Corrosion Performance Of Coatings Research Articles

Study on nanocrystalline coating prepared by electro-spraying 316L metal wire and its corrosion performance

Abstract In this work, we study the corrosion performance of coatings prepared by electrical explosion spraying of metal wires. 316L metal wire with a diameter of 1.5 mm is used as spray material, and the coating is prepared on the 45# steel substrate by electrical explosion spraying. The oil–water corrosion experiment of the coating is carried out in a constant temperature water bath of 60°C for 168 h. The scanning electron microscopy and energy-dispersive spectroscopy results of the experimental samples have shown that some metal oxides are found inside the coating, most of which are distributed at the grain boundaries with a size range of 30–50 nm. The corrosion rate of the coating is measured by weight loss method with a corrosion rate of 0.079 mm/annum. XRD results show that the corrosion generates CaCO3, Fe3O4, and MgFe2O4. Coating corrosion is mainly caused by the formation of electrochemical corrosion between oxides and non-oxides in the coating, and pitting corrosion and intergranular corrosion in the presence of chloride ions.

An Impact of the Recent Developments in Coating Materials and Techniques on the Corrosion Response of AZ91D Alloy: A Review

AZ91D, a die‐casted alloy, offers several benefits (better saltwater corrosion resistance, suitable castability, and good atmospheric stability) over other grades of magnesium alloy. However, it cannot overcome the challenging requirements of advanced applications in its current form. Extensive research in coating technologies is crucial in enhancing the performance of AZ91D alloy in highly corrosive environments (coastal and marine, industrial, farm, etc.). The high corrosion resistance of AZ91D for various applications is achievable through the deposition of different materials. Developments in coating materials and techniques, with their influence on the corrosion protection behavior of AZ91D alloy, over the last decade (2012–2022), are focused on in this study. It is observed that composite, biodegradable, and self‐healing coatings are gaining popularity. The transition in the coating technology, from conventional to self‐healing coating materials and from conventional to environment‐friendly coating techniques, is a vital part of this discussion. This review further explores how different additives, pre‐treatments, post‐treatments, and corrosion inhibitors affect the corrosion performance of coatings. This study helps select the optimum coating material for AZ91D magnesium alloy to fulfil a specific application requirement and guides toward technological developments in this segment.

Optimization of the corrosion performance of Ni-SiC coatings through flash heating

Flash heating is an effective thermal deposition technique for additively applying high performance coatings with the possibility of on-site coating application. This research analyzes the corrosion performance of coatings developed by flash heating using a two-cubed full factorial design of processing conditions such as gas flow rate, coating composition, and current on corrosion rate. Using a 95 % confidence interval, it was found that the gas flow rate and the combination of composition and current had statistically significant effects on corrosion performance with p-values of 0.0015 and 0.0067, respectively. The optimal corrosion performance was found to occur at a gas flow rate of 12–14 cfh, composition of 70 wt% Ni and 30 wt% SiC, and a plasma current of 140 A. These parameters resulted in a corrosion rate of 20.4 μA/cm2. This is a reduction of 96.6 % compared to the carbon steel substrate and 90.9 % compared to the worst-performing Ni-SiC coating in terms of corrosion rate. This research enables the prediction and optimization of corrosion performance of Ni-SiC coatings when fabricated by flash heating.

Investigation of thermally sprayed NiCrAlY/TiO2 and NiCrAlY/Cr2O3/YSZ cermet composite coatings on titanium alloys

The present work investigates the hot corrosion behavior of thermally sprayed 65 pct NiCrAlY + 35 pct TiO2 and 65 pct NiCrAlY + 30 pct Cr2O3 + 5 pct YSZ coatings on titanium 15 alloys. The coatings on the titanium 15 alloy substrates exhibit a near-uniform, dense, and adherent microstructure with a porosity of 2.7 to 2.9%. Thermogravimetric studies are made to examine the hot corrosion performance of coatings in a molten salt environment of Na2SO4 + 60%V2O5 at the temperature of 700 °C for 50 cycles. One cycle is carried out by heating for a period of one hour and cooling the sample at ambient conditions. The corrosion products are analyzed based on scanning electron microscopy, energy dispersive analysis, and X-ray diffraction techniques to study the morphology, phase composition, and abundance of the high-temperature corrosion constituents. The bare titanium-15 alloy, 65 pct NiCrAlY + 35 pct TiO2 coating and 65 pct NiCrAlY + 35 pct Cr2O3 + 5 pct YSZ coating produced a weight gain of 307.92 mg cm−2, 42.16 mg cm−2 and 44.02 mg cm−2 respectively after the period of 50 cycles. The effective resistance of the coatings is due to the formation of Ni3V2O8, NiCr2O4, Cr2O3 & AlV2O4 phases.

Assessment of durability and zinc activity of zinc-rich primer coatings by electrochemical noise technique

The three-coat system consisting of a zinc-rich primer, epoxy midcoat, and polyurethane topcoat has been widely adopted for corrosion protection of structural steel bridges. Corrosion mitigation is afforded by the barrier characteristics of the various layers as well as beneficial galvanic coupling of the zinc pigments in the primer to the steel substrate when subjected to corrosive environments such as with moisture ingress and coating defects. The dispersed zinc pigments in the binder require adequate electronic coupling in order to provide the beneficial electrochemical coupling of the zinc to the steel. The application of the electrochemical noise (EN) technique to identify coating corrosion performance was reviewed in controlled laboratory tests. Zinc pigment activation and transition to passive-like conditions in defect and defect-free coating specimens could be identified by EN. The characteristic charge of noise events resolved by shot noise analysis was demonstrated to be related to anodic polarization of extended active zinc pigments adjacent to coating defect sites galvanically coupled to the exposed steel and passivated zinc pigments. Electrochemical noise resistance was shown to convey zinc/steel interfacial behavior in cases with sufficient activity but largely reflects coating barrier quality for intact coatings.

Effect of Molybdate on Corrosion Performance of Oxide Coating Produced on 7075 Al Alloy Using PEO

In this research, plasma electrolytic oxidation (PEO) coatings were prepared on 7075 Al alloy in a silicate-based solution with Na2MoO4 additive using a unipolar waveform at constant current density. The coatings displayed micro-pores, micro-cracks, pancake-like and crater-like features, and also solidified molten oxide particles on the surface. The coatings were majorly composed of Al2O3 (γ, δ, and α), SiO2 (amorphous), and MoO3 phases, which confirms the incorporation of molybdenum in the case of additive-containing coatings. Molybdenum species were transported through cracks, channels, and micropores, as the ready access pathways into the coating and partly sealed the coating pores. The EIS technique was used to evaluate the long-term corrosion performance of the coatings up to 168 h of immersion in 3.5 wt.% NaCl solution. The results showed that the barrier action of the PEO coatings was highly enhanced by adding Na2MoO4 due to the higher resistance that alumina achieved to chlorine absorption and also its higher stability by the incorporation of MoO3. The coating formed in the presence of 5 g L−1 Na2MoO4 showed the highest thickness and the lowest porosity percent (15.15%), which provided the highest corrosion performance at long immersion times.

Wettability and corrosion performance of arc-sprayed Fe-based amorphous coatings

Amorphous coatings (ACs) with the composition of Fe49.7Cr18Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 were deposited by the arc-spraying technique. The wettability and corrosion performance of Fe-based ACs in 3.5% NaCl solution were investigated using contact angle measurements and electrochemical tests, respectively. Results showed that by controlling the spraying potential, the phase constituent, microstructure, hardness, wettability, and corrosion performance of the coatings were manipulated. With a spraying potential of 26 V, the highly glassy AC exhibited a denser microstructure, higher microhardness, lower surface free energy, and better corrosion resistance than the others. The superior corrosion resistance of the coatings was closely related to the surface hydrophobicity, which was dominantly governed by the microstructure of the coatings. This finding demonstrates the importance of a homogeneous and compact structure for anti-corrosion and provides a quick prediction of corrosion performance among ACs.

Corrosion properties and surface free energy of the Zn[sbnd]Al LDH/rGO coating on MAO pretreated AZ31 magnesium alloy

Micro-arc oxidation (MAO) is one of the promising surface treatment methods that can enhance the corrosion resistance of magnesium alloys. However, the existence of pores and microcracks significantly restricts the further advancement of corrosion resistance. In this study, effective and environmentally friendly materials, layered double hydroxides (LDH), with and without combination of rGO (reduced graphene oxide) nanosheets, were employed to seal the pores and micro-cracks in order to enhance the anti-corrosion and degradation performance of the MAO coating on AZ31. Microstructural morphologies and crystallography of the coatings were characterized using scanning electron microscopy (SEM), and X-ray diffraction (XRD). The corrosion performances of coatings were investigated by an electrochemical workstation. Moreover, hydrophobicity and surface free energy of the synthesized coatings were measured by sessile drop method. The characterization results demonstrated that incorporation of the GO sheet with ZnAl LDH flakes could effectively enhance the anti-corrosion properties (iCorr = 5 nA/cm2) and long-term degradation of the MAO coating. Furthermore, the GO plates were reduced to rGO during the hydrothermal process, which further improves the hydrophilicity and lowers the surface free energy of the coatings, i.e. γMAO−LDH/rGOs=17.8mNm<γMAO−LDHs=24.7mNm<γMAOs=43.1mNm.

CHARACTERIZATION AND ELECTROCHEMICAL CORROSION ANALYSIS OF HEAT-TREATED REINFORCED HA COATINGS DEPOSITED BY VACUUM PLASMA SPRAY TECHNIQUE

Herein, a biomimetic coating of hydroxyapatite (HA)–Al2O3 and HA–ZrO2 was deposited on Ti–6Al–4V-alloy using vacuum plasma spray (VPS) technique. The bond-coat of ZrO2 has been introduced between the substrate and reinforced HA coatings to study the effect of bond-coat on structural, mechanical properties and electrochemical corrosion performance of the developed coatings. In addition, the impact of thermal treatment of coating was investigated on these properties too. Coating characteristics, such as morphology, porosity, surface roughness, and crystallinity were investigated. The corrosion performance of coatings was tested in Hank’s-based salt solution (HBSS). Significant enhancement in crystallinity and surface-hardness has been witnessed after heat treatment; nevertheless, porosity reduced. The electrochemical corrosion study revealed that the corrosion resistance of heat-treated samples was better than the as-sprayed coatings samples. The intensity of XRD peaks of all coatings increased after 24[Formula: see text]h immersion in HBSS for the electrochemical test in comparison to the intensity of peaks before the corrosion test.

Corrosion Performance of Electrodeposited Zinc and Zinc-Alloy Coatings in Marine Environment

Electrodeposited zinc and zinc-alloy coatings have been extensively used in a wide variety of applications such as transport, automotive, marine, and aerospace owing to their good corrosion resistance and the potential to be economically competitive. As a consequence, these coatings have become the industry choice for many applications to protect carbon and low alloy steels against degradation upon their exposure in different corrosive environments such as industrial, marine, coastal, etc. Significant works on the electrodeposition of Zn, Zn-alloys and their composites from conventional chloride, sulfate, aqueous and non-aqueous electrolyte media have been progressed over the past decade. This paper provides a review covering the corrosion performance of the electrodeposited Zn, Zn-alloy and composite with different coating properties that have been developed over the past decade employing low-toxic aqueous and halide-free non-aqueous electrolyte media. The influence of additives, nano-particle addition to the electrolyte media on the morphology, texture in relation to the corrosion performance of coatings with additional functionalities are reviewed in detail. In addition, the review covers the recent developments along with cost considerations and the future scope of Zn and Zn-alloy coatings.

Preparation of α-Fe2O3@TA@GO composite material and its anticorrosion performance in epoxy modified acrylic resin coatings

Adding organic-inorganic composite materials is a common way to improve the anti-corrosion performance of organic coatings. In this study, tannic acid as a bridge was first modified with the mica iron oxide, and then reacted with the carboxyl group on the surface of graphene oxide. Mica iron oxide @ tannic acid @ graphene oxide (α-Fe2O3@TA@GO) composite materials were prepared and characterized by infrared spectroscopy, x-ray diffractometer, x-ray photoelectron spectrometer, and scanning electron microscope. The modified products showed good dispersion stability in water, and the sedimentation time was increased from 3 h to 24 h. Composite materials were doped in waterborne epoxy modified acrylic to manufactured coatings. The electrochemical workstation was used to evaluate the corrosion performance of coatings. It was found that the corrosion resistance of the paint film could be greatly improved by adding composite materials characterized by Potentiodynamic polarization curves and EIS analysis. The optimal corrosion resistance can be obtained by adding 5wt% α-Fe2O3@TA@GO fillers. The corrosion current density (icorr) was 1.459 μA/cm2 and the charged transfer resistance (Rct) was up to 14350 Ω cm2, which was shown good potential as anti-corrosive fillers in coatings.

Effects of CeO² on Microstructure and Corrosion Performance of the Coatings Prepared by Pulse Micro Arc Oxidation on AZ31B Mg Alloy.

To improve corrosion performance of coatings on AZ31B magnesium alloy, the nano-CeO² additives were included in Na²SiO³ based electrolyte during process of pulse micro arc oxidation (MAO). The MAO-CeO² coating was successfully prepared to characterize its structure, micro morphology and composition. The XRD results indicated that MAO-CeO² coatings were consisted of Mg²SiO⁴, MgSiO³, MgF² and CeO². The intensity of CeO² peaks increases with increasing nano-CeO² particles in electrolyte. The number of cracks on MAO-CeO² coatings exhibited a V-shaped trend with increase in nano-CeO² content. Meanwhile, the influence of nano-CeO² on corrosion behavior of MAO-CeO² coatings is investigated by salt spray test and electrochemical measurement. The corrosion current density of coatings presented same trend and corrosion potential is further studied. The MAO-CeO² coatings formed in electrolyte with 10 g/L nano-CeO² showed best corrosion performance which has the lowest corrosion current density of 0.58 nA/cm² and the highest corrosion potential of - 1269 mVSCE.

Effect of graphene addition on composition, morphology and corrosion behavior of ZnNiFe-graphene composite coatings

Graphene reinforced, Zn-rich, Zinc-Nickel-Iron (ZnNiFe-G) coatings were deposited on mild steel substrate by electrolyzing the Zn-Ni-Fe acidic sulphate bath containing different amounts of dispersed graphene layers. Effect of graphene incorporation on composition, microstructure, morphology and electrochemical corrosion performance of coatings was investigated. X-ray diffraction studies revealed ZnNiFe coatings consists η Zn, γ Ni2Zn11 and Fe phases but the concentration of γ Ni2Zn11 phase increased with increasing graphene content in the coating. Incorporation of graphene enhanced the coating compactness and reduced the micro-pores and surface defects. Presence of graphene increased the Ni and Fe content in the coatings. The electrochemical corrosion behavior of the composite coatings was determined using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Increase in γ Ni2Zn11 phase concentration, compact and defect free ZnNiFe-G composite coatings exhibited >50% better corrosion resistance performance when compared to the corrosion resistance exhibited by the graphene free Zn-Ni-Fe coating. Among the ZnNiFe-G coatings, the composite coating with combination of highest Ni and graphene content showed the best corrosion resistance performance.

Grain boundary engineering in Ni-carbon nanotube composite coatings and its effect on the corrosion behaviour of the coatings

Coatings have been traditionally used for protection against corrosion. One possible way to enhance the corrosion resistance performance of coatings is by grain boundary engineering (GBE). This study illustrates the role of optimum amount of carbon nanotubes (CNTs) in modifying the grain boundary constitution in nickel-CNT composite coatings thereby enhancing its corrosion resistance performance. Compact and crack free Ni-CNT composite coatings were electrodeposited on mild steel substrates using electrolyte bath with different concentrations of dispersed CNTs (4, 6, 8, 10, 20, 30, 40, 50, 70 and 100 mg/L). Corrosion performance of coatings exposed to 3.5 wt.% NaCl medium was studied by potentiodynamic polarisation and electrochemical impedance spectroscopy techniques. Among the 10 different Ni-CNT composite coatings, relatively low corrosion rates were observed for two distinct CNTs concentrations. Microstructural characterization conducted using the electron back scatter diffraction method (EBSD) suggested that the grains in all coatings grew with 〈110〉 orientation. Ni-CNT3 coating (from 8 mg/l of CNT in electrolyte) which showed low corrosion rate (corrosion current density of 0.98 µA/cm2) primarily contained very high fraction of low angle grain boundaries. Ni-CNT8 coating (from 50 mg/l of CNT in electrolyte) which exhibited the lowest corrosion rate (corrosion current density of 0.66 µA/cm2) contained high fraction of Σ3 coherent twins. Ni-CNT10 coating (from 100 mg/l of CNT in electrolyte) which exhibited the highest corrosion rate (corrosion current density of 14.08 µA/cm2) contained random high energy high angle grain boundaries (HAGBs) along with high energy symmetrical and asymmetrical tilt boundaries.

The tribological and corrosion behavior of TiO2 coatings deposited by the electrophoretic deposition process

TiO2 coatings have recently been used as corrosion resistant materials to protect metals in several environments. In this study, the microstructure, phase composition and morphology under different voltages (20, 30 and 40 V) were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. The coating corrosion performance was examined by potentiodynamic polarization in 3.5 wt% NaCl solution. Experimental findings indicate that the thickness and cracks of the coating rise by increasing voltage. Energy dispersive X-ray spectroscopy results show that the atomic ratio Ti/O of the coating has an almost constant ratio. Obviously, the defects and cracks on the deposited coatings resulted in corrosive attack due to a considerable increase of the corrosion current density noticed during potentiodynamic polarization experiments. The film produced under 30 V exhibited the lowest corrosion current density [Formula: see text] value of 0.21 µA cm−2 as well as the lowest corrosion potential ([Formula: see text] value of −111.89 mV, which was attributed mainly to the significant decrease of micro-pore density in the coating.

Fe–Ni composite coatings reinforced with SiC nanoparticles and carbon nanotubes: corrosion and tribological performance

The fabrication of electrodeposited Fe-Ni composite coatings reinforced by SiC nanoparticles and multi-wall carbon nanotubes (MWCNT) separately was studied in this research. For this aim, the electrodeposition method was performed in a sodium chloride bath at a current density of about 10 A dm−2. The specimen’s phase and microstructure was investigated by XRD and SEM analysis, respectively. The wear and corrosion performances of coatings were also inspected using pin-on-disk (at ambient atmosphere) and Potentiaodynamic test techniques, respectively. The results point out that the electrodeposition method can be used to deposit Fe-Ni composite coatings containing SiC and CNT on a steel substrate. The results show that the presence of SiC nanoparticles in the coating matrix caused an improvement in the corrosion resistance of this coating as compared to that of Fe–Ni coat. Furthermore, MWCNT have significant effects on decreasing the friction coefficient and enhancing the wear resistance of the Fe-Ni coating.

Neutronic and mechanical evaluation of rare earth doped and undoped nitride-based coatings for accident tolerant fuels

As a part of the effort to develop accident-tolerant fuel (ATF) that would delay potential deleterious consequences of loss-of-coolant-accidents (LOCA), TiN and TiAlN coating application on nuclear fuel claddings were shown as a promising path to enhance corrosion resistance of nuclear fuel cladding. Recently, ytterbium doping was shown to contribute to improving TiAlN coating corrosion performance. However, overall cladding coating performance evaluation requires investigation of neutronic penalties and mechanical properties in addition to corrosion resistance. The current study is composed of two parts. First, the neutronic impact of adding monolithic TiN, monolithic TiAlN and 8-layer TiAlN/TiN coatings (with and without Yb dopants) to the exterior of conventional zirconium-alloy cladding was investigated. Second, an experimental investigation was performed through the deposition of select coating design architecture using cathodic arc physical vapor deposition process onto ZIRLO®1 sheets followed by mechanical testing to examine the adhesion and hardness of the coatings. Characterizations were performed using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron probe microanalysis (EPMA), Raman spectroscopy and X-ray diffraction (XRD). It is concluded that to minimize the neutronic penalties, a limitation on the concentration of Yb-dopant is necessary. Mechanical testing showed that hardness decreased with increasing Yb content. The adhesion of the TiAlN coatings was not affected by doping but was affected by the cathode composition.

CeO2 modified SiO2 acted as additive in electrodeposition of Zn-Ni alloy coating with enhanced corrosion resistance

Recently, rare earth oxide has attracted much attention because of its widely applications in petroleum, chemical engineering, metallurgy, ceramics etc. Among them, ceria has been considered as an important additive to improve metal's corrosion resistance. In this study, CeO2 modified SiO2 was prepared as additive in electrodeposition of Zn-Ni coating. The state of the as-prepared particles was characterized. The structure and wettability as well as the microhardness of coatings were tested. Moreover, the corrosion performance of coatings was analyzed in detail by means of potentiodynamic polarization technique and electrochemical impedance spectrum (EIS) in 3.5 wt % NaCl solution which used as corrosion medium. The results show that the particles disperse well among the coatings. The morphology of the coating presents a dense structure and keeps a highly preferred orientation. Meanwhile, the coating with CeO2 modified SiO2 exhibits much better corrosion resistance properties compared with that of both Zn-Ni and Zn-Ni-SiO2 coatings. The corrosion current density of the prepared coating was remarkably decreased with two and one orders of magnitude compared with those two CeO2-free coatings mentioned above, respectively. The introduction of CeO2 also significantly increases the coating's electrochemical impedance. The corrosion mechanism of the above three types of coating on low carbon steel were analyzed and discussed based on two different equivalent circuit models respectively.

High-performance hybrid coatings based on diamond-like carbon and copper for carbon steel protection

High performance double-layer coatings composed of copper (Cu) interlayer and the Cu/diamond-like carbon (DLC) composite top layer were prepared via magnetron sputtering for protection of carbon steel. The effect of Cu content in the composite layer on the internal stress, contact angle, mechanical, tribological, and corrosion performance of coatings was discussed. Raman spectroscopy confirmed formation of DLC phase. Double-layer Cu-rich coatings exhibited high degree of sp2 carbon clustering, but low diamond-like sp3 bonding. The internal stress of double layer Cu-(Cu/DLC composite) coatings was decreased with Cu content increase. The double-layer Cu-(Cu/DLC composite) thin films with low Cu content did not pose a significant effect on hardness and Young's modulus of the steel substrate, while increase of Cu content enhanced hardness of coating up to 28GPa. The contact angle of steel substrate showed an increase when coated with double-layer Cu-(Cu/DLC composite) thin film, but not that much at such inadequate Cu content. Inclusion of Cu interlayer improved to some extent corrosion properties, where increase of Cu content assisted in protection. Double-layer coatings with the highest performance were compared with single-layer Cu/DLC coating. Elimination of interlayer deteriorated mechanical properties, but increased electrochemical performance, signifying the importance of controlling Cu/DLC composition and Cu interlayer inclusion.

Synergistic Effect of Polypyrrole-Intercalated Graphene for Enhanced Corrosion Protection of Aqueous Coating in 3.5% NaCl Solution.

Dispersion of graphene in water and its incorporation into waterborne resin have been rarely researched and hardly achieved owing to its hydrophobicity. Furthermore, it has largely been reported that graphene with impermeability contributed to the improved anticorrosion property. Here, we show that highly concentrated graphene aqueous solution up to 5 mg/mL can be obtained by synthesizing hydrophilic polypyrrole (PPy) nanocolloids as intercalators and ultrasonic vibration. On the basis of π-π interaction between PPy and graphene, stacked graphene sheets are exfoliated to the thickness of three to five layers without increasing defects. The corrosion performance of coatings without and with PPy and graphene is obtained by potential and impedance measurements, Tafel curves, and fitted pore resistance by immersing in a 3.5 wt % NaCl solution. It turns out that composite coating with 0.5 wt % graphene additive exhibits superior anticorrosive ability. The mechanism of intercalated graphene-based coating is interpreted as the synergistic protection of impermeable graphene sheets and self-healing PPy and proved by the identification of corrosion products and the scanning vibrating electrode technique.