance properties. All the enamel coatings were characterized and it was observed that the enamel coatings that showed excellent corrosion resistance when sintered at a temperature of 810${}^{\circ }$C can offer a better physical barrier than other temperatures because of their better bonding force and dense microstructure with less pores.

The development of new corrosion-resistant coatings is often challenging, but strongly driven by the potential benefits such coatings hold. A nanostructured Ta₂N coating was deposited on a Ti–6Al–4V substrate in an Ar–N atmosphere using a double cathode glow discharge plasma method with the aim being to improve its corrosion resistance in oral environments. The microstructure of the coating was investigated by a range of methods including XRD, SEM-EDS and TEM. The as-deposited coating exhibited densely packed fibrous structure and the individual fibers were composed of equiaxed grains with an average grain size $\sim 13$nm, arranged along the longitudinal axis of the individual fibers. The electrochemical behavior of the Ta₂N nanocrystalline coating was characterized in artificial saliva containing different NaF concentrations by a range of electrochemical techniques, including potentiodynamic measurement, EIS, capacitance and PZFC measurements. It was shown that the coating possessed superior corrosion resistance compared to uncoated Ti–6Al–4V, because its passive film exhibited higher stability against the fluoride ion attack.

Rare earth has been widely used in materials manufacturing to improve mechanical properties. In this paper, Nano-CeO₂-modified WC/12Co coating with biomodal-sized WC was produced by using high speed oxygen flaming (HVOF) spraying technology. XRD phase analysis showed that the decarburization of WC in coating doped with nano-CeO₂ was slighter than no-doped coating. Potentiodynamic polarization showed that the nano rare earth modifier had improved the corrosion resistance of WC/12Co coating. In addition, long-term immersion in 3.5wt.% NaCl solution was conducted and the surface morphologies after immersed 200h were observed to investigate the corrosion mechanisms. The results showed WC-12Co coatings with 2wt.% nano-CeO₂ possessed better corrosion resistance and the one without nano rare earth was corroded seriously. The positive effect of CeO2 on corrosion resistance of WC/12Co coating can be attributed to the improvement of interfacial strength between Co binder phase and WC particles.

Effects of copper surface roughness $R_{\mathrm{\text{a}}}$ on the properties of Ni–Co–Fe alloy coatings were studied by the measurement of coating roughness, thickness, hardness, substrate/coating bonding force and the potentiodynamic polarization curve. Results showed that at the current density of 4A/dm², the coating roughness increased with the increase of the value of substrate $R_{\mathrm{\text{a}}}$ in the range 0.1–1.1$\mu$m. The coating thickness and hardness increased with the decrease of substrate $R_{\mathrm{\text{a}}}$. When substrate $R_{\mathrm{\text{a}}}$ was 0.4$\mu$m, the substrate/coating bonding force reached the maximum level. When substrate $R_{\mathrm{\text{a}}}$ was 0.1$\mu$m, the coating exhibited the best corrosion resistance. The comprehensive properties of the Ni–Co–Fe coatings can be effectively improved by controlling the surface roughness of copper substrate properly.

A zero-emission electroless nickel plating bath was investigated, which consisted of nickel hypophosphite, hypophosphorous acid, lithium acetate, citric acid and maleic acid. The bath stability, bath life and plating rate were 68.0min, 8 cycles and 13.39$\mu$m/h, respectively. The Ni–P plating layer showed smooth appearance with lots of small continuous nodules, with 12.23wt.% phosphorus content. The electrochemical measurements showed that the deposit exhibited excellent corrosion resistance. All of these properties of the zero-emission plating bath and its deposit were better than those of the popular plating solution and its layer. It is most significant that the spent plating bath can be used directly as a raw material to prepare LiFePO₄/C materials, which conforms to the concept of circular economy.

The corrosion behavior of as-cast AZ91C magnesium alloy was studied by performing friction stir processing (FSP) and FSP followed by solution annealing and then aging. Phase analysis, microstructural characterization, potentiodynamic polarization test and immersion tests were carried out to relate the corrosion behavior to the samples microstructure. The microstructural observations revealed the breakage and dissolution of coarse dendritic microstructure as well as the coarse secondary $\beta$-Mg${}_{17}$Al${}_{12}$ phase which resulted in a homogenized and fine grained microstructure (15$\mu$m). T6 heat treatment resulted in an excessive growth and dispersion of the secondary phases in the microstructure of FSP zone. The potentiodynamic polarization and immersion tests proved a significant effect of both FSP and FSP followed by T6 on increasing the corrosion resistance of the cast AZ91C magnesium alloy. Improve in corrosion resistance after FSP was attributed to grain refinement and elimination of segregations and casting defects which makes more adhesive passive layer. Increase in volume fraction of precipitations after T6 heat treatment is determined to be the main factor which stabilizes the passive layer at different polarization values and is considered to be responsible for increasing the corrosion resistance.

The present work reports the deposition of a quaternary Ni-B-W-Mo coating on AISI 1040 medium carbon steel and its characterization. Quaternary deposits are obtained by suitably modifying existing electroless Ni-B bath. Composition of the as-deposited coating is analyzed by energy dispersive X-ray spectroscopy. The structural aspects of the as-deposited and coatings heat treated at 300${}^{\circ }$C, 350${}^{\circ }$C, 400${}^{\circ }$C, 450${}^{\circ }$C and 500${}^{\circ }$C are determined using X-ray diffraction technique. Surface of the as-deposited and heat-treated coatings is examined using a scanning electron microscope. Very high W deposition could be observed when sodium molybdate is present in the borohydride-based bath along with sodium tungstate. The coatings in their as-deposited condition are amorphous while crystallization takes place on heat treatment. A nodulated surface morphology of the deposits is also observed. Vickers’ microhardness and crystallite size measurement reveal inclusion of W and Mo results in enhanced thermal stability of the coatings. Solid solution strengthening of the electroless coatings by W and Mo is also observed. The applicability of kinetic strength theory to the hardening of the coatings on heat treatment is also investigated. Corrosion resistance of Ni-B-W-Mo coatings and effect of heat treatment on the same are also determined by electrochemical techniques.

The present study was focussed on investigating the corrosion properties of plasma-oxidized and -nitrided CoCrMo alloys under different conditions. The structural properties of untreated and treated samples were examined by using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Corrosion behavior of samples was mainly investigated by potentiodynamic polarization and electrochemical impedance spectroscopy in simulated body fluid solution. The results showed that corrosion resistance of the oxidized layers was better than that of the nitrided ones. The corrosion resistance of the alloys increased as the plasma oxidation process temperature and time increased. However, the corrosion resistance of the alloys reduced with increase in the process temperature and time after plasma nitriding process.

Three different types of current-collecting plates for air-hydrogen PEM fuel cell were manufactured and tested: unmodified titanium plates; gold-plated titanium plates and titanium plates treated by carbon ions implantation. It was shown that the applied surface modifications reduce contact resistance between titanium plate and carbon gas diffusion layer. Total ohmic resistance of fuel cell is reduced by 1.8 and 1.4 times in case of gold-plated titanium and carbon-implanted titanium, respectively, in comparison with uncoated titanium. Although gold plating turned out to be more profitable than carbon ion implantation in terms of electrical characteristics, in the last case, the performance enhancement was reached without using precious metals, which at mass production must play more important role. This technology promises to reduce the cost of bipolar plates manufacturing, while maintaining high electrical performance of PEM fuel cells.

A carbon precursor film was formed on a titanium plate by a hydrothermal method using glucose, and an amorphous film was obtained by carbonization at 400^∘C under an Ar atmosphere. The morphology and composition of the surface was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), and the interface contact resistance (ICR) under different pressures by simulating the working mode of the fuel cell. The corrosion resistance of amorphous carbon coatings was tested by simulating the proton exchange membrane fuel cells (PEMC). The amorphous coating showed excellent interfacial conductivity and great corrosion resistance, with high potential application in bipolar plates of PEMFCs

In this work, TiAlV thin films have been prepared on two different types of substrates: silicon and stainless steel (SS304) by two deposition methods: Pulsed Laser Deposition (PLD) and DC magnetron sputtering. Different techniques have been employed in order to characterize film properties such as: Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-ray (EDX), X-ray diffraction (XRD), microhardness and corrosion test. EDX analysis showed that the deposited films are slightly different from that of the target material Ti6Al4V alloy. The measured microhardness values are about 11.7GPa and 4.7GPa for films prepared by PLD and DC magnetron sputtering, respectively. Corrosion test indicated that the corrosion resistance of the two TiAlV films deposited on SS304 substrates in (0.9% NaCl) physiological normal saline medium was significantly improved compared with the SS304 substrates. These attractive results could permit applications of our films in the medical implants fabrication.