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3 pages, 191 KiB

Open AccessEditorial

Special Issue “Corrosion Resistance of Alloy and Coating Materials”

by Zbigniew Brytan

Materials 2022, 15(17), 6127; https://doi.org/10.3390/ma15176127 - 3 Sep 2022

Viewed by 1390

Abstract

This Special Issue aims to include the latest research findings on the corrosion phenomena that occur in various materials, both solid and coating materials [...] Full article

(This article belongs to the Special Issue Corrosion Resistance of Alloy and Coating Materials)

Research

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17 pages, 4472 KiB

Open AccessArticle

Microstructure and Corrosion Resistance of AZ91 Magnesium Alloy after Surface Remelting Treatment

by Józef Iwaszko and Monika Strzelecka

Materials 2022, 15(24), 8980; https://doi.org/10.3390/ma15248980 - 15 Dec 2022

Cited by 10 | Viewed by 1752

Abstract

The effect of surface remelting treatment on the microstructure and corrosion resistance of the AZ91 magnesium alloy was studied. The surface layer was remelted by GTAW (gas tungsten arc welding). An original two-burner system with welding torches operating in a tandem configuration was [...] Read more.

The effect of surface remelting treatment on the microstructure and corrosion resistance of the AZ91 magnesium alloy was studied. The surface layer was remelted by GTAW (gas tungsten arc welding). An original two-burner system with welding torches operating in a tandem configuration was used, allowing the combination of cleaning the surface from oxides with the remelting process. The studies of the corrosion resistance of the alloy included electrochemical tests and measurements of the rate of hydrogen evolution. The results showed that surface remelting treatment leads to favorable microstructural changes, manifested in strong grain refinement and a more uniform arrangement of the β-Mg₁₇Al₁₂ phase. The changes in the microstructure caused by remelting and the accompanying fast crystallization contributed to an increase in the corrosion resistance of the remelted samples in comparison to their non-remelted equivalents. The results obtained on the basis of the polarization curves showed three-fold lower values of the corrosion current density in the case of the remelted material than the value of the corrosion current density determined for the starting material. In turn, in the case of measurements of the electrochemical noise and corrosion rate determined by the method of measuring the rate of hydrogen evolution, this value for the remelted alloy was two times lower. The research also showed that GTAW technology is highly effective and can be a valuable alternative to laser techniques. The complete experimental details, obtained results and their analyses are presented in this paper. Full article

(This article belongs to the Special Issue Corrosion Resistance of Alloy and Coating Materials)

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17 pages, 7581 KiB

Open AccessEditor’s ChoiceArticle

Influence of Filler Metal on Electrochemical Characteristics of a Laser-Welded CoCrMoW Alloy Used in Prosthodontics

by Lukasz Reimann, Zbigniew Brytan and Grzegorz Jania

Materials 2022, 15(16), 5721; https://doi.org/10.3390/ma15165721 - 19 Aug 2022

Cited by 5 | Viewed by 1824

Abstract

This paper sought to determine corrosion resistance changes in the artificial saliva of a CoCrMoW-based alloy used for dental prostheses under Nd:YAG laser welding with CoCr alloy and stainless steel wire filler metals. The paper presents the corrosion characteristics of such joints, including [...] Read more.

This paper sought to determine corrosion resistance changes in the artificial saliva of a CoCrMoW-based alloy used for dental prostheses under Nd:YAG laser welding with CoCr alloy and stainless steel wire filler metals. The paper presents the corrosion characteristics of such joints, including the next stage of porcelain-fused-to-metal (PFM) firing. Corrosion tests were performed by electrochemical methods registering anodic polarization curves and electrochemical impedance spectroscopy (EIS). The microstructures were assessed by scanning microscopy (SEM) and chemical composition analysis (EDS) at the connection and heat-affected zones. Welding CoCrMoW alloy with and without a filler material increased the open circuit potential of the samples by 40–100 mV compared to unwelded base alloy. At the same time, a potentiodynamic test showed a polarization resistance R_pol reduction in welded samples, both for CoCr and stainless steel wires, as compared to the base CoCrMoW material. On the other hand, when comparing the current density and polarization resistance between materials welded with two different filler metals, better results were obtained for samples welded with stainless steel wire. The polarization resistance R_pol for the base alloy was 402 kΩ·cm², for the CoCr wire weld it was 436 kΩ·cm², and the value was 452 kΩ·cm² for stainless steel wire welds. Comparing polarization resistance R_pol from the Tafel analysis and the total charge transfer resistance from Rp_(EIS) from EIS, the CoCrMoW alloy welded with a stainless steel wire after heat treatment equaled or even slightly exceeded the corrosion resistance of the base alloy and alloy welded with dedicated CoCr wire after heat treatment. These results indicated the possibility of using stainless steel wire for the laser welding of CoCrMoW alloys dental prostheses, including the next stage of PFM, without sacrificing the corrosion resistance of such connections, and this was confirmed by most electrochemical parameters. Full article

(This article belongs to the Special Issue Corrosion Resistance of Alloy and Coating Materials)

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13 pages, 4854 KiB

Open AccessArticle

Electrochemical Evaluation of Protective Coatings with Ti Additions on Mild Steel Substrate with Potential Application for PEM Fuel Cells

by Diana N. Avram, Corneliu M. Davidescu, Mircea L. Dan, Julia C. Mirza-Rosca, Iosif Hulka, Alexandru Pascu and Elena M. Stanciu

Materials 2022, 15(15), 5364; https://doi.org/10.3390/ma15155364 - 4 Aug 2022

Cited by 11 | Viewed by 2071

Abstract

In this work, the corrosion behavior of NiCr(Ti) protective coatings deposited on mild steel substrates through laser cladding technology is studied as an alternative new material for metallic bipolar plates used in PEMFC applications. For electrochemical testing, a solution consisting of 0.5 M [...] Read more.

In this work, the corrosion behavior of NiCr(Ti) protective coatings deposited on mild steel substrates through laser cladding technology is studied as an alternative new material for metallic bipolar plates used in PEMFC applications. For electrochemical testing, a solution consisting of 0.5 M H₂SO₄ + 2 ppm F⁻ at room temperature is used as an electrolyte. The fluoride ions are added to simulate the conditions in the PEM fuel cell due to degradation of the proton exchange membrane and fluoride release. A saturated calomel electrode (SCE) is used as a reference electrode and a platinum mesh as the counter electrode. Scanning electron microscopy (SEM) and optical microscopy (OM) are used for studying the morphology of the protective coatings and the effect of Ti addition. The electrochemical evaluation consisted of measuring the open circuit potential (OCP), followed by electrochemical impedance spectroscopy measurements (EIS) and potentiodynamic polarization. It is found that the coatings with 5% Ti, 7% Ti and 10% Ti addition comply with the conditions of the US DOE regarding corrosion performance to be used as materials for the manufacture of the bipolar plates. Full article

(This article belongs to the Special Issue Corrosion Resistance of Alloy and Coating Materials)

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16 pages, 8499 KiB

Open AccessEditor’s ChoiceArticle

Corrosion Behavior of the AlCoCrFeNi_2.1 Eutectic High-Entropy Alloy in Chloride-Containing Sulfuric Acid Solutions at Different Temperatures

by Longfei Song, Wenbin Hu, Xiaowen Zhang, Bokai Liao, Shan Wan, Lei Kang and Xingpeng Guo

Materials 2022, 15(14), 4822; https://doi.org/10.3390/ma15144822 - 11 Jul 2022

Cited by 13 | Viewed by 2086

Abstract

In this work, the influence of temperature on the corrosion behavior of AlCoCrFeN_i2.1 eutectic high-entropy alloy in a chloride-containing sulfuric acid solution was investigated using electrochemical measurement, X-ray photoelectron spectroscopy, and scanning electron microscopy. Results show that the passive film of AlCoCrFeN [...] Read more.

In this work, the influence of temperature on the corrosion behavior of AlCoCrFeN_i2.1 eutectic high-entropy alloy in a chloride-containing sulfuric acid solution was investigated using electrochemical measurement, X-ray photoelectron spectroscopy, and scanning electron microscopy. Results show that the passive film of AlCoCrFeN_i2.1 is stable in chloride-containing sulfuric acid solutions at low temperatures, while an unstable film forms on the alloy at high temperatures. Furthermore, temperature changes the proportion of hydroxide and oxide in Fe and Cr, but it has no noticeable effect on Al and Ni, which is a significant factor on the passive behavior. L12 phase exhibits good corrosion resistance at different temperatures. Pitting occurred on B2 phase in the chloride-containing sulfuric acid solution at a low temperature of 5 °C, while pitting and dissolution take place on AlCoCrFeNi_2.1 in the acid solution at room temperature and above. Full article

(This article belongs to the Special Issue Corrosion Resistance of Alloy and Coating Materials)

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20 pages, 6312 KiB

Open AccessArticle

The Influence of Casein Coatings on the Corrosion Behavior of Mg-Based Alloys

by Aneta Kania, Katarzyna Cesarz-Andraczke, Zbigniew Brytan, Łukasz Reimann and Paulina Smolarczyk

Materials 2022, 15(4), 1399; https://doi.org/10.3390/ma15041399 - 14 Feb 2022

Cited by 2 | Viewed by 1906

Abstract

This article discusses the influence of conversion casein coatings with a thickness of about 20 µm on the structure and the corrosion behavior of two magnesium alloys: MgCa2Zn1 and MgCa2Zn1Gd3. Casein is a protein that, along with whey protein, is a part of [...] Read more.

This article discusses the influence of conversion casein coatings with a thickness of about 20 µm on the structure and the corrosion behavior of two magnesium alloys: MgCa2Zn1 and MgCa2Zn1Gd3. Casein is a protein that, along with whey protein, is a part of milk. Casein coatings are appropriate for bone growth because they contain high amounts of calcium and phosphorus. In this work, casein coatings and casein-free coatings were applied on Mg-based alloys using the conversion process. The structure and topography observations were presented. The corrosion behavior was determined by electrochemical and immersion tests, and electrochemical impedance spectroscopy (EIS) in chloride-rich Ringer solution. The obtained results show that conversion casein coatings effectively protect Mg-based alloys against corrosion. This was confirmed by higher corrosion potentials (E_corr), polarization resistances (R_p) derived from Tafel’s and EIS analysis, as well as low hydrogen release. The volume of hydrogen released after 216 h of immersion for casein coatings applied to MgCa2Zn1 and MgCa2Zn1Gd3 alloys was 19.25 and 12.42 mL/cm², respectively. The improvement in corrosion resistance of casein coatings was more significant for Mg alloy dopped with gadolinium. The lower corrosion rate of casein conversion coatings is explained by the synergistic effect of the addition of Gd in the Mg-based alloy and the formation of dense, tight conversion casein coatings on the surface of this alloy. Full article

(This article belongs to the Special Issue Corrosion Resistance of Alloy and Coating Materials)

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21 pages, 15639 KiB

Open AccessArticle

Investigation of the Relationship between Degradation of the Coating of Gas Turbine Blades and Its Surface Color

by Mariusz Bogdan, Józef Błachnio, Artur Kułaszka and Dariusz Zasada

Materials 2021, 14(24), 7843; https://doi.org/10.3390/ma14247843 - 18 Dec 2021

Cited by 7 | Viewed by 2843

Abstract

This article presents issues concerning the relationship between the degradation of the coating of gas turbine blades and changes in the color of its surface. Conclusions were preceded by the determination of parameters characterizing changes in the technical condition of protective coatings made [...] Read more.

This article presents issues concerning the relationship between the degradation of the coating of gas turbine blades and changes in the color of its surface. Conclusions were preceded by the determination of parameters characterizing changes in the technical condition of protective coatings made based on a metallographic examination that defined the morphological modifications of the microstructure of the coating, chemical composition of oxides, and roughness parameters. It has been shown that an increased operating time causes parameters that characterize the condition of the blades to deteriorate significantly. Results of material tests were compared with those of blade surface color analyses performed using a videoscope. Image data were represented in two color models, i.e., RGB and L*a*b* with significant differences being observed between parameters in both representations. The study results demonstrated a relationship between the coating degradation degree and changes in the color of the blade’s surface. Among others, this approach may be used as a tool to assess the condition of turbine blades as well as entire gas turbines. Full article

(This article belongs to the Special Issue Corrosion Resistance of Alloy and Coating Materials)

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12 pages, 4390 KiB

Open AccessArticle

Salt Heat Treatment and Passivation to Improve the Corrosion Resistance of Nitinol (Ni-Ti)

by Inho Bae, Byung-Hoon Kim, Dong-Gon Kim, Ik-Bu Sohn and Seong-Won Yang

Materials 2021, 14(24), 7789; https://doi.org/10.3390/ma14247789 - 16 Dec 2021

Cited by 4 | Viewed by 2647

Abstract

Corrosion of nitinol (NiTi) is a major factor in the failure of implantable materials. Recently, as the importance of corrosion of metals has increased, testing according to international guidelines is essential. The purpose of this study was to evaluate the corrosion resistance of [...] Read more.

Corrosion of nitinol (NiTi) is a major factor in the failure of implantable materials. Recently, as the importance of corrosion of metals has increased, testing according to international guidelines is essential. The purpose of this study was to evaluate the corrosion resistance of NiTi wire through heat treatment and passivation process. In this study, NiTi wire used two commercially available products and a self-manufactured stent. Experimental consideration was carried out according to ASTM standards. Heat treatment was carried out in an air or a salt furnace, and the corrosion was measured after additional process, such as passivation and scratch tests. As a result, the metal potential was rapidly decreased in the air furnace group. On the other hand, the potential of wires was dramatically increased in the salt furnace group compared to the air furnace group. The dislocation decreased below the acceptance criteria (>600 mV) within 60 s of heat treatment time in the air furnace. Moreover, the potential was dramatically improved, even after only 20 min of passivation treatment (1076 mV, 442% compared to the non-passivated group), and it continued to rise until 180 min. This phenomenon was similarly observed in the group of self-manufactured stents. The potential slightly decreased by the scratch process (93.1%) was significantly reduced by the air furnace process (315 mV, 24.4% of the nontreated group). In the passivated group of the air furnace sample with reduced potential, the potential was restored to the level before the air furnace (scratch stage) (1032 mV). In conclusion, the heat treatment is preferably carried out in a salt furnace rather than an air furnace, and the passivation process can be an advantageous tool to improve corrosion resistance by suppressing the oxidation process. Full article

(This article belongs to the Special Issue Corrosion Resistance of Alloy and Coating Materials)

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18 pages, 5420 KiB

Open AccessArticle

Effect of TiO₂ Concentration on Microstructure and Properties of Composite Cu–Sn–TiO₂ Coatings Obtained by Electrodeposition

by Aliaksandr A. Kasach, Dzmitry S. Kharytonau, Andrei V. Paspelau, Jacek Ryl, Denis S. Sergievich, Ivan M. Zharskii and Irina I. Kurilo

Materials 2021, 14(20), 6179; https://doi.org/10.3390/ma14206179 - 18 Oct 2021

Cited by 9 | Viewed by 2230

Abstract

In this work, Cu–Sn–TiO₂ composite coatings were electrochemically obtained from a sulfate bath containing 0–10 g/L of TiO₂ nanoparticles. The effect of TiO₂ particles on kinetics of cathodic electrodeposition has been studied by linear sweep voltammetry and chronopotentiometry. As compared [...] Read more.

In this work, Cu–Sn–TiO₂ composite coatings were electrochemically obtained from a sulfate bath containing 0–10 g/L of TiO₂ nanoparticles. The effect of TiO₂ particles on kinetics of cathodic electrodeposition has been studied by linear sweep voltammetry and chronopotentiometry. As compared to the Cu–Sn alloy, the Cu–Sn–TiO₂ composite coatings show rougher surfaces with TiO₂ agglomerates embedded in the metal matrix. The highest average amount of included TiO₂ is 1.7 wt.%, in the case of the bath containing 5 g/L thereof. Composite coatings showed significantly improved antibacterial properties towards E. coli ATCC 8739 bacteria as compared to the Cu–Sn coatings of the same composition. Such improvement has been connected with the corrosion resistance of the composites studied by linear polarization and electrochemical impedance spectroscopy. In the bacterial media and 3% NaCl solutions, Cu–Sn–TiO₂ composite coatings have lower corrosion resistance as compared to Cu–Sn alloys, which is caused by the nonuniformity of the surface. Full article

(This article belongs to the Special Issue Corrosion Resistance of Alloy and Coating Materials)

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14 pages, 34420 KiB

Open AccessArticle

High-Temperature Corrosion of APS- and HVOF-Coated Nickel-Based Super Alloy under Air Oxidation and Melted Salt Domains

by Ibrahim A. Alnaser, Mohammed Yunus, Rami Alfattani and Turki Alamro

Materials 2021, 14(18), 5119; https://doi.org/10.3390/ma14185119 - 7 Sep 2021

Cited by 11 | Viewed by 2527

Abstract

Various thermal spraying approaches, such as air/atmospheric plasma spraying (APS) and high-velocity oxy-fuel (HVOF) spraying, are widely employed by plants owing to their flexibility, low costs and the high surface quality of the manufactured product. This study focuses on the corrosion behavior of [...] Read more.

Various thermal spraying approaches, such as air/atmospheric plasma spraying (APS) and high-velocity oxy-fuel (HVOF) spraying, are widely employed by plants owing to their flexibility, low costs and the high surface quality of the manufactured product. This study focuses on the corrosion behavior of a Ni superalloy coated with powder Cr₃C₂-25NiCr through APS and HVOF at 950 °C under air oxidation and Na₂SO₄ + 0.6V₂O₅ molten salt environments (MSE). The results show that HVOF-deposited Ni superalloys have higher hardness and bond strength than the respective APS coating. The thermo-gravimetric probe reveals that the Ni superalloys exposed to an oxidizing air environment has a minor mass gain compared to those under the MSE domain for both non-coated and coated samples, in line with the parabola curvature rate oxidizing law. The Ni superalloys show good corrosion resistance but poor oxidation resistance in APS-deposited Ni superalloys under the MSE. HVOF-coated Ni superalloys in both environments exhibit better corrosion resistance and lower mass gain than APS-coated superalloys. The excellent coating characteristics of HVOF-coated Ni superalloys lead to their better high-temperature corrosion performance than APS. Full article

(This article belongs to the Special Issue Corrosion Resistance of Alloy and Coating Materials)

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21 pages, 11567 KiB

Open AccessArticle

Structure and Properties of TiO₂/nanoTiO₂ Bimodal Coatings Obtained by a Hybrid PVD/ALD Method on 316L Steel Substrate

by Marcin Staszuk, Daniel Pakuła, Łukasz Reimann, Anna Kloc-Ptaszna, Mirosława Pawlyta and Antonín Kříž

Materials 2021, 14(16), 4369; https://doi.org/10.3390/ma14164369 - 4 Aug 2021

Cited by 8 | Viewed by 2194

Abstract

This paper presents the synergy of the effect of two surface engineering technologies—magnetron sputtering (MS-PVD) and atomic layer deposition (ALD) on the structure and properties of 316L steel. Recent studies indicate that PVD coatings, despite their thickness of a few micrometers, have many [...] Read more.

This paper presents the synergy of the effect of two surface engineering technologies—magnetron sputtering (MS-PVD) and atomic layer deposition (ALD) on the structure and properties of 316L steel. Recent studies indicate that PVD coatings, despite their thickness of a few micrometers, have many discontinuities and structural defects, which may lead to pitting corrosion after time. Applying an ALD layer to a PVD coating seals its structure and contributes to extending the service life of the coating. Investigations of the structure and morphology of the produced layers were carried out using a scanning electron microscope (SEM) and atomic force microscope (AFM). In addition, the structure of the coatings was investigated on the cross-section using a scanning-transmission electron microscope S/TEM. The tribological properties of the materials studied were determined by the ball-on-disc method. The corrosion resistance of the tested materials was determined by the electrochemical potentiodynamic method by recording the polarization curves of the anodes. Additional information about the electrochemical properties of the tested samples, including the quality, their tightness, and their resistivity, was obtained by electrochemical impedance spectroscopy (EIS). In addition, the main mechanisms of corrosion and tribological wear were determined by SEM observations after corrosion tests and after tribological tests. The study showed that the fabrication of hybrid layers by MS-PVD and ALD techniques allows obtaining coatings with electrochemical properties superior to those of layers fabricated by only one method. Full article

(This article belongs to the Special Issue Corrosion Resistance of Alloy and Coating Materials)

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18 pages, 4773 KiB

Open AccessArticle

Influence of Laser Treatment on the Corrosion Resistance of Cr₃C₂-25(Ni20Cr) Cermet Coating

by Mieczyslaw Scendo, Wojciech Zorawski, Katarzyna Staszewska-Samson and Anna Goral

Materials 2021, 14(15), 4078; https://doi.org/10.3390/ma14154078 - 22 Jul 2021

Cited by 4 | Viewed by 1758

Abstract

The influence of the laser treatment on the corrosion resistance of the Cr₃C₂-25(Ni20Cr) cermet coating on the Al7075 (EN, AW-7075) substrate (Cr₃C₂-25(Ni20Cr)/Al7075) was investigated. The coating was produced by the cold sprayed (CS) method. The [...] Read more.

The influence of the laser treatment on the corrosion resistance of the Cr₃C₂-25(Ni20Cr) cermet coating on the Al7075 (EN, AW-7075) substrate (Cr₃C₂-25(Ni20Cr)/Al7075) was investigated. The coating was produced by the cold sprayed (CS) method. The tested coatings were irradiated with a laser spot speed of 600 mm/min, 800 mm/min, and 1000 mm/min. The mechanical properties of the Cr₃C₂-25(Ni20Cr)/Al7075 were characterized by microhardness (HV) measurements. The surface and microstructure of the specimens were observed by ascanning electron microscope (SEM) and other assistive techniques. The corrosion test of materials wascarried out by using the electrochemical method in the acidic chloride solution. Cermet coatings perfectly protect the Al7075 substrate against contact with an aggressive corrosion environment. The laser remelting process of the Cr₃C₂-25(Ni20Cr) layer caused the homogenization of the structure cermet coatings. The irradiation with the laser beam eliminates microcracks and pores on the Cr₃C₂-25(Ni20Cr) surface. However, the best effect of improving the anti-corrosion properties of cermet coating was obtained for the lowest laser spot speed (i.e., 600 mm/min). It was found that the corrosion rate of the Cr₃C₂-25(Ni20Cr) cermet coating was reduced by more than two times compared to the highest speed of the laser spot. Full article

(This article belongs to the Special Issue Corrosion Resistance of Alloy and Coating Materials)

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14 pages, 3748 KiB

Open AccessArticle

Effect of Heat Treatment Conditions on Corrosion Resistance of 0.28C–1.4Mn–0.3Si–0.26Cr Steel with Nb, Ti, and V Microadditions

by Anna Wojtacha, Monika Kciuk and Marek Opiela

Materials 2021, 14(12), 3254; https://doi.org/10.3390/ma14123254 - 12 Jun 2021

Cited by 4 | Viewed by 2323

Abstract

The article presents the results of the research on the influence of heat treatment conditions on corrosion resistance of newly developed HSLA-type (High Strength Low Alloy) steel in selected corrosive environments. Laboratory tests were carried out with using a salt spray chamber, enabling [...] Read more.

The article presents the results of the research on the influence of heat treatment conditions on corrosion resistance of newly developed HSLA-type (High Strength Low Alloy) steel in selected corrosive environments. Laboratory tests were carried out with using a salt spray chamber, enabling the continuous spraying of brine mist (5% NaCl) during 96 h under high humidity conditions. Additionally, as part of corrosion experiments, tests were carried out using the gravimetric method, in which the intensity of corrosive processes was measured by the linear corrosion rate. The research conducted revealed that the best corrosion resistance was noted for steel with a high-temperature tempered martensite microstructure. Investigated 0.28C–1.4Mn–0.3Si–0.26Cr steel with Nb, Ti, and V microadditions can be used in offshore drilling constructions and production platforms exposed to salts present in sea water, chlorides, sulfates, carbonates, and bromides, among others. Full article

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17 pages, 5156 KiB

Open AccessArticle

The Effect of Zn and Zn–WO₃ Composites Nano-Coatings Deposition on Hardness and Corrosion Resistance in Steel Substrate

by Channagiri Mohankumar Praveen Kumar, Manjunath Patel Gowdru Chandrashekarappa, Raviraj Mahabaleshwar Kulkarni, Danil Yurievich Pimenov and Khaled Giasin

Materials 2021, 14(9), 2253; https://doi.org/10.3390/ma14092253 - 27 Apr 2021

Cited by 21 | Viewed by 3466

Abstract

Pure Zn (Zinc) and its Zn–WO₃ (Zinc–Tungsten trioxide) composite coatings were deposited on mild steel specimens by applying the electrodeposition technique. Zn–WO₃ composites were prepared for the concentration of 0.5 and 1.0 g/L of particles. The influence of WO₃ particles [...] Read more.

Pure Zn (Zinc) and its Zn–WO₃ (Zinc–Tungsten trioxide) composite coatings were deposited on mild steel specimens by applying the electrodeposition technique. Zn–WO₃ composites were prepared for the concentration of 0.5 and 1.0 g/L of particles. The influence of WO₃ particles on Zn deposition, the surface morphology of composite, and texture co-efficient were analyzed using a variety of techniques, such as X-ray diffraction (XRD) and scanning electron microscopy (SEM) with Energy Dispersive X-ray analysis (EDX). Higher corrosion resistance and microhardness were observed on the Zn–WO₃ composite (concentration of 1.0 g/L). The higher corrosion resistance and microhardness of 1.0 g/L Zn–WO₃ nanocomposite coatings effectively protect the steel used for the manufacture of products, parts, or systems from chemical or electrochemical deterioration in industrial and marine ambient environments. Full article

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9 pages, 1729 KiB

Open AccessArticle

Corrosion Protective Film Formation on Mg Alloy AZ31 by Exposure to Dilute Selenite Solutions

by Zhiyuan Feng, Charles C. Xu, Dadi Zhang and Rudolph Buchheit

Materials 2021, 14(2), 286; https://doi.org/10.3390/ma14020286 - 8 Jan 2021

Cited by 10 | Viewed by 2169

Abstract

The study of protective film formation on Mg alloys by exposure to sodium selenite solutions was conducted. Anodic polarization studies, electrochemical impedance spectroscopy studies, morphological analysis, and Energy-dispersive X-ray spectroscopy were performed on AZ31 Mg alloy after coating treatment in different concentrations of [...] Read more.

The study of protective film formation on Mg alloys by exposure to sodium selenite solutions was conducted. Anodic polarization studies, electrochemical impedance spectroscopy studies, morphological analysis, and Energy-dispersive X-ray spectroscopy were performed on AZ31 Mg alloy after coating treatment in different concentrations of sodium selenite. The corrosion resistance was improved by around 5 times compared with control. Improved resistance to localized corrosion was observed in the coatings treated by 5 mM or 10 mM sodium selenite. The protection mechanism was ascribed to the transformation of selenite to insoluble selenium, the formation of insoluble MgSeO₃ hydrate, and polymerization of amorphous selenium. Full article

(This article belongs to the Special Issue Corrosion Resistance of Alloy and Coating Materials)

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19 pages, 6420 KiB

Open AccessEditor’s ChoiceArticle

The Influence of ZnO Oxide Layer on the Physicochemical Behavior of Ti6Al4V Titanium Alloy

by Anna Woźniak, Witold Walke, Agata Jakóbik-Kolon, Bogusław Ziębowicz, Zbigniew Brytan and Marcin Adamiak

Materials 2021, 14(1), 230; https://doi.org/10.3390/ma14010230 - 5 Jan 2021

Cited by 16 | Viewed by 4032

Abstract

Titanium and its alloys are characterized by high biocompatibility and good corrosion resistance as a result of the ability to form a TiO₂ oxide layer. However, based on literature data it can be concluded that titanium degradation products, in the form of [...] Read more.

Titanium and its alloys are characterized by high biocompatibility and good corrosion resistance as a result of the ability to form a TiO₂ oxide layer. However, based on literature data it can be concluded that titanium degradation products, in the form of titanium particles, metal-protein groups, oxides and ions, may cause allergic, inflammatory reactions and bone resorption. The corrosion process of Ti6Al4V in the human body environment may be intensified by a decreased pH and concentration of chloride compounds. The purpose of this article was to analyze the corrosion resistance of the Ti6Al4V alloy, obtained by the selective laser melting method in a corrosion solution of neutral pH and in a solution simulating peri-implant inflammatory conditions. Additionally, the influence of zinc oxide deposited by the atomic layer deposition method on the improvement of the physicochemical behavior of the Ti6Al4V alloy was analyzed. In order to characterize the ZnO layer, tests of chemical and phase composition as well as surface morphology investigation were performed. As part of the assessment of the physicochemical properties of the uncoated samples and those with the ZnO layer, tests of wetting angle, pitting corrosion and impedance corrosion were carried out. The number of ions released after the potentiodynamic test were measured using the inductively coupled plasma atomic emission spectrometry (ICP–AES) method. It can be concluded that samples after surface modification (with the ZnO layer) were characterized by favorable physicochemical properties and had higher corrosion resistance. Full article

(This article belongs to the Special Issue Corrosion Resistance of Alloy and Coating Materials)

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19 pages, 7298 KiB

Open AccessArticle

Effects of Different Surface Native Pre-Oxides on the Hot Corrosion Properties of Nickel-Based Single Crystal Superalloys

by Zehao Chen, Shusuo Li, Mengmeng Wu, Yanling Pei, Shengkai Gong and Heng Zhang

Materials 2020, 13(24), 5774; https://doi.org/10.3390/ma13245774 - 17 Dec 2020

Cited by 5 | Viewed by 2301

Abstract

A study is carried out on the effect of different surface native pre-oxides on hot corrosion of single crystal nickel-based superalloy at 900 °C. The effect of different oxides formed by different superalloys through pre-oxidation on hot corrosion is verified by normal hot [...] Read more.

A study is carried out on the effect of different surface native pre-oxides on hot corrosion of single crystal nickel-based superalloy at 900 °C. The effect of different oxides formed by different superalloys through pre-oxidation on hot corrosion is verified by normal hot corrosion and tube sealing experiments. The relationship between different surface oxides and the effect of different surface oxides layer on the hot corrosion properties of alloys are studied. In summary, the stable and dense surface pre-Al₂O₃ layer which can be obtained by pre-oxidation has an obvious positive effect on the improvement of superalloy hot corrosion resistance in reaction. In addition, the internal sulfides are analyzed in depth, and the relationship between Cr, Mo, O and S is discussed in detail. Full article

(This article belongs to the Special Issue Corrosion Resistance of Alloy and Coating Materials)

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