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3 pages, 170 KiB

Open AccessEditorial

Special Issue: Advanced Coatings for Corrosion Protection

by Wolfram Fürbeth

Materials 2020, 13(15), 3401; https://doi.org/10.3390/ma13153401 - 1 Aug 2020

Cited by 8 | Viewed by 3002

Abstract

Corrosion is an important issue in many industrial fields. Among others, coatings are by far the most important technology for corrosion protection of metallic surfaces. The special issue “Advanced Coatings for Corrosion Protection” has been launched as a means to present recent developments [...] Read more.

Corrosion is an important issue in many industrial fields. Among others, coatings are by far the most important technology for corrosion protection of metallic surfaces. The special issue “Advanced Coatings for Corrosion Protection” has been launched as a means to present recent developments on any type of advanced coatings for corrosion protection. Fifteen contributions have been collected on metallic, inorganic, polymeric and nanoparticle enhanced coatings providing corrosion protection as well as partly other functionalities. Full article

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

Research

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14 pages, 1745 KiB

Open AccessArticle

Alternative to Nitric Acid Passivation of 15-5 and 17-4PH Stainless Steel Using Electrochemical Techniques

by María Lara-Banda, Citlalli Gaona-Tiburcio, Patricia Zambrano-Robledo, Marisol Delgado-E, José A. Cabral-Miramontes, Demetrio Nieves-Mendoza, Erick Maldonado-Bandala, Francisco Estupiñan-López, José G. Chacón-Nava and Facundo Almeraya-Calderón

Materials 2020, 13(12), 2836; https://doi.org/10.3390/ma13122836 - 24 Jun 2020

Cited by 40 | Viewed by 5260 | Correction

Abstract

Increasingly stringent environmental regulations in different sectors of industry, especially the aeronautical sector, suggest the need for more investigations regarding the effect of environmentally friendly corrosion protective processes. Passivation is a finishing process that makes stainless steels more rust resistant, removing free iron [...] Read more.

Increasingly stringent environmental regulations in different sectors of industry, especially the aeronautical sector, suggest the need for more investigations regarding the effect of environmentally friendly corrosion protective processes. Passivation is a finishing process that makes stainless steels more rust resistant, removing free iron from the steel surface resulting from machining operations. This results in the formation of a protective oxide layer that is less likely to react with the environment and cause corrosion. The most commonly used passivating agent is nitric acid. However, it is know that high levels of toxicity can be generated by using this agent. In this work, a study has been carried out into the electrochemical behavior of 15-5PH (precipitation hardening) and 17-4PH stainless steels passivated with (a) citric and (b) nitric acid solutions for 60 and 90 min at 49 °C, and subsequently exposed to an environment with chlorides. Two electrochemical techniques were used: electrochemical noise (EN) and potentiodynamic polarization curves (PPC) according to ASTM G199-09 and ASTM G5-13, respectively. The results obtained indicated that, for both types of steel, the passive layer formed in citric acid as passivating solution had very similar characteristics to that formed with nitric acid. Furthermore, after exposure to the chloride-containing solution and according with the localization index (LI) values obtained, the stainless steels passivated in citric acid showed a mixed type of corrosion, whereas the steels passivated in nitric acid showed localized corrosion. Overall, the results of the

R_{n}

values derived show very low and similar corrosion rates for the stainless steels passivated with both citric and nitric acid solutions. Full article

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

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11 pages, 5248 KiB

Open AccessArticle

Enhanced Erosion–Corrosion Resistance of Tungsten by Carburizing Using Spark Plasma Sintering Technique

by Yan Jiang, Junfeng Yang, Zhuoming Xie and Qianfeng Fang

Materials 2020, 13(12), 2719; https://doi.org/10.3390/ma13122719 - 15 Jun 2020

Cited by 3 | Viewed by 2709

Abstract

The biggest obstacle for the application of tungsten as the target materials in the spallation neutron source is its serious corrosion in the coolant of flowing water. For this reason, W–Cr–C clad tungsten was developed by tungsten carburizing in a spark plasma sintering [...] Read more.

The biggest obstacle for the application of tungsten as the target materials in the spallation neutron source is its serious corrosion in the coolant of flowing water. For this reason, W–Cr–C clad tungsten was developed by tungsten carburizing in a spark plasma sintering device, with superior corrosion resistance in the static immersion and electrochemical corrosion test. This work focused on its erosion and corrosion performance in a flowing water system, based upon test parameters simulated under the service conditions. W–Cr–C clad tungsten showed superior corrosion resistance to that of bare tungsten due to the corrosion form changing from the intergranular corrosion of bare tungsten to pitting corrosion of W–Cr–C coating. The corrosion rate of tungsten was as high as tenfold that of the coated sample at 20 °C, and at most fourfold at 60 °C after testing for 360 h. Effects of water velocity and temperature on pitting and intergranular corrosion were investigated in detail and their corresponding corrosion mechanisms were analyzed and discussed. Full article

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

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9 pages, 3309 KiB

Open AccessArticle

Investigations of the Deuterium Permeability of As-Deposited and Oxidized Ti₂AlN Coatings

by Lukas Gröner, Lukas Mengis, Mathias Galetz, Lutz Kirste, Philipp Daum, Marco Wirth, Frank Meyer, Alexander Fromm, Bernhard Blug and Frank Burmeister

Materials 2020, 13(9), 2085; https://doi.org/10.3390/ma13092085 - 1 May 2020

Cited by 12 | Viewed by 4315

Abstract

Aluminum containing M_n+1AX_n (MAX) phase materials have attracted increasing attention due to their corrosion resistance, a pronounced self-healing effect and promising diffusion barrier properties for hydrogen. We synthesized Ti₂AlN coatings on ferritic steel substrates by physical vapor deposition [...] Read more.

Aluminum containing M_n+1AX_n (MAX) phase materials have attracted increasing attention due to their corrosion resistance, a pronounced self-healing effect and promising diffusion barrier properties for hydrogen. We synthesized Ti₂AlN coatings on ferritic steel substrates by physical vapor deposition of alternating Ti- and AlN-layers followed by thermal annealing. The microstructure developed a {0001}-texture with platelet-like shaped grains. To investigate the oxidation behavior, the samples were exposed to a temperature of 700 °C in a muffle furnace. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) depth profiles revealed the formation of oxide scales, which consisted mainly of dense and stable α-Al₂O₃. The oxide layer thickness increased with a time dependency of ~t^1/4. Electron probe micro analysis (EPMA) scans revealed a diffusion of Al from the coating into the substrate. Steel membranes with as-deposited Ti₂AlN and partially oxidized Ti₂AlN coatings were used for permeation tests. The permeation of deuterium from the gas phase was measured in an ultra-high vacuum (UHV) permeation cell by mass spectrometry at temperatures of 30–400 °C. We obtained a permeation reduction factor (PRF) of 45 for a pure Ti₂AlN coating and a PRF of ~3700 for the oxidized sample. Thus, protective coatings, which prevent hydrogen-induced corrosion, can be achieved by the proper design of Ti₂AlN coatings with suitable oxide scale thicknesses. Full article

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

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18 pages, 7208 KiB

Open AccessArticle

The Effect of Laser Power on the Properties of M₃B₂-Type Boride-Based Cermet Coatings Prepared by Laser Cladding Synthesis

by Zhaowei Hu, Wenge Li and Yuantao Zhao

Materials 2020, 13(8), 1867; https://doi.org/10.3390/ma13081867 - 16 Apr 2020

Cited by 12 | Viewed by 2574

Abstract

Boride-based cermet can serve as a good protective coating for low-corrosion and wear-resistant materials, such as carbon steels, due to their mechanical and chemical properties. In this study, M₃B₂ (M: Mo, Ni, Fe, and Cr) boride-based cermet coatings were fabricated [...] Read more.

Boride-based cermet can serve as a good protective coating for low-corrosion and wear-resistant materials, such as carbon steels, due to their mechanical and chemical properties. In this study, M₃B₂ (M: Mo, Ni, Fe, and Cr) boride-based cermet coatings were fabricated on Q235 steel with mixed powders of Mo, B, Ni60, and Cr by laser cladding synthesis, and the effects of laser power on the properties of the cermet layer were investigated. Three laser powers (2200, 2500, and 2800 W) were used at the same scanning speed. The X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) analysis confirmed that all the coatings were composed of M₃B₂-type borides and {Fe, Ni} alloys. The micro-hardness, corrosion, and frictional experiments showed that the cermet coatings enhanced the corresponding performances of the Q235 steels at the three laser powers. However, the micro-hardness of the coatings decreased as the power increased, and the maximum micro-hardness value was 1166.3 HV (Vickers Hardness). The results of the corrosion and frictional experiments showed that the best performance was obtained at a laser power of 2500 W, followed by 2800 and 2200 W. Full article

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

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15 pages, 2200 KiB

Open AccessArticle

Material Analysis and Molecular Dynamics Simulation for Cavitation Erosion and Corrosion Suppression in Water Hydraulic Valves

by Masoud Kamoleka Mlela, He Xu, Feng Sun, Haihang Wang and Gabriel Donald Madenge

Materials 2020, 13(2), 453; https://doi.org/10.3390/ma13020453 - 17 Jan 2020

Cited by 12 | Viewed by 3484

Abstract

In the milestone of straggling to make water hydraulics more advantageous, the choice of coating polymer for water hydraulics valves plays an essential role in alleviating the impact of cavitation erosion and corrosion, and this is a critical task for designers. Fulfilling the [...] Read more.

In the milestone of straggling to make water hydraulics more advantageous, the choice of coating polymer for water hydraulics valves plays an essential role in alleviating the impact of cavitation erosion and corrosion, and this is a critical task for designers. Fulfilling the appropriate selection, we conflicted properties that are vital for erosion and corrosion inhibitors, as well as the tribology in the sense of coefficient of friction. This article aimed to choose the best alternative polymer for coating on the selected substrate, that is, Cr₂O₃, Al₂O₃, T_i2O₃. By applying PROMETHEE (Preference Ranking Organization Method for Enrichment Evaluations), the best polymer obtained with an analyzed performance attribute is Polytetrafluoroethylene (PTFE) that comes up with higher outranking (0.5932052). A Molecular Dynamics (MD) simulation was conducted to identify the stronger bonding with the regards of the better cleave plane between Polytetrafluoroethylene (PTFE) and the selected substrate. Polytetrafluoroethylene (PTFE)/Al₂O₃ cleaved in (010) plane was observed to be the strongest bond in terms of binding energy (3188 kJ/mol) suitable for further studies. Full article

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

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11 pages, 5049 KiB

Open AccessArticle

Influence of Micro-Arc Oxidation Coatings on Stress Corrosion of AlMg6 Alloy

by Lesław Kyzioł and Aleksandr Komarov

Materials 2020, 13(2), 356; https://doi.org/10.3390/ma13020356 - 12 Jan 2020

Cited by 7 | Viewed by 2602

Abstract

This paper shows results of a study on the corrosion behavior of micro-arc oxidation (MAO) coatings sampled from the AlMg6 alloy. The alloy was simultaneously subjected to a corrosive environment and static tensile stress. For comparative purposes, the tests were run for both [...] Read more.

This paper shows results of a study on the corrosion behavior of micro-arc oxidation (MAO) coatings sampled from the AlMg6 alloy. The alloy was simultaneously subjected to a corrosive environment and static tensile stress. For comparative purposes, the tests were run for both coated samples and samples without coatings. The research was conducted at a properly prepared stand; the samples were placed in a glass container filled with 3.5% NaCl aqueous solution and stretched. Two levels of tensile stress were accepted for the samples: σ₁ = 0.8R_0.2 σ₂ = R_0.2, and the tests were run for two time intervals: t₁ = 480 h and t₂ = 1000 h. Prolonged stress corrosion tests (lasting up to 1000 h) showed that the samples covered with ceramic coatings demonstrated significantly higher corrosion resistance than the samples without the coatings. Protective properties of the coating could be explained by its structure. Surface pores were insignificant, and their depth was very limited. The porosity level of the main coating layer was 1%. Such a structure of coating and its phase composition provided high protective properties. Full article

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

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11 pages, 7251 KiB

Open AccessArticle

Preparation and Corrosion Behavior in Marine Environment of MAO Coatings on Magnesium Alloy

by Yuhong Yao, Wei Yang, Dongjie Liu, Wei Gao and Jian Chen

Materials 2020, 13(2), 345; https://doi.org/10.3390/ma13020345 - 12 Jan 2020

Cited by 15 | Viewed by 3178

Abstract

To improve the corrosion performance of magnesium alloys in the marine environment, the MAO, MAO–Cu₂CO₃(OH)₂·H₂O and MAO–Cu₂P₂O₇ ceramic coatings were deposited on AZ91D magnesium alloys in basic electrolyte and the [...] Read more.

To improve the corrosion performance of magnesium alloys in the marine environment, the MAO, MAO–Cu₂CO₃(OH)₂·H₂O and MAO–Cu₂P₂O₇ ceramic coatings were deposited on AZ91D magnesium alloys in basic electrolyte and the discoloration mechanism of the Cu-doped MAO coatings and the corrosion behavior of the three MAO coatings in the artificial seawater solution were investigated by SEM, EDS and XPS. The results indicated that the formation and discoloration mechanism of the brown MAO ceramic coatings were attributable to the formation of Cu₂O in the coatings. Though the three MAO coatings had a certain protective effect against the corrosion of AZ91D substrate in the artificial seawater, the distinctive stratification phenomenon was found on the MAO–Cu₂P₂O₇ coated sample and the corrosion model of the MAO–Cu₂P₂O₇ coatings in the immersion experiment was established. Therefore, the brown Cu-doped MAO coatings were speculated to significantly reduce the risk of the magnesium parts in marine environments. Full article

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

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15 pages, 7024 KiB

Open AccessArticle

Investigations on Aging Behavior and Mechanism of Polyurea Coating in Marine Atmosphere

by Kaiyuan Che, Ping Lyu, Fei Wan and Mingliang Ma

Materials 2019, 12(21), 3636; https://doi.org/10.3390/ma12213636 - 5 Nov 2019

Cited by 43 | Viewed by 5600

Abstract

In this investigation, the aging behaviors of polyurea coating exposed to marine atmosphere for 150 days were studied and the mechanism was analyzed. The influences on surface and mechanical properties, surface morphology, thermal stability behavior, as well as chemical changes evolution of the [...] Read more.

In this investigation, the aging behaviors of polyurea coating exposed to marine atmosphere for 150 days were studied and the mechanism was analyzed. The influences on surface and mechanical properties, surface morphology, thermal stability behavior, as well as chemical changes evolution of the coating were investigated. By attenuated total reflectance fourier transform infrared spectroscopy (ATR–FTIR) and X-ray photoelectron spectroscopy (XPS), changes in the chemical properties of polyurea coatings before (PCB) and after 150 d (PCA) of aging were analyzed, and emphasis was given to the effect of aging on functional group change, the hydrogen bonding behavior, and phase separated morphology. The results displayed prominent chain scission during aging, such as N–H, C=O, and C–O–C and the hydrogen bonded urea carbonyl content showed a decrease trend. The relative content of soft and hard segments showed a significant change, which increased the degree of phase separation. Full article

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

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15 pages, 4211 KiB

Open AccessArticle

Mechanical and Corrosion Resistance Enhancement of Closed-Cell Aluminum Foams through Nano-Electrodeposited Composite Coatings

by Yiku Xu, Shuang Ma, Mingyuan Fan, Hongbang Zheng, Yongnan Chen, Xuding Song and Jianmin Hao

Materials 2019, 12(19), 3197; https://doi.org/10.3390/ma12193197 - 29 Sep 2019

Cited by 9 | Viewed by 2780

Abstract

This work aims to improve the properties of aluminum foams including the mechanical properties and corrosion resistance by electrodepositing a SiC/TiN nanoparticles reinforced Ni–Mo coating on the substrate. The coatings were electrodeposited at different voltages, and the morphologies of the coating were detected [...] Read more.

This work aims to improve the properties of aluminum foams including the mechanical properties and corrosion resistance by electrodepositing a SiC/TiN nanoparticles reinforced Ni–Mo coating on the substrate. The coatings were electrodeposited at different voltages, and the morphologies of the coating were detected by SEM (scanning electron microscope) to determine the most suitable voltage. We used XRD (x-ray diffraction) and TEM (transmission electron microscope) to analyze the structure of the coatings. The aluminum foams and the substrates on which the coatings were electrodeposited at a voltage of 6.0 V for different electrodeposition times were compressed on an MTS (an Electro-mechanical Universal Testing Machine) to detect the mechanical properties. The corrosion resistance before and after the electrodeposition experiment was also examined. The results showed that the coating effectively improved the mechanical properties. When the electrodeposition time was changed from 10 min to 40 min, the W_v of the aluminum foams increased from 0.852 J to 2.520 J and the σ_s increased from 1.06 MPa to 2.99 MPa. The corrosion resistance of the aluminum foams was significantly improved after being coated with the Ni–Mo–SiC–TiN nanocomposite coating. The self-corrosion potential, pitting potential, and potential for primary passivation were positively shifted by 294 mV, 99 mV, and 301 mV, respectively. The effect of nanoparticles on the corrosion resistance of the coatings is significant. Full article

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

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16 pages, 8951 KiB

Open AccessArticle

Microstructure and Corrosion Resistance of Zn-Al Diffusion Layer on 45 Steel Aided by Mechanical Energy

by Jianbin Tong, Yi Liang, Shicheng Wei, Hongyi Su, Bo Wang, Yuzhong Ren, Yunlong Zhou and Zhongqi Sheng

Materials 2019, 12(18), 3032; https://doi.org/10.3390/ma12183032 - 18 Sep 2019

Cited by 3 | Viewed by 3368

Abstract

In harsh environments, the corrosion damage of steel structures and equipment is a serious threat to the operational safety of service. In this paper, a Zn-Al diffusion layer was fabricated on 45 steel by the Mechanical Energy Aided Diffusion Method (MEADM) at 450 [...] Read more.

In harsh environments, the corrosion damage of steel structures and equipment is a serious threat to the operational safety of service. In this paper, a Zn-Al diffusion layer was fabricated on 45 steel by the Mechanical Energy Aided Diffusion Method (MEADM) at 450 °C. The microstructure and composition, the surface topography, and the electrochemical performance of the Zn-Al diffusion layer were analyzed before and after corrosion. The results show that the Zn-Al diffusion layer are composed of Al₂O₃ and Γ₁ phase (Fe11Zn40) and δ₁ phase (FeZn_6.67, FeZn_8.87, and FeZn_10.98) Zn-Fe alloy. There is a transition zone with the thickness of about 5 μm at the interface between the Zn-Al diffusion layer and the substrate, and a carbon-rich layer exists in this zone. The full immersion test and electrochemical test show that the compact corrosion products produced by the initial corrosion of the Zn-Al diffusion layer will firmly bond to the Zn-Al diffusion layer surface and fill the crack, which plays a role in preventing corrosion of the corrosive medium and reducing the corrosion rate of the Zn-Al diffusion layer. The salt spray test reveals that the initial corrosion products of the Zn-Al diffusion layer are mainly ZnO and Zn₅(OH)₈Cl₂H₂O. New corrosion products such as ZnAl₂O₄, FeOCl appear at the middle corrosion stage. The corrosion product ZnAl₂O₄ disappears, and the corrosion products Zn(OH)₂ and Al(OH)₃ appear at the later corrosion stage. Full article

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

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15 pages, 8593 KiB

Open AccessArticle

Electrochemical Corrosion Behavior of Ni-Fe-Co-P Alloy Coating Containing Nano-CeO₂ Particles in NaCl Solution

by Xiuqing Fu, Wenke Ma, Shuanglu Duan, Qingqing Wang and Jinran Lin

Materials 2019, 12(16), 2614; https://doi.org/10.3390/ma12162614 - 16 Aug 2019

Cited by 15 | Viewed by 3177

Abstract

In order to study the effect of nano-CeO₂ particles doping on the electrochemical corrosion behavior of pure Ni-Fe-Co-P alloy coating, Ni-Fe-Co-P-CeO₂ composite coating is prepared on the surface of 45 steel by scanning electrodeposition. The morphology, composition, and phase structure of [...] Read more.

In order to study the effect of nano-CeO₂ particles doping on the electrochemical corrosion behavior of pure Ni-Fe-Co-P alloy coating, Ni-Fe-Co-P-CeO₂ composite coating is prepared on the surface of 45 steel by scanning electrodeposition. The morphology, composition, and phase structure of the composite coating are analyzed by means of scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The corrosion behavior of the coatings with different concentrations of nano-CeO₂ particles in 50 g/L NaCl solution is studied by Tafel polarization curve and electrochemical impedance spectroscopy. The corrosion mechanism is discussed. The experimental results show that the obtained Ni-Fe-Co-P-CeO₂ composite coating is amorphous, and the addition of nano-CeO₂ particles increases the mass fraction of P. With the increase of the concentration of nano-CeO₂ particles in the plating solution, the surface flatness of the coating increases. The surface of Ni-Fe-Co-P-1 g/L CeO₂ composite coating is uniform and dense, and its self-corrosion potential is the most positive; the corrosion current and corrosion rate are the smallest, and the charge transfer resistance is the largest, showing the best corrosion resistance. Full article

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

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15 pages, 7929 KiB

Open AccessArticle

Corrosion Resistance and Apatite-Forming Ability of Composite Coatings formed on Mg–Al–Zn–Ca Alloys

by Anawati Anawati, Hidetaka Asoh and Sachiko Ono

Materials 2019, 12(14), 2262; https://doi.org/10.3390/ma12142262 - 14 Jul 2019

Cited by 6 | Viewed by 2852

Abstract

The properties of composite coatings formed by plasma electrolytic oxidation (PEO) were affected by the alloy composition. The corrosion resistance and apatite-forming ability of PEO coatings formed on Mg–6Al–1Zn–xCa alloys with a variation of Ca content were investigated. Potentiodynamic polarization and electrochemical impedance [...] Read more.

The properties of composite coatings formed by plasma electrolytic oxidation (PEO) were affected by the alloy composition. The corrosion resistance and apatite-forming ability of PEO coatings formed on Mg–6Al–1Zn–xCa alloys with a variation of Ca content were investigated. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements showed an order magnitude improvement of corrosion resistance in the AZ61 alloy as a result of the coating. A higher enhancement in polarization resistance was obtained in the Mg–6Al–1Zn–1Ca and Mg–6Al–1Zn–2Ca alloys due to thicker coatings were formed as a result of the incorporation of calcium oxide/hydroxide. However, the underlying substrates were more prone to localized corrosion with increasing Ca content. The microstructure investigation revealed an enlargement in precipitates (Al₂Ca, Mg₂Ca) sizes with increasing Ca content in the alloys. The growth of larger size precipitates increased the danger to micro galvanic corrosion. Apatite layers were formed on all of the coatings indicating high apatite-forming ability, but the layers formed on the Mg–6Al–1Zn–1Ca and Mg–6Al–1Zn–2Ca alloys contained higher Mg, possibly due to the accumulation of corrosion product, than that on the Mg–6Al–1Zn alloy. The alloying element Ca should be limited to 1 wt.% as the excess tended to degrade the corrosion resistance and apatite-forming ability of the PEO coating. Full article

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

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11 pages, 4167 KiB

Open AccessArticle

Mechanically Robust and Repairable Superhydrophobic Zinc Coating via a Fast and Facile Method for Corrosion Resisting

by Junfei Ou, Wenhui Zhu, Chan Xie and Mingshan Xue

Materials 2019, 12(11), 1779; https://doi.org/10.3390/ma12111779 - 31 May 2019

Cited by 10 | Viewed by 2777

Abstract

Zinc coatings and superhydrophobic surfaces have their own characteristics in terms of metal corrosion resistance. Herein, we have prepared a robust and repairable superhydrophobic zinc coating (SZC) based on a widely commercially available cold galvanized paint via a fast (within 10 min) and [...] Read more.

Zinc coatings and superhydrophobic surfaces have their own characteristics in terms of metal corrosion resistance. Herein, we have prepared a robust and repairable superhydrophobic zinc coating (SZC) based on a widely commercially available cold galvanized paint via a fast (within 10 min) and facile process for corrosion resistance. Specifically, the cold galvanized paint was sprayed onto the iron substrate, followed by acetic acid (HAc) etching and stearic acid (STA) hydrophobizing. The as-obtained sample was coded as Fe-Zn-HAc-STA and possessed an apparent contact angle of 168.4 ± 1.5° as well as a sliding angle of 3.5 ± 1.2°. The Fe-Zn-HAc-STA sample was mechanically durable and easily repairable. After being ultrasonicated in ethanol for 100 min, the superhydrophobicity was still retained. The Fe-Zn-HAc-STA sample lost its superhydrophobicity after being abraded against sandpaper with a load of 100 g and regained its superhydrophobicity after HAc etching and subsequent STA hydrophobizing. The corrosion resistance of the SZC was investigated by immersing the Fe-Zn-HAc-STA sample into the static or dynamic aqueous solution of NaCl (3.5 wt.%) and the lasting life of the entrapped underwater air layer (EUAL) was roughly determined by the turning point at the variation curve of surface wettability against immersion time. The lasting life of the EUAL iwas 8 to 10 days for the SZC in the static NaCl solution and it decreased sharply to 12 h in a dynamic one with the flow rate of 2 and 4 m/s. This suggests that the superhydrophobic surface provided extra corrosion protection of 8 to 10 days or 12 h to the zinc coating. We hope that the SZC may find its practical application due to the facile and fast fabrication procedure, the good mechanical durability, the easy repairability, and the good corrosion protection. Full article

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

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8 pages, 2707 KiB

Open AccessArticle

Optimization of Cathodic Protection Design for Pre-Insulated Pipeline in District Heating System Using Computational Simulation

by Min-Sung Hong, Yoon-Sik So and Jung-Gu Kim

Materials 2019, 12(11), 1761; https://doi.org/10.3390/ma12111761 - 30 May 2019

Cited by 18 | Viewed by 3857

Abstract

Cathodic protection (CP) has been used as a primary method in the control of corrosion, therefore it is regarded as the most effective way for protecting buried pipelines. However, it is difficult to apply CP to a pipeline for district heating distribution systems, [...] Read more.

Cathodic protection (CP) has been used as a primary method in the control of corrosion, therefore it is regarded as the most effective way for protecting buried pipelines. However, it is difficult to apply CP to a pipeline for district heating distribution systems, because the pipeline has thermally insulated coatings which could disturb the CP. Theoretical calculation and field tests alone are not enough for a reliable CP design, and therefore additional CP design methods such as computational analysis should be used. In this study, the CP design for pre-insulated pipelines is tested considering several environmental factors, such as temperature and coating defect ratio. Additionally, computational analysis is performed to verify and optimize the CP design. The simulation results based on theoretical methods alone failed to satisfy the CP criteria. Then, a re-design is conducted considering the IR drop. Consequently, all of the simulation results of defective pipelines satisfied the CP criteria after adding the proper CP current. Full article

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

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13 pages, 4086 KiB

Open AccessArticle

Lotus-Inspired Multiscale Superhydrophobic AA5083 Resisting Surface Contamination and Marine Corrosion Attack

by Binbin Zhang, Weichen Xu, Qingjun Zhu, Shuai Yuan and Yantao Li

Materials 2019, 12(10), 1592; https://doi.org/10.3390/ma12101592 - 15 May 2019

Cited by 33 | Viewed by 3936

Abstract

The massive and long-term service of 5083 aluminum alloy (AA5083) is restricted by several shortcomings in marine and industrial environments, such as proneness to localized corrosion attack, surface contamination, etc. Herein, we report a facile and cost-effective strategy to transform intrinsic hydrophilicity into [...] Read more.

The massive and long-term service of 5083 aluminum alloy (AA5083) is restricted by several shortcomings in marine and industrial environments, such as proneness to localized corrosion attack, surface contamination, etc. Herein, we report a facile and cost-effective strategy to transform intrinsic hydrophilicity into water-repellent superhydrophobicity, combining fluorine-free chemisorption of a hydrophobic agent with etching texture. Dual-scale hierarchical structure, surface height relief and surface chemical elements were studied by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), successively. Detailed investigations of the wetting property, self-cleaning effect, NaCl-particle self-propelling, corrosion and long-term behavior of the consequent superhydrophobic AA5083 surface were carried out, demonstrating extremely low adhesivity and outstanding water-repellent, self-cleaning and corrosion-resisting performance with long-term stability. We believe that the low cost, scalable and fluorine-free transforming of metallic surface wettability into waterproof superhydrophobicity is a possible strategy towards anti-contamination and marine anti-corrosion. Full article

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

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2 pages, 190 KiB

Open AccessCorrection

Correction: Lara-Banda, M., et al. Alternative to Nitric Acid Passivation of 15-5 and 17-4PH Stainless Steel Using Electrochemical Techniques. Materials 2020, 13, 2836

by María Lara-Banda, Citlalli Gaona-Tiburcio, Patricia Zambrano-Robledo, Marisol Delgado-E, José A. Cabral-Miramontes, Demetrio Nieves-Mendoza, Erick Maldonado-Bandala, Francisco Estupiñan-López, José G. Chacón-Nava and Facundo Almeraya-Calderón

Materials 2020, 13(23), 5322; https://doi.org/10.3390/ma13235322 - 24 Nov 2020

Cited by 1 | Viewed by 1252

Abstract

The author wishes to make the following correction to this paper [...] Full article

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

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