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10 pages, 6962 KiB

Open AccessArticle

Effect of Spraying Power on Oxidation Resistance of MoSi₂-ZrB₂ Coating for Nb-Si Based Alloy Prepared by Atmospheric Plasma

by Guanqun Zhuo, Linfen Su, Kaiyong Jiang and Jianyong Yang

Materials 2020, 13(22), 5060; https://doi.org/10.3390/ma13225060 - 10 Nov 2020

Cited by 7 | Viewed by 1640

Abstract

The MoSi₂-ZrB₂ coatings were prepared on Nb-Si based alloy by atmospheric plasma spraying with the spraying power 40, 43 and 45 kW. The effect of spraying power on the microstructure and oxidation resistance of MoSi₂-ZrB₂ coating at [...] Read more.

The MoSi₂-ZrB₂ coatings were prepared on Nb-Si based alloy by atmospheric plasma spraying with the spraying power 40, 43 and 45 kW. The effect of spraying power on the microstructure and oxidation resistance of MoSi₂-ZrB₂ coating at 1250 °C were studied. The results showed that the main constituent phases of coatings were MoSi₂ at all spraying power. The coating became more compact as the spraying power increased. The coating prepared at 45 kW was dense and uniform, which exhibited the best oxidation resistance due to the formation of a dense and uniform glass layer consisting of SiO₂ and ZrSiO₄. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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16 pages, 6101 KiB

Open AccessArticle

Corrosion of High-Strength Steel Wires under Tensile Stress

by Shanglin Lv, Kefei Li, Jie Chen and Xiaobin Li

Materials 2020, 13(21), 4790; https://doi.org/10.3390/ma13214790 - 27 Oct 2020

Cited by 4 | Viewed by 2169

Abstract

The stress corrosion cracking is the central issue for high-strength wires under high tensile stress used in civil engineering. This paper explores the resistance of stress corrosion cracking of three typical steel wires of high-strength carbon through a laboratory test, combining the actions [...] Read more.

The stress corrosion cracking is the central issue for high-strength wires under high tensile stress used in civil engineering. This paper explores the resistance of stress corrosion cracking of three typical steel wires of high-strength carbon through a laboratory test, combining the actions of tensile stress and corrosive solution. Besides, the impact of tensile stress and immersion time are also investigated. During the tests, the wires were subject to electrochemical measurements of potentiodynamic polarization and electrochemical impedance spectroscopy, and the microstructure analysis was performed on the fractured cross sections. The obtained results show the following: the high-strength wire, conforming to GB/T 5224, has higher resistance to the combined actions of tensile stress and corrosive solution; tensile stress of 70% fracture strength and longer loading-immersion time make the film of corrosion products on steel surface unstable and weaken the corrosion resistance; the surface film consisted of the iron oxide film and the corrosion products film whose components are mainly iron thiocyanate and iron sulphide. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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17 pages, 55800 KiB

Open AccessArticle

Effects of Alloying Elements (C, Mo) on Hydrogen Assisted Cracking Behaviors of A516-65 Steels in Sour Environments

by Jin Sung Park, Jin Woo Lee, Joong Ki Hwang and Sung Jin Kim

Materials 2020, 13(18), 4188; https://doi.org/10.3390/ma13184188 - 21 Sep 2020

Cited by 10 | Viewed by 2553

Abstract

This study examined the effects of alloying elements (C, Mo) on hydrogen-induced cracking (HIC) and sulfide stress cracking (SSC) behaviors of A516-65 grade pressure vessel steel in sour environments. A range of experimental and analytical methods of HIC, SSC, electrochemical permeation, and immersion [...] Read more.

This study examined the effects of alloying elements (C, Mo) on hydrogen-induced cracking (HIC) and sulfide stress cracking (SSC) behaviors of A516-65 grade pressure vessel steel in sour environments. A range of experimental and analytical methods of HIC, SSC, electrochemical permeation, and immersion experiments were used. The steel with a higher C content had a larger fraction of banded pearlite, which acted as a reversible trap for hydrogen, and slower diffusion kinetics of hydrogen was obtained. In addition, a higher hardness in the mid-thickness regions of the steel, due to center segregation, resulted in easier HIC propagation. On the other hand, the steel with a higher Mo content showed more dispersed banded pearlite and a larger amount of irreversibly trapped hydrogen. Nevertheless, the addition of Mo to the steel can deteriorate the surface properties through localized pitting and the local detachment of corrosion products with uneven interfaces, increasing the vulnerability to SSC. The mechanistic reasons for the results are discussed, and a desirable alloy design for ensuring an enhanced resistance to hydrogen assisted cracking (HAC) is proposed. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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15 pages, 5548 KiB

Open AccessArticle

Effects of the Combined Addition of Zn and Mg on Corrosion Behaviors of Electropainted AlSi-Based Metallic Coatings Used for Hot-Stamping Steel Sheets

by Si On Kim, Won Seog Yang and Sung Jin Kim

Materials 2020, 13(15), 3379; https://doi.org/10.3390/ma13153379 - 30 Jul 2020

Cited by 4 | Viewed by 2281

Abstract

The effects of the combined addition of Zn and Mg on the corrosion resistance of AlSi-based coating for automotive steel sheets were investigated using a variety of analytical and electrochemical techniques. The preferential dissolution of Mg and Zn from MgZn₂/Mg₂ [...] Read more.

The effects of the combined addition of Zn and Mg on the corrosion resistance of AlSi-based coating for automotive steel sheets were investigated using a variety of analytical and electrochemical techniques. The preferential dissolution of Mg and Zn from MgZn₂/Mg₂Si phases occurred on the AlSi-based coating that had been alloyed with a smaller portion of Zn and Mg, which contributed to the rapid surface coverage by corrosion products with a protective nature, reducing the corrosion current density. On the other hand, localized corrosion attacks caused by the selective dissolution of Mg were also observed in the AlSi-based coating with a smaller portion of Zn and Mg. Such alloying can also worsen its corrosion resistance when coated additionally with electrodeposited paint. The mechanistic reasons for these conflicting results are also discussed. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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18 pages, 5617 KiB

Open AccessArticle

Effects of Different Ions and Temperature on Corrosion Behavior of Pure Iron in Anoxic Simulated Groundwater

by Teng Li, Guokai Huang, Yanpeng Feng, Miao Yang, Lingyu Wang, Daqing Cui and Xian Zhang

Materials 2020, 13(12), 2713; https://doi.org/10.3390/ma13122713 - 15 Jun 2020

Cited by 9 | Viewed by 2416

Abstract

As a typical material of the insert in high-level radioactive waste (HLW) geological disposal canisters, iron-based materials will directly contact with groundwater after the failure of a metallic canister, acting as a chemical barrier to prevent HLW leaking into groundwater. In this paper, [...] Read more.

As a typical material of the insert in high-level radioactive waste (HLW) geological disposal canisters, iron-based materials will directly contact with groundwater after the failure of a metallic canister, acting as a chemical barrier to prevent HLW leaking into groundwater. In this paper, anoxic groundwater was simulated by mixing 10 mM NaCl and 2 mM NaHCO₃ purged by Ar gas (containing 0.3% CO₂) with different added ions (Ca²⁺, CO₃²⁻ and SiO₃²⁻) and operation temperatures (25, 40 and 60 °C). An electrochemical measurement, immersion tests and surface characterization were carried out to study the corrosion behavior of pure iron in the simulated groundwater. The effects of Ca²⁺ on the corrosion behavior of iron is negligible, however, Cl⁻ plays an important role in accelerating the corrosion activity with the increased concentration and temperature. With increased concentrations of CO₃²⁻ and SiO₃²⁻, the corrosion resistance of iron is largely improved, which is attributed to the formation of a uniform passivation film. The independent effects of temperature on the corrosion behavior of iron are resulted from the repeated passivation–dissolution processes in the formation of the passivation film, resulting from the synergistic effects of CO₃²⁻/SiO₃²⁻ and Cl⁻. The formation of ferric silicate is dominant in the passivation film with the addition of SiO₃²⁻, which effectively protects the iron surface from corrosion. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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17 pages, 15277 KiB

Open AccessArticle

Effect of Load on the Corrosion Behavior of Friction Stir Welded AA 7075-T6 Aluminum Alloy

by Marina Cabrini, Sara Bocchi, Gianluca D’Urso, Claudio Giardini, Sergio Lorenzi, Cristian Testa and Tommaso Pastore

Materials 2020, 13(11), 2600; https://doi.org/10.3390/ma13112600 - 07 Jun 2020

Cited by 6 | Viewed by 2479

Abstract

The paper focuses on the corrosion behavior of aluminum joints made by friction stir welding as a function of loading conditions. A four-points bend-beam test, constant loading test, and slow strain-rate test were carried out on AA 7075-T6 alloy in aerated NaCl 35g/L [...] Read more.

The paper focuses on the corrosion behavior of aluminum joints made by friction stir welding as a function of loading conditions. A four-points bend-beam test, constant loading test, and slow strain-rate test were carried out on AA 7075-T6 alloy in aerated NaCl 35g/L solution at room temperature monitoring the free corrosion potential. The penetration depth of the intergranular attack was deeper after the four-point bent-beam tests compared to all the other testing techniques. Preferential dissolution along the grain boundaries was found in the heat-affected zone and the attack follows the elongated grains structure along the rolling direction. However, no stress-corrosion cracking phenomena were detected. No relevant stress corrosion cracking (SCC) crack embryos propagation was noticed under uniaxial tensile tests—both constant loading and slow strain-rate tests—manly due to the high dissolution rate occurring at the crack tip which promoted premature shear ruptures. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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17 pages, 12405 KiB

Open AccessArticle

Chitosan/Lignosulfonate Nanospheres as “Green” Biocide for Controlling the Microbiologically Influenced Corrosion of Carbon Steel

by Pathath Abdul Rasheed, Ravi P. Pandey, Khadeeja A. Jabbar, Ayman Samara, Aboubakr M. Abdullah and Khaled A. Mahmoud

Materials 2020, 13(11), 2484; https://doi.org/10.3390/ma13112484 - 29 May 2020

Cited by 14 | Viewed by 2796

Abstract

In this work, uniform cross-linked chitosan/lignosulfonate (CS/LS) nanospheres with an average diameter of 150–200 nm have been successfully used as a novel, environmentally friendly biocide for the inhibition of mixed sulfate-reducing bacteria (SRB) culture, thereby controlling microbiologically influenced corrosion (MIC) on carbon steel. [...] Read more.

In this work, uniform cross-linked chitosan/lignosulfonate (CS/LS) nanospheres with an average diameter of 150–200 nm have been successfully used as a novel, environmentally friendly biocide for the inhibition of mixed sulfate-reducing bacteria (SRB) culture, thereby controlling microbiologically influenced corrosion (MIC) on carbon steel. It was found that 500 µg·mL⁻¹ of the CS/LS nanospheres can be used efficiently for the inhibition of SRB-induced corrosion up to a maximum of 85% indicated by a two fold increase of charge transfer resistance (R_ct) on the carbon steel coupons. The hydrophilic surface of CS/LS can readily bind to the negatively charged bacterial surfaces and thereby leads to the inactivation or damage of bacterial cells. In addition, the film formation ability of chitosan on the coupon surface may have formed a protective layer to prevent the biofilm formation by hindering the initial bacterial attachment, thus leading to the reduction of corrosion. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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17 pages, 8708 KiB

Open AccessArticle

Effect of Cast Defects on the Corrosion Behavior and Mechanism of UNS C95810 Alloy in Artificial Seawater

by Xu Zhao, Yuhong Qi, Jintao Wang, Zhanping Zhang, Jing Zhu, Linlin Quan and Dachuan He

Materials 2020, 13(7), 1790; https://doi.org/10.3390/ma13071790 - 10 Apr 2020

Cited by 6 | Viewed by 2413

Abstract

To study the effect of cast defects on the corrosion behavior and mechanism of the UNS C95810 alloy in seawater, an investigation was conducted by weight loss determination, scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), X-ray diffraction (XRD) and electrochemical testing [...] Read more.

To study the effect of cast defects on the corrosion behavior and mechanism of the UNS C95810 alloy in seawater, an investigation was conducted by weight loss determination, scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), X-ray diffraction (XRD) and electrochemical testing of the specimen with and without cast defects on the surface. The results show that the corrosion rate of the alloy with cast defects is higher than that of the alloy without cast defects, but the defects do not change the composition of the resulting corrosion products. The defects increase the complexity of the alloy microstructure and the tendency toward galvanic corrosion, which reduce the corrosion potential from −3.83 to −86.31 mV and increase the corrosion current density from 0.228 to 0.23 μA⋅cm⁻². Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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15 pages, 8188 KiB

Open AccessArticle

Effect of Cooling Rate at the Eutectoid Transformation Temperature on the Corrosion Resistance of Zn-4Al Alloy

by Marzena M. Lachowicz and Robert Jasionowski

Materials 2020, 13(7), 1703; https://doi.org/10.3390/ma13071703 - 05 Apr 2020

Cited by 5 | Viewed by 2178

Abstract

The main purpose of this work was to experimentally determine the effect of the cooling rate during the eutectoid transformation on the corrosion resistance of a hypoeutectic Zn-4Al cast alloy in 5% NaCl solution. This was considered in relation to the alloy microstructure. [...] Read more.

The main purpose of this work was to experimentally determine the effect of the cooling rate during the eutectoid transformation on the corrosion resistance of a hypoeutectic Zn-4Al cast alloy in 5% NaCl solution. This was considered in relation to the alloy microstructure. For this purpose, metallographic and electrochemical studies were performed. It was found that the faster cooling promoted the formation of finer (α + η) eutectoid structures, which translated into a higher hardness and lower corrosion current density. In the initial stage of corrosion processes the eutectoid structure in the eutectic areas were attacked. At the further stages of corrosion development, the phase η was dissolved, and the α phase appears to be protected by the formation of corrosion products. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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15 pages, 4002 KiB

Open AccessArticle

Determination of Plate Corrosion Dimension Using Nd:YAG Pulsed Laser-generated Wavefield and Experimental Dispersion Curves

by Kassahun Demissie Tola, Dai Quoc Tran, Byoungjoon Yu and Seunghee Park

Materials 2020, 13(6), 1436; https://doi.org/10.3390/ma13061436 - 21 Mar 2020

Cited by 4 | Viewed by 1986

Abstract

Corrosion detection using a pulsed laser scanning system can be performed via ultrasonic wave propagation imaging. This method outputs illustrations of the wave field within the host structure; thus, it can depict wave–corrosion area interactions. Additionally, post-processing can be performed to enhance the [...] Read more.

Corrosion detection using a pulsed laser scanning system can be performed via ultrasonic wave propagation imaging. This method outputs illustrations of the wave field within the host structure; thus, it can depict wave–corrosion area interactions. Additionally, post-processing can be performed to enhance the visualization of corroded areas. The wavefield energy computed using RMS (Root Mean Square) is a validated post-processing tool capable of displaying the location and area of corrosion-damaged regions. Nonetheless, to characterize corrosion, it is necessary to determine its depth. The measurement of depth in conjunction with that of the corroded area via the RMS distribution enables the determination of all dimensions of corrosion damage. Thereafter, the flaw severity can be evaluated. This study employed a wavefield within a plate on which corrosion was developed artificially to generate frequency–wavenumber dispersion curves. The curves were compared with their counterparts from a corrosion-free plate. Alternatively, they could be compared with dispersion curves drawn using the depth and material properties of a pristine plate via a computer program. Frequency–wavenumber pairs were extracted from the dispersion curves produced using the portion of the wavefield within the corroded area. These were inserted into the Rayleigh–Lamb equation, from which depths were calculated and averaged. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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13 pages, 3088 KiB

Open AccessArticle

Investigation of Biogenic Passivating Layers on Corroded Iron

by Lucrezia Comensoli, Monica Albini, Wafa Kooli, Julien Maillard, Tiziana Lombardo, Pilar Junier and Edith Joseph

Materials 2020, 13(5), 1176; https://doi.org/10.3390/ma13051176 - 06 Mar 2020

Cited by 7 | Viewed by 2397

Abstract

This study evaluates mechanisms of biogenic mineral formation induced by bacterial iron reduction for the stabilization of corroded iron. As an example, the Desulfitobacterium hafniense strain TCE1 was employed to treat corroded coupons presenting urban natural atmospheric corrosion, and spectroscopic investigations were performed [...] Read more.

This study evaluates mechanisms of biogenic mineral formation induced by bacterial iron reduction for the stabilization of corroded iron. As an example, the Desulfitobacterium hafniense strain TCE1 was employed to treat corroded coupons presenting urban natural atmospheric corrosion, and spectroscopic investigations were performed on the samples’ cross-sections to evaluate the corrosion stratigraphy. The treated samples presented a protective continuous layer of iron phosphates (vivianite Fe²⁺₃(PO₄)₂·8H₂O and barbosalite Fe²⁺Fe³⁺₂(PO₄)₂(OH)₂), which covered 92% of the surface and was associated with a decrease in the thickness of the original corrosion layer. The results allow us to better understand the conversion of reactive corrosion products into stable biogenic minerals, as well as to identify important criteria for the design of a green alternative treatment for the stabilization of corroded iron. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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11 pages, 3307 KiB

Open AccessArticle

Corrosion Resistance of Heat-Treated Ni-W Alloy Coatings

by Magdalena Popczyk, Julian Kubisztal, Andrzej Szymon Swinarew, Zbigniew Waśkiewicz, Arkadiusz Stanula and Beat Knechtle

Materials 2020, 13(5), 1172; https://doi.org/10.3390/ma13051172 - 06 Mar 2020

Cited by 20 | Viewed by 2907

Abstract

The paper presents research on evaluation of corrosion resistance of Ni-W alloy coatings subjected to heat treatment. The corrosion resistance was tested in 5% NaCl solution by the use of potentiodynamic polarization technique and electrochemical impedance spectroscopy. Characteristics of the Ni-W coatings after [...] Read more.

The paper presents research on evaluation of corrosion resistance of Ni-W alloy coatings subjected to heat treatment. The corrosion resistance was tested in 5% NaCl solution by the use of potentiodynamic polarization technique and electrochemical impedance spectroscopy. Characteristics of the Ni-W coatings after heat treatment were carried out using scanning electron microscopy, scanning Kelvin probe technique and X-ray diffraction. Suggested reasons for the improvement of properties of the heat treated Ni-W coating, obtained at the lowest current density value (125 mA∙cm⁻²), are the highest tungsten content (c.a. 25 at.%) as well as the smallest and the most homogeneous electrochemically active surface area. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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20 pages, 1424 KiB

Open AccessArticle

Kinetic Model of Incipient Hydride Formation in Zr Clad under Dynamic Oxide Growth Conditions

by Qianran Yu, Michael Reyes, Nachiket Shah and Jaime Marian

Materials 2020, 13(5), 1088; https://doi.org/10.3390/ma13051088 - 29 Feb 2020

Cited by 8 | Viewed by 2480

Abstract

The formation of elongated zirconium hydride platelets during corrosion of nuclear fuel clad is linked to its premature failure due to embrittlement and delayed hydride cracking. Despite their importance, however, most existing models of hydride nucleation and growth in Zr alloys are phenomenological [...] Read more.

The formation of elongated zirconium hydride platelets during corrosion of nuclear fuel clad is linked to its premature failure due to embrittlement and delayed hydride cracking. Despite their importance, however, most existing models of hydride nucleation and growth in Zr alloys are phenomenological and lack sufficient physical detail to become predictive under the variety of conditions found in nuclear reactors during operation. Moreover, most models ignore the dynamic nature of clad oxidation, which requires that hydrogen transport and precipitation be considered in a scenario where the oxide layer is continuously growing at the expense of the metal substrate. In this paper, we perform simulations of hydride formation in Zr clads with a moving oxide/metal boundary using a stochastic kinetic diffusion/reaction model parameterized with state-of-the-art defect and solute energetics. Our model uses the solutions of the hydrogen diffusion problem across an increasingly-coarse oxide layer to define boundary conditions for the kinetic simulations of hydrogen penetration, precipitation, and dissolution in the metal clad. Our method captures the spatial dependence of the problem by discretizing all spatial derivatives using a stochastic finite difference scheme. Our results include hydride number densities and size distributions along the radial coordinate of the clad for the first 1.6 h of evolution, providing a quantitative picture of hydride incipient nucleation and growth under clad service conditions. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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23 pages, 15951 KiB

Open AccessArticle

Biofilm Formation Plays a Crucial Rule in the Initial Step of Carbon Steel Corrosion in Air and Water Environments

by Akiko Ogawa, Keito Takakura, Nobumitsu Hirai, Hideyuki Kanematsu, Daisuke Kuroda, Takeshi Kougo, Katsuhiko Sano and Satoshi Terada

Materials 2020, 13(4), 923; https://doi.org/10.3390/ma13040923 - 19 Feb 2020

Cited by 25 | Viewed by 3081

Abstract

In this study, we examined the relationship between the effect of a zinc coating on protecting carbon steel against biofilm formation in both air and water environments. SS400 carbon steel coupons were covered with a zinc thermal spray coating or copper thermal spray [...] Read more.

In this study, we examined the relationship between the effect of a zinc coating on protecting carbon steel against biofilm formation in both air and water environments. SS400 carbon steel coupons were covered with a zinc thermal spray coating or copper thermal spray coating. Coated coupons were exposed to either air or water conditions. Following exposure, the surface conditions of each coupon were observed using optical microscopy, and quantitatively analyzed using an x-ray fluorescence analyzer. Debris on the surface of the coupons was used for biofilm analysis including crystal violet staining for quantification, Raman spectroscopic analysis for qualification, and microbiome analysis. The results showed that the zinc thermal spray coating significantly inhibited iron corrosion as well as biofilm formation in both air and water environments. The copper thermal spray coating, however, accelerated iron corrosion in both air and water environments, but accelerated biofilm formation only in a water environment. microbially-influenced-corrosion-related bacteria were barely detected on any coupons, whereas biofilms were detected on all coupons. To summarize these results, electrochemical corrosion is dominant in an air environment and microbially influenced corrosion is strongly involved in water corrosion. Additionally, biofilm formation plays a crucial rule in carbon steel corrosion in both air and water, even though microbially-influenced-corrosion-related bacteria are barely involved in this corrosion. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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15 pages, 16376 KiB

Open AccessArticle

On the Influence of Corrosion on the Load-Carrying Capacity of Old Riveted Bridges

by Jozef Gocál and Jaroslav Odrobiňák

Materials 2020, 13(3), 717; https://doi.org/10.3390/ma13030717 - 05 Feb 2020

Cited by 19 | Viewed by 2207

Abstract

Steel corrosion is one of the most dominant factors in the degradation of transport infrastructure. This article deals with the impact of the atmospheric corrosion of structural steel on the load-carrying capacity of old riveted bridge structures. A study on the impact of [...] Read more.

Steel corrosion is one of the most dominant factors in the degradation of transport infrastructure. This article deals with the impact of the atmospheric corrosion of structural steel on the load-carrying capacity of old riveted bridge structures. A study on the impact of corrosion losses on the resistance and, thus, the load-carrying capacity of eight chosen bridge members with riveted I-sections from three different bridge substructures is presented. The load-carrying capacity calculation is carried out using modern procedures and on the basis of the diagnosed state of the structural elements. Within the analysis of the results, the need for long-term in situ corrosion measurements, as well as the need for regular inspections on the existing bridges are also discussed. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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13 pages, 3402 KiB

Open AccessArticle

Crystallographic Evaluation of Susceptibility to Intergranular Corrosion in Austenitic Stainless Steel with Various Degrees of Sensitization

by Tomoyuki Fujii, Takaya Furumoto, Keiichiro Tohgo and Yoshinobu Shimamura

Materials 2020, 13(3), 613; https://doi.org/10.3390/ma13030613 - 30 Jan 2020

Cited by 13 | Viewed by 2752

Abstract

This study investigated the susceptibility to intergranular corrosion (IGC) in austenitic stainless steel with various degrees of sensitization (DOSs) from a microstructural viewpoint based on the coincidence site lattice (CSL) model. IGC testing was conducted using oxalic acid and type 304 stainless steel [...] Read more.

This study investigated the susceptibility to intergranular corrosion (IGC) in austenitic stainless steel with various degrees of sensitization (DOSs) from a microstructural viewpoint based on the coincidence site lattice (CSL) model. IGC testing was conducted using oxalic acid and type 304 stainless steel specimens with electrochemical potentiokinetic reactivation (EPR) ratios that varied from 3 to 30%. As a measure of IGC susceptibility, the width of the corroded groove was used. The relationship between IGC susceptibility, grain boundaries (GB) structure, and EPR ratio of the specimens was evaluated. As a result, the IGC susceptibility cannot be characterized using the Σ value, irrespective of the DOS of the specimen. The IGC susceptibility increases with increasing unit cell area of CSL boundaries, which is a measure of the stability of the CSL boundaries, and then levels off. The relationship between the IGC susceptibility and unit cell area is sigmoidal, irrespective of the DOS of the specimen. The sigmoid curve shifts rightward and the upper bound of IGC susceptibility decreases with decreasing DOS of the specimen. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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14 pages, 5351 KiB

Open AccessArticle

Magnetic, Magnetoelastic and Corrosion Resistant Properties of (Fe–Ni)-Based Metallic Glasses for Structural Health Monitoring Applications

by Ariane Sagasti, Verónica Palomares, Jose María Porro, Iñaki Orúe, M. Belén Sánchez-Ilárduya, Ana Catarina Lopes and Jon Gutiérrez

Materials 2020, 13(1), 57; https://doi.org/10.3390/ma13010057 - 20 Dec 2019

Cited by 13 | Viewed by 2513

Abstract

We have performed a study of the magnetic, magnetoelastic, and corrosion resistance properties of seven different composition magnetoelastic-resonant platforms. For some applications, such as structural health monitoring, these materials must have not only good magnetomechanical properties, but also a high corrosion resistance. In [...] Read more.

We have performed a study of the magnetic, magnetoelastic, and corrosion resistance properties of seven different composition magnetoelastic-resonant platforms. For some applications, such as structural health monitoring, these materials must have not only good magnetomechanical properties, but also a high corrosion resistance. In the fabricated metallic glasses of composition

{Fe}_{73 - x} {Ni}_{x} {Cr}_{5} {Si}_{10} B_{12}

, the Fe/Ni ratio was varied (Fe + Ni = 73% at.) thus changing the magnetic and magnetoelastic properties. A small amount of chromium

({Cr}_{5})

was added in order to achieve the desired good corrosion resistance. As expected, all the studied properties change with the composition of the samples. Alloys containing a higher amount of

Ni

than

Fe

do not show magnetic behavior at room temperature, while iron-rich alloys have demonstrated not only good magnetic properties, but also good magnetoelastic ones, with magnetoelastic coupling coefficient as high as

0.41

for

x = 0

in the

{Fe}_{73} {Ni}_{0} {Cr}_{5} {Si}_{10} B_{12}

(the sample containing only

Fe

but not

Ni

). Concerning corrosion resistance, we have found a continuous degradation of these properties as the

Ni

content increases in the composition. Thus, the corrosion potential decreases monotonously from 46.74 mV for the

x = 0

, composition

{Fe}_{73} {Ni}_{0} {Cr}_{5} {Si}_{10} B_{12}

to −239.47 mV for the

x = 73

, composition

{Fe}_{0} {Ni}_{73} {Cr}_{5} {Si}_{10} B_{12}

. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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16 pages, 7977 KiB

Open AccessArticle

The Characterization of Stress Corrosion Cracking in the AE44 Magnesium Casting Alloy Using Quantitative Fractography Methods

by Maria Sozańska, Adrian Mościcki and Tomasz Czujko

Materials 2019, 12(24), 4125; https://doi.org/10.3390/ma12244125 - 09 Dec 2019

Cited by 6 | Viewed by 2695

Abstract

In this work an assessment of the susceptibility of the AE44 magnesium alloy to stress corrosion cracking in a 0.1M Na₂SO₄ environment is presented. The basic assumed criterion for assessing the alloy behavior under complex mechanical and corrosive loads is [...] Read more.

In this work an assessment of the susceptibility of the AE44 magnesium alloy to stress corrosion cracking in a 0.1M Na₂SO₄ environment is presented. The basic assumed criterion for assessing the alloy behavior under complex mechanical and corrosive loads is deterioration in mechanical properties (elongation, reduction in area, tensile strength and time to failure). The AE44 magnesium alloy was subjected to the slow strain rate test (SSR) in air and in a corrosive environment under open circuit potential (OCP) conditions. In each variant, the content of hydrogen in the alloy was determined. The obtained fractures were subjected to a quantitative evaluation by original fractography methods. It was found that under stress corrosion cracking (SCC) conditions and in the presence of hydrogen the mechanical properties of AE44 deteriorated. The change in the mechanical properties under SCC conditions in a corrosive environment was accompanied by the presence of numerous cracks, both on fracture surfaces and in the alloy microstructure. The developed method for the quantitative evaluation of cracks on the fracture surface turned out to be a more sensitive method, enabling the assessment of the susceptibility of AE44 under complex mechanical and corrosive loads in comparison with deterioration in mechanical properties. Mechanical tests showed a decrease in properties after SSRT tests in corrosive environments (UTS ≈ 153 MPa, ε = 11.2%, Z = 4.0%) compared to the properties after air tests (UTS ≈ 166 MPa, ε = 11.9%, Z = 7.8%) but it was not as visible as the results of quantitative assessment of cracks at fractures (number of cracks, length of cracks): after tests in corrosive environment (900; 21.3 μm), after tests in air (141; 34.5 μm). These results indicate that the proposed new proprietary test methodology can be used to quantify the SSC phenomenon in cases of slight changes in mechanical properties after SSRT tests in a corrosive environment in relation to the test results in air. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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12 pages, 3986 KiB

Open AccessArticle

The Effect of Nb-Content on the Microstructures and Corrosion Properties of CrFeCoNiNb_x High-Entropy Alloys

by Chun-Huei Tsau, Chen-Yu Yeh and Meng-Chi Tsai

Materials 2019, 12(22), 3716; https://doi.org/10.3390/ma12223716 - 11 Nov 2019

Cited by 18 | Viewed by 2460

Abstract

This work studied the effect of niobium-content on the microstructures, hardness, and corrosion properties of CrFeCoNiNb_x alloys. Results indicated that the microstructures of these alloys changed from granular structures (CrFeCoNi alloy) to the hypereutectic structures (CrFeCoNiNb_0.2 and CrFeCoNi_0.4 alloys), and [...] Read more.

This work studied the effect of niobium-content on the microstructures, hardness, and corrosion properties of CrFeCoNiNb_x alloys. Results indicated that the microstructures of these alloys changed from granular structures (CrFeCoNi alloy) to the hypereutectic structures (CrFeCoNiNb_0.2 and CrFeCoNi_0.4 alloys), and then to the hypoeutectic microstructures (CrFeCoNiNb_0.6 and CrFeCoNi alloys). The lattice constants of the major two phases in these alloys, fcc and Laves phases (hcp), increased with the increasing of Nb-content because of solid-solution strengthening. The hardness of CrFeCoNiNb_x alloys also had the same tendency. Adding niobium would slightly lessen the corrosion resistance of CrFeCoNiNb_x alloys in 1 M deaerated sulfuric acid and 1 M deaerated sodium chloride solutions, but the CrFeCoNiNb_x alloys still had better corrosion resistance in comparison with commercial 304 stainless steel. In these dual-phased CrFeCoNiNb_x alloys, the fcc phase was more severely corroded than the Laves phase after polarization tests in these two solutions. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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13 pages, 3853 KiB

Open AccessArticle

Construction of a Novel Lignin-Based Quaternary Ammonium Material with Excellent Corrosion Resistant Behavior and Its Application for Corrosion Protection

by Chao Gao, Shoujuan Wang, Xinyu Dong, Keyin Liu, Xin Zhao and Fangong Kong

Materials 2019, 12(11), 1776; https://doi.org/10.3390/ma12111776 - 31 May 2019

Cited by 15 | Viewed by 2918

Abstract

A novel lignin-based quaternary ammonium material (lignin-DMC) with excellent corrosion resistant behavior was synthesized by grafting DMC (methacrylatoethyl trimethyl ammonium chloride) onto kraft lignin. The structure and anti-corrosion performance of lignin-DMC was investigated using many methods, for instance the scanning electron microscope (SEM), [...] Read more.

A novel lignin-based quaternary ammonium material (lignin-DMC) with excellent corrosion resistant behavior was synthesized by grafting DMC (methacrylatoethyl trimethyl ammonium chloride) onto kraft lignin. The structure and anti-corrosion performance of lignin-DMC was investigated using many methods, for instance the scanning electron microscope (SEM), atomic force microscopy (AFM), charge density analysis, molecular weight analysis, electrochemical methods. Fourier-transform infrared spectroscopy (FT-IR) confirmed the formation of the lignin-DMC. The experiment results indicated that maximum corrosion inhibition efficiency (87.65%) occurred at a concentration of 75 mg/L via weight loss measurement. Polarization curves indicated that lignin-DMC was a mixed-type inhibitor with an efficient anti-corrosion performance in an acid medium. Electrochemical impedance spectroscopy (EIS) results indicated that lignin-DMC could create a shielding effectiveness and achieve a protective effectiveness in the HCl solution. Moreover, lignin-DMC displayed a physical and chemical adsorption process between 20 KJ/mol and 40 KJ/mol, which followed the Langmuir adsorption isotherm model. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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11 pages, 4274 KiB

Open AccessArticle

Microstructure and Selective Corrosion of Alloy 625 Obtained by Means of Laser Powder Bed Fusion

by Marina Cabrini, Sergio Lorenzi, Cristian Testa, Fabio Brevi, Sara Biamino, Paolo Fino, Diego Manfredi, Giulio Marchese, Flaviana Calignano and Tommaso Pastore

Materials 2019, 12(11), 1742; https://doi.org/10.3390/ma12111742 - 29 May 2019

Cited by 22 | Viewed by 3518

Abstract

The effect of microstructure on the susceptibility to selective corrosion of Alloy 625 produced by laser powder bed fusion (LPBF) process was investigated through intergranular corrosion tests according to ASTM G28 standard. The effect of heat treatment on selective corrosion susceptibility was also [...] Read more.

The effect of microstructure on the susceptibility to selective corrosion of Alloy 625 produced by laser powder bed fusion (LPBF) process was investigated through intergranular corrosion tests according to ASTM G28 standard. The effect of heat treatment on selective corrosion susceptibility was also evaluated. The behavior was compared to commercial hot-worked, heat treated Grade 1 Alloy 625. The morphology of attack after boiling ferric sulfate-sulfuric acid test according to ASTM G28 standard is less penetrating for LPBF 625 alloy compared to hot-worked and heat-treated alloy both in as-built condition and after heat treatment. The different attack morphology can be ascribed to the oversaturation of the alloying elements in the nickel austenitic matrix obtained due to the very high cooling rate. On as-built specimens, a shallow selective attack of the border of the melt pools was observed, which disappeared after the heat treatment. The results confirmed similar intergranular corrosion susceptibility, but different corrosion morphologies were detected. The results are discussed in relation to the unique microstructures of LPBF manufactured alloys. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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11 pages, 1175 KiB

Open AccessArticle

Hydrogen Accumulation and Distribution in Pipeline Steel in Intensified Corrosion Conditions

by Anatolii I. Titov, Aleksandr V. Lun-Fu, Aleksandr V. Gayvaronskiy, Mikhail A. Bubenchikov, Aleksei M. Bubenchikov, Andrey M. Lider, Maxim S. Syrtanov and Viktor N. Kudiiarov

Materials 2019, 12(9), 1409; https://doi.org/10.3390/ma12091409 - 30 Apr 2019

Cited by 14 | Viewed by 3044

Abstract

Hydrogen accumulation and distribution in pipeline steel under conditions of enhanced corrosion has been studied. The XRD analysis, optical spectrometry and uniaxial tension tests reveal that the corrosion environment affects the parameters of the inner and outer surface of the steel pipeline as [...] Read more.

Hydrogen accumulation and distribution in pipeline steel under conditions of enhanced corrosion has been studied. The XRD analysis, optical spectrometry and uniaxial tension tests reveal that the corrosion environment affects the parameters of the inner and outer surface of the steel pipeline as well as the steel pipeline bulk. The steel surface becomes saturated with hydrogen released as a reaction product during insignificant methane dissociation. Measurements of the adsorbed hydrogen concentration throughout the steel pipe bulk were carried out. The pendulum impact testing of Charpy specimens was performed at room temperature in compliance with national standards. The mechanical properties of the steel specimens were found to be considerably lower, and analogous to the properties values caused by hydrogen embrittlement. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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17 pages, 6395 KiB

Open AccessArticle

Influence of the Loading Speed on the Ductility Properties of Corroded Reinforcing Bars in Concrete

by Angela Moreno Bazán, María de las Nieves González, Marcos G. Alberti and Jaime C. Gálvez

Materials 2019, 12(6), 965; https://doi.org/10.3390/ma12060965 - 22 Mar 2019

Cited by 2 | Viewed by 2462

Abstract

In this work 144 reinforcing bars of high-ductility steel named B500SD were subjected to an accelerated corrosion treatment and then tested under tension at different loading speeds in order to assess the effect of corrosion on the ductility properties of the rebars. Results [...] Read more.

In this work 144 reinforcing bars of high-ductility steel named B500SD were subjected to an accelerated corrosion treatment and then tested under tension at different loading speeds in order to assess the effect of corrosion on the ductility properties of the rebars. Results showed that the bars with a corrosion level as low as the one reducing the steel mass by 1% gave rise to a significant degradation on the ductility properties when a high loading speed was applied in tensile tests. In that case, the equivalent steel concept is useful to reduce the destabilising effect. Thus, the research significance lies in the assessment of the influence of the loading speed at which the tensile test is performed for the reinforcement bars that largely depends of the ductility criteria used. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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20 pages, 5137 KiB

Open AccessArticle

Corrosion Initiation and Propagation on Carburized Martensitic Stainless Steel Surfaces Studied via Advanced Scanning Probe Microscopy

by Armen Kvryan, Corey M. Efaw, Kari A. Higginbotham, Olivia O. Maryon, Paul H. Davis, Elton Graugnard, Hitesh K. Trivedi and Michael F. Hurley

Materials 2019, 12(6), 940; https://doi.org/10.3390/ma12060940 - 21 Mar 2019

Cited by 11 | Viewed by 3708

Abstract

Historically, high carbon steels have been used in mechanical applications because their high surface hardness contributes to excellent wear performance. However, in aggressive environments, current bearing steels exhibit insufficient corrosion resistance. Martensitic stainless steels are attractive for bearing applications due to their high [...] Read more.

Historically, high carbon steels have been used in mechanical applications because their high surface hardness contributes to excellent wear performance. However, in aggressive environments, current bearing steels exhibit insufficient corrosion resistance. Martensitic stainless steels are attractive for bearing applications due to their high corrosion resistance and ability to be surface hardened via carburizing heat treatments. Here three different carburizing heat treatments were applied to UNS S42670: a high-temperature temper (HTT), a low-temperature temper (LTT), and carbo-nitriding (CN). Magnetic force microscopy showed differences in magnetic domains between the matrix and carbides, while scanning Kelvin probe force microscopy (SKPFM) revealed a 90–200 mV Volta potential difference between the two phases. Corrosion progression was monitored on the nanoscale via SKPFM and in situ atomic force microscopy (AFM), revealing different corrosion modes among heat treatments that predicted bulk corrosion behavior in electrochemical testing. HTT outperforms LTT and CN in wear testing and thus is recommended for non-corrosive aerospace applications, whereas CN is recommended for corrosion-prone applications as it exhibits exceptional corrosion resistance. The results reported here support the use of scanning probe microscopy for predicting bulk corrosion behavior by measuring nanoscale surface differences in properties between carbides and the surrounding matrix. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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24 pages, 8222 KiB

Open AccessFeature PaperArticle

Investigation of the Corrosion Behavior of Atomic Layer Deposited Al₂O₃/TiO₂ Nanolaminate Thin Films on Copper in 0.1 M NaCl

by Michael A. Fusco, Christopher J. Oldham and Gregory N. Parsons

Materials 2019, 12(4), 672; https://doi.org/10.3390/ma12040672 - 24 Feb 2019

Cited by 22 | Viewed by 4827

Abstract

Fifty nanometers of Al₂O₃ and TiO₂ nanolaminate thin films deposited by atomic layer deposition (ALD) were investigated for protection of copper in 0.1 M NaCl using electrochemical techniques. Coated samples showed increases in polarization resistance over uncoated copper, up [...] Read more.

Fifty nanometers of Al₂O₃ and TiO₂ nanolaminate thin films deposited by atomic layer deposition (ALD) were investigated for protection of copper in 0.1 M NaCl using electrochemical techniques. Coated samples showed increases in polarization resistance over uncoated copper, up to 12 MΩ-cm²_, as measured by impedance spectroscopy. Over a 72-h immersion period, impedance of the titania-heavy films was found to be the most stable, as the alumina films experienced degradation after less than 24 h, regardless of the presence of dissolved oxygen. A film comprised of alternating Al₂O₃ and TiO₂ layers of 5 nm each (referenced as ATx5), was determined to be the best corrosion barrier of the films tested based on impedance spectroscopy measurements over 72 h and equivalent circuit modeling. Dissolved oxygen had a minimal effect on ALD film stability, and increasing the deposition temperature from 150 °C to 250 °C, although useful for increasing film quality, was found to be counterproductive for long-term corrosion protection. Implications of ALD film aging and copper-based surface film formation during immersion and testing are also discussed briefly. The results presented here demonstrate the potential for ultra-thin corrosion barrier coatings, especially for high aspect ratios and component interiors, for which ALD is uniquely suited. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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12 pages, 3147 KiB

Open AccessArticle

Inhibitive Properties of Benzyldimethyldodecylammonium Chloride on Microbial Corrosion of 304 Stainless Steel in a Desulfovibrio desulfuricans-Inoculated Medium

by Chung-Wen Hsu, Tzu-En Chen, Kai-Yin Lo and Yueh-Lien Lee

Materials 2019, 12(2), 307; https://doi.org/10.3390/ma12020307 - 18 Jan 2019

Cited by 10 | Viewed by 4230

Abstract

Biocides are frequently used to control sulfate-reducing bacteria (SRB) in biofouling. The increasing restrictions of environmental regulations and growing safety concerns on the use of biocides result in efforts to minimize the amount of biocide use and develop environmentally friendly biocides. In this [...] Read more.

Biocides are frequently used to control sulfate-reducing bacteria (SRB) in biofouling. The increasing restrictions of environmental regulations and growing safety concerns on the use of biocides result in efforts to minimize the amount of biocide use and develop environmentally friendly biocides. In this study, the antimicrobial activity and corrosion inhibition effect of a low-toxic alternative biocide, benzyldimethyldodecylammonium chloride (BDMDAC), on a 304 stainless steel substrate immersed in a Desulfovibrio desulfuricans (D. desulfuricans)-inoculated medium was examined. Potentiodynamic polarization curves were used to analyze corrosion behavior. Biofilm formation and corrosion products on the surfaces of 304 stainless steel coupons were examined using scanning electron microscopy (SEM), energy-dispersive X-ray spectrum, and confocal laser scanning microscopy (CLSM). Results demonstrated that this compound exhibited satisfactory results against microbial corrosion by D. desulfuricans. The corrosion current density and current densities in the anodic region were lower in the presence of BDMDAC in the D. desulfuricans-inoculated medium. SEM and CLSM analyses revealed that the presence of BDMDAC mitigated formation of biofilm by D. desulfuricans. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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19 pages, 4607 KiB

Open AccessArticle

Effect of Electron Donating Functional Groups on Corrosion Inhibition of J55 Steel in a Sweet Corrosive Environment: Experimental, Density Functional Theory, and Molecular Dynamic Simulation

by Ambrish Singh, Kashif R. Ansari, Mumtaz A. Quraishi and Hassane Lgaz

Materials 2019, 12(1), 17; https://doi.org/10.3390/ma12010017 - 21 Dec 2018

Cited by 72 | Viewed by 5690

Abstract

Benzimidazole derivatives were synthesized, characterized, and tested as a corrosion inhibitor for J55 steel in a 3.5 wt % NaCl solution saturated with carbon dioxide. The experimental results revealed that inhibitors are effective for steel protection, with an inhibition efficiency of 94% in [...] Read more.

Benzimidazole derivatives were synthesized, characterized, and tested as a corrosion inhibitor for J55 steel in a 3.5 wt % NaCl solution saturated with carbon dioxide. The experimental results revealed that inhibitors are effective for steel protection, with an inhibition efficiency of 94% in the presence of 400 mg/L of inhibitor. The adsorption of the benzimidazole derivatives on J55 steel was found to obey Langmuir’s adsorption isotherm. The addition of inhibitors decreases the cathodic as well anodic current densities and significantly strengthens impedance parameters. X-ray photoelectron spectroscopy (XPS) was used for steel surface characterization. Density functional theory (DFT) and molecular dynamic simulation (MD) were applied for theoretical studies. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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25 pages, 4959 KiB

Open AccessEditor’s ChoiceReview

Corrosion and Corrosion Protection of Additively Manufactured Aluminium Alloys—A Critical Review

by Reynier I. Revilla, Donovan Verkens, Tim Rubben and Iris De Graeve

Materials 2020, 13(21), 4804; https://doi.org/10.3390/ma13214804 - 28 Oct 2020

Cited by 32 | Viewed by 4263

Abstract

Metal additive manufacturing (MAM), also known as metal 3D printing, is a rapidly growing industry based on the fabrication of complex metal parts with improved functionalities. During MAM, metal parts are produced in a layer by layer fashion using 3D computer-aided design models. [...] Read more.

Metal additive manufacturing (MAM), also known as metal 3D printing, is a rapidly growing industry based on the fabrication of complex metal parts with improved functionalities. During MAM, metal parts are produced in a layer by layer fashion using 3D computer-aided design models. The advantages of using this technology include the reduction of materials waste, high efficiency for small production runs, near net shape manufacturing, ease of change or revision of versions of a product, support of lattice structures, and rapid prototyping. Numerous metals and alloys can nowadays be processed by additive manufacturing techniques. Among them, Al-based alloys are of great interest in the automotive and aeronautic industry due to their relatively high strength and stiffness to weight ratio, good wear and corrosion resistance, and recycling potential. The special conditions associated with the MAM processes are known to produce in these materials a fine microstructure with unique directional growth features far from equilibrium. This distinctive microstructure, together with other special features and microstructural defects originating from the additive manufacturing process, is known to greatly influence the corrosion behaviour of these materials. Several works have already been conducted in this direction. However, several issues concerning the corrosion and corrosion protection of these materials are still not well understood. This work reviews the main studies to date investigating the corrosion aspects of additively manufactured aluminium alloys. It also provides a summary and outlook of relevant directions to be explored in future research. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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25 pages, 1598 KiB

Open AccessReview

Electrochemical Polishing of Austenitic Stainless Steels

by Edyta Łyczkowska-Widłak, Paweł Lochyński and Ginter Nawrat

Materials 2020, 13(11), 2557; https://doi.org/10.3390/ma13112557 - 04 Jun 2020

Cited by 35 | Viewed by 7726

Abstract

Improvement of the corrosion resistance capability, surface roughness, shining of stainless-steel surface elements after electrochemical polishing (EP) is one of the most important process characteristics. In this paper, the mechanism, obtained parameters, and results were studied on electropolishing of stainless-steel samples based on [...] Read more.

Improvement of the corrosion resistance capability, surface roughness, shining of stainless-steel surface elements after electrochemical polishing (EP) is one of the most important process characteristics. In this paper, the mechanism, obtained parameters, and results were studied on electropolishing of stainless-steel samples based on the review of the literature. The effects of the EP process parameters, especially current density, temperature, time, and the baths used were presented and compared among different studies. The samples made of stainless steel presented in the articles were analysed in terms of, among other things, surface roughness, resistance to corrosion, microhardness, and chemical composition. All results showed that the EP process greatly improved the analysed properties of the stainless-steel surface elements. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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22 pages, 5571 KiB

Open AccessReview

AC Corrosion of Carbon Steel under Cathodic Protection Condition: Assessment, Criteria and Mechanism. A Review

by Andrea Brenna, Silvia Beretta and Marco Ormellese

Materials 2020, 13(9), 2158; https://doi.org/10.3390/ma13092158 - 07 May 2020

Cited by 15 | Viewed by 4088

Abstract

Cathodic protection (CP), in combination with an insulating coating, is a preventative system to control corrosion of buried carbon steel pipes. The corrosion protection of coating defects is achieved by means of a cathodic polarization below the protection potential, namely −0.85 V vs. [...] Read more.

Cathodic protection (CP), in combination with an insulating coating, is a preventative system to control corrosion of buried carbon steel pipes. The corrosion protection of coating defects is achieved by means of a cathodic polarization below the protection potential, namely −0.85 V vs. CSE (CSE, copper-copper sulfate reference electrode) for carbon steel in aerated soil. The presence of alternating current (AC) interference, induced by high-voltage power lines (HVPL) or AC-electrified railways, may represent a corrosion threat for coated carbon steel structures, although the potential protection criterion is matched. Nowadays, the protection criteria in the presence of AC, as well as AC corrosion mechanisms in CP condition, are still controversial and discussed. This paper deals with a narrative literature review, which includes selected journal articles, conference proceedings and grey literature, on the assessment, acceptable criteria and corrosion mechanism of carbon steel structures in CP condition with AC interference. The study shows that the assessment of AC corrosion likelihood should be based on the measurement of AC and DC (direct current) related parameters, namely AC voltage, AC and DC densities and potential measurements. Threshold values of the mentioned parameters are discussed. Overprotection (E_IR-free < −1.2 V vs. CSE) is the most dangerous condition in the presence of AC: the combination of strong alkalization close to the coating defect due to the high CP current density and the action of AC interference provokes localized corrosion of carbon steel. Full article

(This article belongs to the Special Issue Corrosion and Protection of Materials)

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