Research

25 pages, 3708 KiB

Open AccessArticle

Effect of Iron Content on the Pitting Corrosion Behavior of Laser-Cladded Ni-Cr-Mo Alloy Coating in a Simulated Seawater Environment

by Quanbing Liu, Zongde Liu, Yue Shen, Yao Kong, Jiaxuan Li, Yutong Zhang and Huaqing Ning

Coatings 2024, 14(4), 459; https://doi.org/10.3390/coatings14040459 - 10 Apr 2024

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Abstract

In order to study the effect of iron content on the pitting corrosion behavior of a Ni-Cr-Mo alloy coating in a simulated seawater environment, a Ni-Cr-Mo-xFe (x = 0, 5, 10, 15, 20, 25) alloy coating was prepared through laser cladding technology. These [...] Read more.

In order to study the effect of iron content on the pitting corrosion behavior of a Ni-Cr-Mo alloy coating in a simulated seawater environment, a Ni-Cr-Mo-xFe (x = 0, 5, 10, 15, 20, 25) alloy coating was prepared through laser cladding technology. These coatings primarily consist of a γ-Ni solid solution phase, with observable iron segregation in the interdendritic regions when the iron content reaches 25 wt%. After 42 days of salt spray corrosion, it was found that pitting began to appear on the surface when the iron content in the coating increased to 10 wt%. The results of electrochemical behavior revealed that the coatings with iron contents in a range of 10–25 wt% exhibited metastable pitting characteristics, and the impedance modulus decreased with the increase in iron content. Pitting corrosion occurs due to selective corrosion of the dendritic regions. When the iron content exceeds 10 wt%, the accumulation of iron in the outer layer of the passivation film would lead to an excess of cationic vacancies, and the stability of the passive film is then reduced. This study provides a reference for the control of the iron content in a Ni-Cr-Mo alloy coating when applied in marine environments. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings)

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20 pages, 33298 KiB

Open AccessArticle

Aluminum Guefoams Coated with Reduced Graphene Oxide: A Corrosion Protection Study

by Rubén Rodrigo, Javier Molina, José Bonastre, Lucila P. Maiorano, José M. Molina and Francisco Cases

Coatings 2024, 14(2), 201; https://doi.org/10.3390/coatings14020201 - 04 Feb 2024

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Abstract

To enhance their corrosion protection, Guefoams were coated with RGO using both potentiostatic and potentiodynamic methods. The potentiodynamic method produced the thickest RGO coating and the lowest Cl, O, and Al content, as observed using FESEM and EDX. The Guefoams were exposed to [...] Read more.

To enhance their corrosion protection, Guefoams were coated with RGO using both potentiostatic and potentiodynamic methods. The potentiodynamic method produced the thickest RGO coating and the lowest Cl, O, and Al content, as observed using FESEM and EDX. The Guefoams were exposed to a 3.5% NaCl solution and steam. The polarization resistance was examined, electrochemical impedance spectroscopy was performed, and polarization curves were constructed to monitor the corrosion process. After 28 days, the Al concentrations in the solutions were measured, and were found to be 145 mg/L (bare Guefoam), 70 mg/L (RGO-coated, potentiostatic), and 35 mg/L (RGO-coated, potentiodynamic). The potentiodynamic RGO coating also showed the best corrosion protection values. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings)

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14 pages, 11562 KiB

Open AccessArticle

The Effect of Laser-Cladded Co6, T400, and Ni-Based 30WC Coatings on the Wear Resistance of H13 Steel

by Haibo Zhang, Jingyu Zhuang and Juncheng Li

Coatings 2024, 14(1), 114; https://doi.org/10.3390/coatings14010114 - 15 Jan 2024

Viewed by 662

Abstract

To enhance the wear resistance of H13 steel (4Cr5MoSiV1), Co6, T400, and Ni-based 30WC coatings were applied to the surface of H13 steel using laser cladding technology. The microstructures and phase compositions of the three coating types were analyzed using SEM and XRD [...] Read more.

To enhance the wear resistance of H13 steel (4Cr5MoSiV1), Co6, T400, and Ni-based 30WC coatings were applied to the surface of H13 steel using laser cladding technology. The microstructures and phase compositions of the three coating types were analyzed using SEM and XRD methods. The high-temperature friction and wear performance of the three coated samples and H13 steel were measured through high-temperature friction wear tests, and the friction wear types of the four samples were analyzed. A comparative analysis of experimental data led to the following conclusions: (1) Among the four samples, the Ni-based 30WC-coated sample exhibited the best self-lubricating properties. (2) The average wear area of H13 steel was 0.059 mm², and the wear volume was 0.29 mm³; the average wear area of Co6-coated samples was 0.050 mm², and the wear volume was 0.25 mm³; the average wear area of T400-coated samples was 0.002 mm², and the wear volume was 0.01 mm³; and the average wear area of the Ni-based 30WC-coated sample was 0.035 mm², and the wear volume was 0.17 mm³. In terms of wear resistance, the ranking from highest to lowest was: T400-coated sample > Ni-based 30WC-coated sample > Co6-coated sample > H13 steel. (3) Based on the classification of friction wear types, H13 steel primarily exhibited adhesive wear and oxidized wear; the Co6- and T400-coated samples primarily showed adhesive wear, abrasive wear and oxidized wear; and the Ni-based 30WC-coated sample mainly exhibited abrasive wear and oxidized wear. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings)

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11 pages, 6759 KiB

Open AccessArticle

Effects of Base Metal Preheating on the Microstructure, Mechanical Properties, and Corrosion Resistance of UNS S32750 SDSS Pulsed Nd:YAG Laser Welding

by Eli J. da Cruz Junior, Francisco M. F. A. Varasquim, Gillian S. Crespo, Vicente. A. Ventrella, Andrea Zambon and Irene Calliari

Coatings 2023, 13(11), 1930; https://doi.org/10.3390/coatings13111930 - 11 Nov 2023

Viewed by 700

Abstract

Super duplex stainless steel has a microstructure consisting of equal proportions of austenite and ferrite. However, welding with Nd:YAG pulsed laser results in an imbalanced microstructure that compromises the steel’s properties. This paper studied the effects of preheating the base metal on pulsed [...] Read more.

Super duplex stainless steel has a microstructure consisting of equal proportions of austenite and ferrite. However, welding with Nd:YAG pulsed laser results in an imbalanced microstructure that compromises the steel’s properties. This paper studied the effects of preheating the base metal on pulsed Nd:YAG laser welding. Four conditions were evaluated (no preheating and heating at 100 °C, 200 °C, and 300 °C). The analysis included studying the microstructure, microhardness, and corrosion resistance. Preheating the base metals was found to be an effective method for increasing the volume fractions of austenite. The preheated samples showed an improvement in corrosion resistance compared to the untreated sample. The microhardness varied, with the ferrite amount being higher in the untreated sample. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings)

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18 pages, 3744 KiB

Open AccessArticle

Influence of NaCl Solution External Erosion on Corrosion Resistance of RPC Reinforced with Straw Fiber

by Zihao Cao, Kewei Wang, Xi Peng, Hui Wang and Rongming Huang

Coatings 2023, 13(8), 1308; https://doi.org/10.3390/coatings13081308 - 26 Jul 2023

Cited by 1 | Viewed by 806

Abstract

Straw fiber, as a kind of waste if not properly treated, will pollute the environment. It can be used in cement-based materials as a plant fiber material. Agricultural solid-waste straw fiber has good tensile properties and is expected to be used as a [...] Read more.

Straw fiber, as a kind of waste if not properly treated, will pollute the environment. It can be used in cement-based materials as a plant fiber material. Agricultural solid-waste straw fiber has good tensile properties and is expected to be used as a fiber-reinforced material for reactive powder concrete (RPC) and to improve the corrosion resistance of RPC. In this paper, the ultrasonic velocity through specimens, the electrical resistance, the AC impedance spectroscopy and tafel curve were analyzed. The corrosion resistance of the steel bar under the chloride salt freeze–thaw cycles and dry–wet alternations was systematically studied. The result shows that adding a certain content of straw fiber can improve its corrosion resistance. Under the action of two chloride salt environments, the lowest mass loss rate was 0.82% for the sample with 3% straw fiber content and the mass growth rate of the specimens with 4% straw fiber is the highest aqt 0.9%. In terms of ultrasonic velocity, the lowest loss rate was 5.68% for specimens with fiber content of 2%. The specimens were subjected to 0 dry–wet alternations and freeze–thaw cycles; the highest electrical resistance is 19.96 kΩ when the fiber content is 1% and the lowest electrical resistance is 11.105 kΩ when the fiber content is 2%. Under the dry–wet alternations, the content of straw fiber and its corrosion resistance are: 1% > 4% > 0% > 3% > 2%. Under freeze–thaw cycles, the content of straw fiber and its corrosion resistance were as follows: 1% > 0% > 4% > 3% > 2%. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings)

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16 pages, 3643 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of the Mechanical and Corrosion Behavior of Twin Wire Arc Sprayed Ni-Al Coatings with Different Al and Mo Content

by Jaehui Bang and Eunkyung Lee

Coatings 2023, 13(6), 1069; https://doi.org/10.3390/coatings13061069 - 09 Jun 2023

Cited by 2 | Viewed by 1004

Abstract

In this study, the surface properties of marine structures were improved by applying a twin wire arc spray process to high-strength low alloys. The effect of Al and Mo contents in Ni-Al coatings on their mechanical and corrosion behaviors was analyzed using hardness [...] Read more.

In this study, the surface properties of marine structures were improved by applying a twin wire arc spray process to high-strength low alloys. The effect of Al and Mo contents in Ni-Al coatings on their mechanical and corrosion behaviors was analyzed using hardness tests, electrochemical experiments, and immersion tests. The increase in Al content resulted in the formation of oxides and intermetallic compounds, leading to a significant improvement in the mechanical properties by approximately 222 HV. Despite a fine galvanic phenomenon causing a decrease in corrosion resistance by up to 8.91%, a higher Al content demonstrated the highest corrosion resistance after high-temperature exposure, with an enhancement of approximately 20.9%, attributed to the formation of an oxide film generated by intermetallic phase transformation. However, the mechanical properties experienced a reduction of 134.3 HV. This study demonstrated a correlation between the microstructure of the coating layers that form passivation films and their respective mechanical and corrosion properties. It also revealed that the content of Al and Mo significantly affects the mechanical and corrosion behavior of Ni-Al coatings. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings)

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15 pages, 4129 KiB

Open AccessArticle

Processing and Analysis of Micro-Arc Oxidation Coating on 319S Aluminum Alloy

by Pengxiang Lv, Xiaozhou Zhang, Tingting Yin, Zhen Wang, Qi Dong, Li He and Shuangyang Zheng

Coatings 2023, 13(6), 1024; https://doi.org/10.3390/coatings13061024 - 31 May 2023

Cited by 1 | Viewed by 1368

Abstract

In this study, a high-hardness and wear-resistant ceramic coating was prepared on the surface of 319S aluminum alloy using the micro-arc oxidation (MAO) technique. The effects of pulse width, negative voltage, and KOH concentration on the MAO coating were investigated, and the microhardness [...] Read more.

In this study, a high-hardness and wear-resistant ceramic coating was prepared on the surface of 319S aluminum alloy using the micro-arc oxidation (MAO) technique. The effects of pulse width, negative voltage, and KOH concentration on the MAO coating were investigated, and the microhardness and surface roughness of the coating were measured. The morphology, elemental distribution, and phase composition of the coating were analyzed using SEM, EDS, XRD, and digital microscopy. The influence of the MAO coating on the wear of the 319S aluminum alloy was evaluated using a friction-wear tester. The results showed that in the sodium silicate solution system, with an increase in pulse width, the thickness of the coating gradually increased and the surface hardness initially increased and then decreased. With an increase in negative voltage, the density of the coating first increased and then decreased, the thickness of the dense layer initially increased and then decreased, and the surface hardness initially increased and then decreased. With an increase in the KOH concentration, the coating thickness increased and the roughness initially decreased and then increased. When the pulse width was 3000 ms, the negative voltage was 130 V, and the KOH concentration was 1 g/L, the coating exhibited the best density, with the highest surface hardness of 1426.8 HV and the thickest dense layer of 55 μm. The reduction in surface cracks and improvement in density indicated an enhancement in the hardness and wear resistance of the coating. The decrease in width and depth of the wear scars demonstrated the excellent wear resistance of the coating. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings)

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8 pages, 2624 KiB

Open AccessCommunication

Electrochemical Dealloying Preparation and Morphology Evolution of Nanoporous Au with Enhanced SERS Activity

by Fei Li, Silang Luo, Fengsheng Qu, Dou Wang, Chao Li and Xue Liu

Coatings 2023, 13(3), 489; https://doi.org/10.3390/coatings13030489 - 22 Feb 2023

Cited by 1 | Viewed by 1076

Abstract

Nanoporous Au (NPG) prepared by dealloying is one of the most used substrates for surface-enhanced Raman scattering (SERS). The morphology tailoring of the NPG to obtain both ultrafine pores and suitable Au/Ag ratio is of great importance for the acquiring of enhanced SERS [...] Read more.

Nanoporous Au (NPG) prepared by dealloying is one of the most used substrates for surface-enhanced Raman scattering (SERS). The morphology tailoring of the NPG to obtain both ultrafine pores and suitable Au/Ag ratio is of great importance for the acquiring of enhanced SERS performance. Compared with the chemical dealloying, the electrochemical dealloying can tailor the NPG to be more flexible by the additional adjustment of dealloying voltage and current. Thus, further understanding on the morphology evolution of NPG during the electrochemical dealloying to obtain enhanced SERS performance is of great importance. In the presented work, the morphology and composition evolution of the NPG film during the electrochemical dealloying was investigated. NPG films with a stable pore diameter of approximately 11 nm as well as diverse compositions were obtained by electrochemical dealloying an Au-Ag alloy film. The prepared NPG film exhibits an enhanced SERS activity with an enhancement factor (EF) of 7.3 × 10⁶ and an excellent detection limit of 10⁻⁹ M. This work provides insights into the morphology and composition evolution of the NPG during the electrochemical dealloying process to obtain enhanced SERS performance. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings)

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17 pages, 5284 KiB

Open AccessArticle

High-Velocity Oxy-Fuel (HVOF) Spray Coating of Inconel, Colmonoy, and Aluminum on AISI 316L Stainless Steel: A Comparative Investigation of the Microstructure and Corrosion Resistance of Coatings

by M. Taghian, M. Heydarian, S. Torkian, M. Parham Dabir, A. Bahrami, S. H. Mousavi Anijdan and N. Park

Coatings 2023, 13(1), 204; https://doi.org/10.3390/coatings13010204 - 16 Jan 2023

Cited by 1 | Viewed by 2138

Abstract

This study examines the effect of high-velocity oxy-fuel (HVOF) coatings of Inconel, aluminum, and Colmonoy on the corrosion resistance of stainless steel substrates. The coated samples were characterized using SEM, XRD, and EDS techniques. Impedance and Tafel tests were used to investigate the [...] Read more.

This study examines the effect of high-velocity oxy-fuel (HVOF) coatings of Inconel, aluminum, and Colmonoy on the corrosion resistance of stainless steel substrates. The coated samples were characterized using SEM, XRD, and EDS techniques. Impedance and Tafel tests were used to investigate the coatings corrosion responses at 40, 50, and 60 °C. Inconel-coated specimens showed superior corrosion behavior thanks to the Cr₂O₃ layers formed between the lamella structures of the coating, preventing chloride ions from diffusing across the coating. Although the Nyquist curve indicated oxide layer formation for the Al-coated sample, the Tafel test results showed severe corrosion. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings)

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16 pages, 4336 KiB

Open AccessArticle

Pitting Performance of Cold- and Hot-Rolled Nickel-Saving High-Strength Metastable Austenitic Stainless Steel

by Siyuan Lu, Chaoyang Zou, Riqing Huang, Yiming Qiu, Shuheng Qiu and Chi Zhang

Coatings 2022, 12(12), 1869; https://doi.org/10.3390/coatings12121869 - 01 Dec 2022

Viewed by 1118

Abstract

Nowadays, nickel-saving metastable austenitic stainless steel (MASS) has become the right solution to meeting the growing requirement of higher strength, better corrosion resistance and more cost saving for the automobile industry. Better understanding of the pitting mechanism of the MASS after either cold- [...] Read more.

Nowadays, nickel-saving metastable austenitic stainless steel (MASS) has become the right solution to meeting the growing requirement of higher strength, better corrosion resistance and more cost saving for the automobile industry. Better understanding of the pitting mechanism of the MASS after either cold- or hot-rolled can offer guidance for the producing of high-performance automobile steel. In the current work, for uncovering the pitting mechanism of the cold- and hot-rolled MASS, the microstructural evolution and pitting performance of nickel-saving metastable austenitic stainless (MASS) steel after cold- (CR) and hot-rolling (HR) were researched via electron microscopy technique and electrochemical methods. Austenite composites the main phase of the MASS. Small amounts of martensite film were proven to form in the MASS. The precipitation of Cr-rich M₂₃C₆ carbides was observed in the CR-MASS, while no carbides existed in the HR-MASS. The pitting resistance of the HR-MASS was better than the CR-MASS, which could be attributed to the fact that the stable pits in CR-MASS were initiated near the carbides, whereas the MnS inclusion would serve as the initiation sites for stable pits in HR-MASS. Findings in this work will provide a guidance for developing new generation MASS for automobile industry. Full article

(This article belongs to the Special Issue Corrosion Resistance, Mechanical Properties and Characterization of Metallic Materials and Coatings)

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