Research

13 pages, 4187 KiB

Open AccessArticle

Study on Friction and Wear Properties of Zr–Cu–Ni–Al Crystalline Powder Cladding and Amorphous Composite Powder Cladding by Laser

by Yugan Chen, Pingjun Tao, Weijian Zhang, Chaohan Zhang and Kunsen Zhu

Coatings 2021, 11(1), 103; https://doi.org/10.3390/coatings11010103 - 18 Jan 2021

Cited by 4 | Viewed by 1851

Abstract

In order to improve the friction and wear performance and surface hardness of AISI 1045 steel and expand its application range, this paper carried out the research on friction and wear performance and surface hardness of Zr₆₅Al_7.5Ni₁₀Cu [...] Read more.

In order to improve the friction and wear performance and surface hardness of AISI 1045 steel and expand its application range, this paper carried out the research on friction and wear performance and surface hardness of Zr₆₅Al_7.5Ni₁₀Cu_17.5 crystalline powder (CP) and amorphous powder (AP) after laser cladding on AISI 1045 steel surface. The results show that both CP and amorphous powder (AP) formed a cladding layer on the surface of AISI 1045 steel under laser irradiation. The thickness of the cladding layer is about 400 μm, and the thickness of the AP cladding layer is slightly larger than that of the CP cladding layer. The results show that there are many holes in the AP cladding layer, and holes can be observed at the junction with the matrix; while the CP cladding layer is well combined with the matrix and no holes are observed. The friction performance of CP cladding layer is better than that of AP cladding layer. In the wear marks of the AP cladding layer, there are bonding areas, while the wear marks of the CP cladding layer have a furrow-like morphology, and part of the matrix is exposed. The surface microhardness and average microhardness of AP cladding layer are 49% and 94% higher than that of CP cladding layer, respectively. Hardness modification has obvious advantages. The reasons for porosity, large friction coefficient and low stability of the friction experiment of the AP cladding layer are analyzed and discussed. The ideas and methods for improving the laser irradiation to achieve both high wear resistance and high strength of the AP cladding layer are proposed. Full article

(This article belongs to the Special Issue Coatings for Corrosion Mitigation)

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16 pages, 5152 KiB

Open AccessArticle

Reinforced Superhydrophobic Anti-Corrosion Epoxy Resin Coating by Fluorine–Silicon–Carbide Composites

by Zhicai Zhang, Nie Zhao, Fugang Qi, Biao Zhang, Bin Liao and Xiaoping Ouyang

Coatings 2020, 10(12), 1244; https://doi.org/10.3390/coatings10121244 - 17 Dec 2020

Cited by 25 | Viewed by 3874

Abstract

SiC was modified by fluorine-containing organic substance 1H,1H,2H,2H-trifluoro-noctyltriethoxysilane (FAS) to change its hydrophilicity from hydrophilic to superhydrophobic nanoparticles, and the optimum conditions for hydrophobicity were effectively explored. Then, different content of fluorine-modified SiC (F–SiC) nanoparticles were added to the epoxy resin (EP) matrix [...] Read more.

SiC was modified by fluorine-containing organic substance 1H,1H,2H,2H-trifluoro-noctyltriethoxysilane (FAS) to change its hydrophilicity from hydrophilic to superhydrophobic nanoparticles, and the optimum conditions for hydrophobicity were effectively explored. Then, different content of fluorine-modified SiC (F–SiC) nanoparticles were added to the epoxy resin (EP) matrix to prepare composite coating samples. The results showed that the surface of SiC was modified by FAS to show superhydrophobicity, and the dispersion in EP was significantly improved. After adding F–SiC, the hydrophobicity, wear resistance and corrosion resistance of the coating were significantly improved. In addition, the corrosion resistance of the composite coating containing different contents of F–SiC was analyzed through electrochemical and salt spray tests. The results showed that the corrosion resistance of the coating was the best when the addition amount was 3 wt %. In general, the composite coating with 3 wt % F–SiC had the best overall performance. Compared with the EP coating, the water contact angle of 3 wt % F–SiC/EP composite coating was increased by 62.9%, the friction coefficient was reduced by 73.5%, and the corrosion current was reduced by three orders of magnitude. This study provides a new idea for the development of ultra-wear-resistant and anti-fouling heavy-duty coatings. Full article

(This article belongs to the Special Issue Coatings for Corrosion Mitigation)

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11 pages, 14109 KiB

Open AccessEditor’s ChoiceArticle

Significant Improvement of Anticorrosion Properties of Zinc-Containing Coating Using Sodium Polystyrene Sulfonate Noncovalent Modified Graphene Dispersions

by Jiehui Li, Gang Niu, Wei Bai, Yanjie Ma, Qingren Xiong, Changyi Qin, Junjie Zhang, Ruihua An and Wei Ren

Coatings 2020, 10(12), 1150; https://doi.org/10.3390/coatings10121150 - 25 Nov 2020

Cited by 6 | Viewed by 2312

Abstract

High-quality graphene zinc-containing anticorrosive coatings are highly and urgently desirable for effective, economical anticorrosion of metals and alloys in industrial products. The realization of such coatings is, however, hindered by the dispersibility and compatibility of the graphene in them. This work reports a [...] Read more.

High-quality graphene zinc-containing anticorrosive coatings are highly and urgently desirable for effective, economical anticorrosion of metals and alloys in industrial products. The realization of such coatings is, however, hindered by the dispersibility and compatibility of the graphene in them. This work reports a novel direct modification of graphene using sodium polystyrene sulfonate (PSS) without reduction of graphene oxide, leading to homogeneous dispersion of graphene in water. The agglomeration of graphene is prevented thanks to the formation of π−π interaction between PSS and graphene sheets. Such graphene dispersion can effectively improve the anticorrosion performance of the zinc-containing epoxy coatings. With the addition of graphene modified by PSS into the 20% zinc-containing epoxy coating (graphene is 0.05% by weight of the coating), its anticorrosion properties revealed by both electrochemical characterization and the neutral salt spray tolerance analysis are rather close to those of 60% zinc-containing epoxy coating. These results demonstrate that direct PSS modification is an effective method for graphene dispersion and thus open a pathway to achieve graphene zinc-containing anticorrosive coatings with high performance. Full article

(This article belongs to the Special Issue Coatings for Corrosion Mitigation)

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20 pages, 4543 KiB

Open AccessArticle

Thiocarbohydrazones Based on Adamantane and Ferrocene as Efficient Corrosion Inhibitors for Hydrochloric Acid Pickling of C-Steel

by Abdelwahed R. Sayed and Hany M. Abd El-Lateef

Coatings 2020, 10(11), 1068; https://doi.org/10.3390/coatings10111068 - 06 Nov 2020

Cited by 21 | Viewed by 1934

Abstract

N′-(adamantan-2-ylidene)hydrazinecarbothiohydrazide and 2-(ferrocenyl-1-ylidene) hydrazinecarbothiohydrazide are used in coordination and organometallic complexes. The important idea of the research in this paper is the principal to prepare thiocarbohydrazones from the reaction of 2-acetylferrocene (Fe-Th) or 2-adamantanone (Ad-Th) with carbonothioic dihydrazide. The materials were elucidated by [...] Read more.

N′-(adamantan-2-ylidene)hydrazinecarbothiohydrazide and 2-(ferrocenyl-1-ylidene) hydrazinecarbothiohydrazide are used in coordination and organometallic complexes. The important idea of the research in this paper is the principal to prepare thiocarbohydrazones from the reaction of 2-acetylferrocene (Fe-Th) or 2-adamantanone (Ad-Th) with carbonothioic dihydrazide. The materials were elucidated by elemental analysis and spectral data. The as-prepared compounds were applied as effective corrosion inhibitors for HCl pickling of C-steel. Detailed investigations on electrochemical (open circuit potential (OCP) vs. time, potentiodynamic polarization (PDP), and impedance spectroscopy (EIS)) techniques and surface morphology studies are introduced in this work. Results indicated that Fe-Th could deliver greater inhibition performance than Ad-Th, and the highest protection capacity values of 93.6% (Ad-Th) and 97.9% (Fe-Th) were accomplished at 200 ppm. The adsorption of Ad-Th or Fe-Th additives followed the Langmuir isotherm with both the chemical and the physical adsorption with chemisorption predominance. EIS measurements supported a betterment in the capacitive behavior with the corrosion inhibitors. The inhibitors exhibited a mixed-type behavior as observed from the PDP studies. Field emission scanning electron microscopy (FESEM) and Fourier-transform infrared spectroscopy (FTIR) studies emphasize the occurrence of a protective layer of the as-synthesized organic inhibitors on the C-steel interface. Theoretical studies (density functional theory (DFT) calculations and Monte Carlo (MC) simulations) provide appropriate support for the experimental findings. The existing report provides very significant consequences in formulating and designing novel thiocarbohydrazone inhibitors with high protection efficacy. Full article

(This article belongs to the Special Issue Coatings for Corrosion Mitigation)

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11 pages, 3672 KiB

Open AccessArticle

Microstructure and Corrosion Behavior of Cold-Sprayed Zn-Al Composite Coating

by Zhipo Zhao, Junrong Tang, Naeem ul Haq Tariq, Jiqiang Wang, Xinyu Cui and Tianying Xiong

Coatings 2020, 10(10), 931; https://doi.org/10.3390/coatings10100931 - 29 Sep 2020

Cited by 18 | Viewed by 2891

Abstract

A Zn–Al composite coating was successfully deposited on Q235 steel by cold spray technology for the corrosion protection in the marine atmosphere. The microstructure and corrosion behavior of the prepared coating was studied byScanning Electron Microscope (SEM), X-ray Diffraction (XRD), salt spray test [...] Read more.

A Zn–Al composite coating was successfully deposited on Q235 steel by cold spray technology for the corrosion protection in the marine atmosphere. The microstructure and corrosion behavior of the prepared coating was studied byScanning Electron Microscope (SEM), X-ray Diffraction (XRD), salt spray test and electrochemical experiments. A 2400-h neutral salt spray corrosion test (with a corrosion medium of 3.5% sodium chloride solution) showed that the prepared cold-sprayed Zn-Al composite coating has excellent anti-corrosion properties. Based on the microstructure evolution and corrosion products analysis, droplets’ flow-driven ‘synergistic corrosion effect’ was proposed to explain the co-corrosion behavior of Zn and Al particles in the composite coating. Full article

(This article belongs to the Special Issue Coatings for Corrosion Mitigation)

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4248 KiB

Open AccessArticle

Electrochemical Behavior of Bilayer Thermal-Spray Coatings in Low-Temperature Corrosion Protection

by Esmaeil Sadeghimeresht and Nicolaie Markocsan

Coatings 2017, 7(10), 162; https://doi.org/10.3390/coatings7100162 - 30 Sep 2017

Cited by 14 | Viewed by 6120

Abstract

Cr₃C₂-NiCr coatings are greatly used to protect critical components in corrosive environments and to extend their lifetime and/or improve functional performance. However, the pores formed during spraying restrict the coating’s applicability area for many corrosion protection applications. To overcome [...] Read more.

Cr₃C₂-NiCr coatings are greatly used to protect critical components in corrosive environments and to extend their lifetime and/or improve functional performance. However, the pores formed during spraying restrict the coating’s applicability area for many corrosion protection applications. To overcome this technical challenge, bilayer coatings have been developed, in which an additional layer (the so-called “intermediate layer”) is deposited on the substrate before spraying the Cr₃C₂-NiCr coating (the so-called “top layer”). The corrosion behavior of the bilayer coating depends on the composition and microstructure of each layer. In the present work, different single-layer coatings (i.e., Cr₃C₂-NiCr, Fe- and Ni-based coatings) were initially sprayed by a high-velocity air fuel (HVAF) process. Microstructure analysis, as well as electrochemical tests, for example, open-circuit potential (OCP) and polarization tests, were performed. The potential difference (ΔE) had a great influence on galvanic corrosion between the top and intermediate layers, and thus, the coatings were ranked based on the OCP values (from high to low) as follows: NiCoCrAlY > NiCr > Cr₃C₂-NiCr > NiAl > Fe-based coatings (alloyed with Cr) > pure Ni. The Ni-based coatings were chosen to be further used as intermediate layers with the Cr₃C₂-NiCr top layer due to their capabilities to show high OCP. The corrosion resistance (R_p) of the bilayer coatings was ranked (from high to low) as follows: NiCoCrAlY/Cr₃C₂-NiCr > NiCr/Cr₃C₂-NiCr > NiAl/Cr₃C₂-NiCr > Ni/Cr₃C₂-NiCr. It was shown that splat boundaries and interconnected pores are detrimental for corrosion resistance, however, a sufficient reservoir of protective scale-forming elements (such as Cr or/and Al) in the intermediate layer can significantly improve the corrosion resistance. Full article

(This article belongs to the Special Issue Coatings for Corrosion Mitigation)

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11434 KiB

Open AccessArticle

Biodegradable Mg/HA/TiO₂ Nanocomposites Coated with MgO and Si/MgO for Orthopedic Applications: A Study on the Corrosion, Surface Characterization, and Biocompatability

by Shahrouz Zamani Khalajabadi, Aminudin Bin Haji Abu, Norhayati Ahmad, Mohammed Rafiq Abdul Kadir, Ahmad Fauzi Ismail, Rozita Nasiri, Waseem Haider and Norizah Bt Hj Redzuan

Coatings 2017, 7(10), 154; https://doi.org/10.3390/coatings7100154 - 26 Sep 2017

Cited by 17 | Viewed by 6539

Abstract

In the field of orthopedics, magnesium (Mg) and magnesium-based composites as biodegradable materials have attracted fundamental research. However, the medical applications of magnesium implants have been restricted owing to their poor corrosion resistance, especially in the physiological environment. To improve the corrosion resistance [...] Read more.

In the field of orthopedics, magnesium (Mg) and magnesium-based composites as biodegradable materials have attracted fundamental research. However, the medical applications of magnesium implants have been restricted owing to their poor corrosion resistance, especially in the physiological environment. To improve the corrosion resistance of Mg/HA/TiO₂ nanocomposites, monolayer MgO and double-layer Si/MgO coatings were fabricated layer-by-layer on the surface of a nanocomposite using a powder metallurgy route. Then, coating thickness, surface morphology, and chemical composition were determined, and the corrosion behavior of the uncoated and coated samples was evaluated. Field-emission scanning electron microscopy (FE-SEM) micrographs show that an inner MgO layer with a porous microstructure and thickness of around 34 μm is generated on the Mg/HA/TiO₂ nanocomposite substrate, and that the outer Si layer thickness is obtained at around 23 μm for the double-layered coated sample. Electrochemical corrosion tests and immersion corrosion tests were carried out on the uncoated and coated samples and the Si/MgO-coated nanocomposite showed significantly improved corrosion resistance compared with uncoated Mg/HA/TiO₂ in simulated body fluid (SBF). Corrosion products comprising Mg(OH)₂, HA, Ca₃(PO₄)₂, and amorphous CaP components were precipitated on the immersed samples. Improved cytocompatibility was observed with coating as the cell viability ranged from 73% in uncoated to 88% for Si/MgO-coated Mg/HA/TiO₂ nanocomposite after nine days of incubation. Full article

(This article belongs to the Special Issue Coatings for Corrosion Mitigation)

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10060 KiB

Open AccessArticle

Nanoscale Characterization of Glass Flake Filled Vinyl Ester Anti-Corrosion Coatings

by Salim Barbhuiya and Mohammad Ikbal Choudhury

Coatings 2017, 7(8), 116; https://doi.org/10.3390/coatings7080116 - 04 Aug 2017

Cited by 10 | Viewed by 5839

Abstract

Vinyl ester is a thermoset matrix resin that is widely used in the coating industry. The presence of glass flakes further enhances the anti-corrosion performance of this coating. This paper reports the nanoscaled characterization of glass flake filled vinyl ester anti-corrosion coatings on [...] Read more.

Vinyl ester is a thermoset matrix resin that is widely used in the coating industry. The presence of glass flakes further enhances the anti-corrosion performance of this coating. This paper reports the nanoscaled characterization of glass flake filled vinyl ester anti-corrosion coatings on mild steel. Bond strength properties of one uncoated and four coated samples with different thicknesses (300, 600, 900 and 1200 μm) were studied using nanoscratch technique and ASTM Standard Test. It was found that the bond strength of coating with thickness 900 μm was the highest. The frequency distributions of elastic modulus on coating with 900 μm thickness determined using nanoindentation indicated that only 20–25% of the coating is composed of glass flakes and the balance is vinyl ester matrix. The critical depth at which the material is subject to failure due to external load and abrasion, was found to be around 100 nm. Full article

(This article belongs to the Special Issue Coatings for Corrosion Mitigation)

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4585 KiB

Open AccessArticle

Investigation on the Cathodic Protection Effect of Low Pressure Cold Sprayed AlZn Coating in Seawater via Numerical Simulation

by Guosheng Huang, Xiaodan Lou, Hongren Wang, Xiangbo Li and Lukuo Xing

Coatings 2017, 7(7), 93; https://doi.org/10.3390/coatings7070093 - 04 Jul 2017

Cited by 9 | Viewed by 6143

Abstract

Cold spray can deposit a composite coating simply by spraying mechanically-mixed Al and Zn powders, while no quantitative data has been reported on the anti-corrosion performance of different composite cold-sprayed coatings. In the present work, the finite element method was used to estimate [...] Read more.

Cold spray can deposit a composite coating simply by spraying mechanically-mixed Al and Zn powders, while no quantitative data has been reported on the anti-corrosion performance of different composite cold-sprayed coatings. In the present work, the finite element method was used to estimate the cathodic protection effect by simulating the potential distribution on a damaged cold-sprayed AlZn coating on Q235 steel. The results indicate that AlZn coating can only provide a limiting cathodic protection for substrate, because it can only polarize a very narrow zone negative to −0.78 V (vs. SCE, saturated calomel electrode). The remaining area of the steel substrate still has a very high residual corrosion rate. Computational methods can be used to predict the corrosion rate of AlZn coating, and the simulation results were validated by the results of a weight loss experiment. Full article

(This article belongs to the Special Issue Coatings for Corrosion Mitigation)

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4962 KiB

Open AccessArticle

Silica-Based Sol-Gel Coating on Magnesium Alloy with Green Inhibitors

by Vinod Upadhyay, Zachary Bergseth, Brett Kelly and Dante Battocchi

Coatings 2017, 7(7), 86; https://doi.org/10.3390/coatings7070086 - 22 Jun 2017

Cited by 19 | Viewed by 6139

Abstract

In this work, the performances of several natural organic inhibitors were investigated in a sol-gel system (applied on the magnesium alloy Mg AZ31B substrate). The inhibitors were quinaldic acid (QDA), betaine (BET), dopamine hydrochloride (DOP), and diazolidinyl urea (DZU). Thin, uniform, and defect-free [...] Read more.

In this work, the performances of several natural organic inhibitors were investigated in a sol-gel system (applied on the magnesium alloy Mg AZ31B substrate). The inhibitors were quinaldic acid (QDA), betaine (BET), dopamine hydrochloride (DOP), and diazolidinyl urea (DZU). Thin, uniform, and defect-free sol-gel coatings were prepared with and without organic inhibitors, and applied on the Mg AZ31B substrate. SEM and EDX were performed to analyze the coating surface properties, the adhesion to the substrate, and the thickness. Electrochemical measurements, including electrochemical impedance spectroscopy (EIS) and anodic potentiodynamic polarization scan (PDS), were performed on the coated samples to characterize the coatings’ protective properties. Also, hydrogen evolution measurement—an easy method to measure magnesium corrosion—was performed in order to characterize the efficiency of coating protection on the magnesium substrate. Moreover, scanning vibrating electrode technique (SVET) measurements were performed to examine the efficiency of the coatings loaded with inhibitors in preventing and containing corrosion events in defect areas. From the testing results it was observed that the formulated sol-gel coatings provided a good barrier to the substrate, affording some protection even without the presence of inhibitors. Finally, when the inhibitors’ performances were compared, the QDA-doped sol-gel was able to contain the corrosion event at the defect. Full article

(This article belongs to the Special Issue Coatings for Corrosion Mitigation)

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6121 KiB

Open AccessArticle

The Effect of Temperature and Local pH on Calcareous Deposit Formation in Damaged Thermal Spray Aluminum (TSA) Coatings and Its Implication on Corrosion Mitigation of Offshore Steel Structures

by Nataly Ce and Shiladitya Paul

Coatings 2017, 7(4), 52; https://doi.org/10.3390/coatings7040052 - 11 Apr 2017

Cited by 17 | Viewed by 5964

Abstract

This paper is based on experimental data and provides better understanding of the mechanism of calcareous deposit formation on cathodically polarized steel surfaces exposed to synthetic seawater at 30 °C and 60 °C. The study comprises measurement of the interfacial pH of thermally [...] Read more.

This paper is based on experimental data and provides better understanding of the mechanism of calcareous deposit formation on cathodically polarized steel surfaces exposed to synthetic seawater at 30 °C and 60 °C. The study comprises measurement of the interfacial pH of thermally sprayed aluminum (TSA) coated steel samples with and without a holiday (exposing 20% of the surface area). Tests were conducted at the corrosion potential for up to 350 h. It was experimentally determined that the local pH adjacent to the steel surface in the holiday region reached a maximum of 10.19 and 9.54 at 30 °C and 60 °C, respectively, before stabilizing at about 8.8 and 7.9 at the two temperatures. The interfacial pH on the TSA coating at 30 °C was initially 7.74 dropping to 4.76 in 220 h, while at 60 °C it increased from pH 6.41 to the range pH 7.0–8.5. The interfacial pH governed the deposition of brucite and aragonite from seawater on the steel surface cathodically polarized by the TSA. This mechanism is likely to affect the performance of TSA-coated offshore steel structures, especially when damaged in service. Full article

(This article belongs to the Special Issue Coatings for Corrosion Mitigation)

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2170 KiB

Open AccessArticle

High-Temperature Corrosion of AlCrSiN Film in Ar-1%SO₂ Gas

by Poonam Yadav, Dong Bok Lee, Yue Lin, Shihong Zhang and Sik Chol Kwon

Coatings 2017, 7(3), 44; https://doi.org/10.3390/coatings7030044 - 13 Mar 2017

Cited by 3 | Viewed by 4719

Abstract

AlCrSiN film with a composition of 29.1Al-17.1Cr-2.1Si-51.7N in at. % was deposited on a steel substrate by cathodic arc ion plating at a thickness of 1.8 μm. It consisted of nanocrystalline hcp-AlN and fcc-CrN, where a small amount of Si was [...] Read more.

AlCrSiN film with a composition of 29.1Al-17.1Cr-2.1Si-51.7N in at. % was deposited on a steel substrate by cathodic arc ion plating at a thickness of 1.8 μm. It consisted of nanocrystalline hcp-AlN and fcc-CrN, where a small amount of Si was dissolved. Corrosion tests were carried out at 800 °C for 5–200 h in Ar-1%SO₂ gas. The major corrosion reaction was oxidation owing to the high oxygen affinity of Al and Cr in the film. The formed oxide scale consisted primarily of (Al,Cr)₂O₃, within which Fe, Si, and S were dissolved. Even after corrosion for 200 h, the thickness of the scale was about 0.7–1.2 μm, indicating that the film had good corrosion resistance in the SO₂-containing atmosphere. Full article

(This article belongs to the Special Issue Coatings for Corrosion Mitigation)

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13691 KiB

Open AccessArticle

Pitted Corrosion Detection of Thermal Sprayed Metallic Coatings Using Fiber Bragg Grating Sensors

by Fodan Deng, Ying Huang, Fardad Azarmi and Yechun Wang

Coatings 2017, 7(3), 35; https://doi.org/10.3390/coatings7030035 - 24 Feb 2017

Cited by 18 | Viewed by 6922

Abstract

Metallic coatings using thermal spraying techniques are widely applied to structural steels to protect infrastructure against corrosion and improve durability of the associated structures for longer service life. The thermal sprayed metallic coatings consisting of various metals, although have higher corrosion resistance, will [...] Read more.

Metallic coatings using thermal spraying techniques are widely applied to structural steels to protect infrastructure against corrosion and improve durability of the associated structures for longer service life. The thermal sprayed metallic coatings consisting of various metals, although have higher corrosion resistance, will still corrode in a long run and may also subject to corrosion induced damages such as cracks. Corrosion and the induced damages on the metallic coatings will reduce the effectiveness of the coatings for protection of the structures. Timely repair on these damaged metallic coatings will significantly improve the reliability of protected structures again deterioration. In this paper, an inline detection system for corrosion and crack detection was developed using fiber Bragg (FBG) grating sensors. Experimental results from laboratory accelerated corrosion tests showed that the developed sensing system can quantitatively detect corrosion rate of the coating, corrosion propagations, and cracks initialized in the metallic coating in real time. The developed system can be used for real-time corrosion detection of coated metal structures in field. Full article

(This article belongs to the Special Issue Coatings for Corrosion Mitigation)

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1558 KiB

Open AccessArticle

Effects of Rare Earth Elements on Properties of Ni-Base Superalloy Powders and Coatings

by Chunlian Hu and Shanglin Hou

Coatings 2017, 7(2), 30; https://doi.org/10.3390/coatings7020030 - 16 Feb 2017

Cited by 9 | Viewed by 5357

Abstract

NiCrMoY alloy powders were prepared using inert gas atomization by incorporation of rare earth elements, such as Mo, Nb, and Y into Ni60A powders, the coatings were sprayed by oxy-acetylene flame spray and then remelted with high-frequency induction. The morphologies, hollow particle ratio, [...] Read more.

NiCrMoY alloy powders were prepared using inert gas atomization by incorporation of rare earth elements, such as Mo, Nb, and Y into Ni60A powders, the coatings were sprayed by oxy-acetylene flame spray and then remelted with high-frequency induction. The morphologies, hollow particle ratio, particle-size distribution, apparent density, flowability, and the oxygen content of the NiCrMoY alloy powders were investigated, and the microstructure and hardness of the coatings were evaluated by optical microscopy (OM). Due to incorporation of the rare earth elements of Mo, Nb, or Y, the majority of the NiCrMoY alloy particles are near-spherical, the minority of which have small satellites, the surface of the particles is smoother and hollow particles are fewer, the particles exhibit larger apparent density and lower flowability than those of particles without incorporation, i.e., Ni60A powders, and particle-size distribution exhibits a single peak and fits normal distribution. The microstructure of the NiCrMoY alloy coatings exhibits finer structure and Rockwell hardness HRC of 60–63 in which the bulk- and needle-like hard phases are formed. Full article

(This article belongs to the Special Issue Coatings for Corrosion Mitigation)

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17115 KiB

Open AccessArticle

Investigation of the Corrosion Behavior of Electroless Ni-P Coating in Flue Gas Condensate

by Hejie Yang, Yimin Gao and Weichao Qin

Coatings 2017, 7(1), 16; https://doi.org/10.3390/coatings7010016 - 19 Jan 2017

Cited by 9 | Viewed by 5940

Abstract

The corrosion behavior of Ni-P coating deposited on 3003 aluminum alloy in flue gas condensate was investigated by electrochemical approaches. The results indicated that nitrite acted as a corrosion inhibitor. The inhibiting effect of nitrite was reduced in solutions containing sulfate or nitrate. [...] Read more.

The corrosion behavior of Ni-P coating deposited on 3003 aluminum alloy in flue gas condensate was investigated by electrochemical approaches. The results indicated that nitrite acted as a corrosion inhibitor. The inhibiting effect of nitrite was reduced in solutions containing sulfate or nitrate. Chloride and sulfate accelerated the corrosion of Ni-P coatings greatly. This can provide important information for the researchers to develop special Ni-P coatings with high corrosion resistance in the flue gas condensate. Full article

(This article belongs to the Special Issue Coatings for Corrosion Mitigation)

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