Corrosion Resistance Of Alloy Research Articles

Corrosion and Interfacial Contact Resistance of NiTi Alloy as a Promising Bipolar Plate for PEMFC

Titanium (Ti) is generally considered as an ideal bipolar plate (BPP) material because of its excellent corrosion resistance, good machinability and lightweight nature. However, the easy-passivation property, which leads to increased interfacial contact resistance (ICR) and subsequently decreased cell performance, limits its large-scale commercial application in proton exchange membrane fuel cells (PEMFCs). In this paper, we proposed a NiTi alloy prepared by suction casting as a promising bipolar plate for PEMFCs. This NiTi alloy exhibits significantly decreased ICR values (16.8 mΩ cm2 at 1.4 MPa) compared with pure Ti (88.6 mΩ cm2 at 1.4 MPa), along with enhanced corrosion resistance compared with pure nickel (Ni). The superior corrosion resistance of NiTi alloy is accredited to the nobler open circuit potential and corrosion potential, coupled with low corrosion current densities and passive current densities. The improved ICR can be interpreted by the existence of high-proportioned metallic Ni in the passive film, which contributes to the reduced capacitance characteristic of the passive film (compared with Ti) and enhances charge conduction. This work provides a feasible option to ameliorate BPP material that may have desirable corrosion resistance and ICR.

Corrosion Resistance of Coatings Based on Chromium and Aluminum of Titanium Alloy Ti-6Al-4V

Improvement of wear, corrosion, and heat-resistant properties of coatings to expand the operational capabilities of metals and alloys is an urgent problem for modern enterprises. Diffusion titanium, chromium, and aluminum-based coatings are widely used to solve this challenge. The article aims to obtain the corrosion-electrochemical properties and increase the microhardness of the obtained coatings compared with the initial Ti-6Al-4V alloy. For this purpose, corrosion resistance, massometric tests, and microstructural analysis were applied, considering various aggressive environments (acids, sodium carbonate, and hydrogen peroxide) at different concentrations, treatment temperatures, and saturation times. As a result, corrosion rates, polarization curves, and X-ray microstructures of the uncoated and coated Ti-6Al-4V titanium alloy samples were obtained. Histograms of corrosion inhibition ratio for the chromium–aluminum coatings in various environments were discussed. Overall, the microhardness of the obtained coatings was increased 2.3 times compared with the initial Ti-6Al-4V alloy. The corrosion-resistant chromaluminizing alloy in aqueous solutions of organic acids and hydrogen peroxide was recommended for practical application in conditions of exposure to titanium products.

Development of high corrosion resistant (Ni-Fe) alloy coatings from a low concentration bath through multilayer approach

Development of high corrosion resistant (Ni-Fe) alloy coatings from a low concentration bath through multilayer approach

Corrosion Resistance of FeCrMnxAlCu High-Entropy Alloys in 0.5 M H2SO4 Solution

In this study, FeCrMnxAlCu high-entropy alloys with varying Mn contents (x = 2.0, 1.5, 1.0, 0.5, and 0) were prepared using a vacuum arc melting furnace. The phase structure and microstructure of the alloys before and after corrosion were characterized via X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The corrosion resistance of the alloys in a 0.5M H2SO4 solution was comprehensively evaluated through potentiodynamic polarization, electrochemical impedance spectroscopy, immersion tests, white light interferometry, and X-ray photoelectron spectroscopy. Microstructural characterization results revealed that the FeCrMnxAlCu high-entropy alloys exhibited mixed FCC and BCC phase structures and featured typical dendritic and interdendritic regions. Corrosion tests indicated that as the Mn content decreased, the corrosion resistance of the high-entropy alloys improved, and the corrosion type transitioned from dendritic to interdendritic. Among these alloys, the FeCrAlCu high-entropy alloy exhibited the highest corrosion resistance, with the highest positive corrosion potential (Ecorr = −0.11V), the lowest corrosion current density (Icorr = 1.02 × 10−5 A∙cm2), minimal corrosion depth, and the lowest corrosion rate (0.1592mm/y). After corrosion, a composite oxide protective film was formed on the alloy surface, effectively hindering further penetration of the H2SO4 solution and exhibiting excellent corrosion resistance.

Utilization of Alumina Scale Formation by Ni-Base Alloys for High-Temperature Oxidation and Corrosion Resistance in Harsh Environments

Utilization of Alumina Scale Formation by Ni-Base Alloys for High-Temperature Oxidation and Corrosion Resistance in Harsh Environments

Microstructure, corrosion resistance and high temperature oxidation properties of AlCrFeNiCu high-entropy alloy coating by high-speed laser cladding

AlCrFeNiCu high-entropy alloy (HEA) coating was prepared on Zirconium (Zr) rod by high-speed laser cladding (HSLC) technique. The effect of different laser power and scanning speed on the forming quality of the coating was studied. When the specific energy density was in the range of 3.0–3.2 J/mm2, the AlCrFeNiCu HEA coating with good adhesion to the substrate, low dilution rate (small heat affected zone) and no cracks were obtained. The phase structure, microstructure, microhardness, corrosion resistance and high temperature oxidation resistance of the coating were tested and analyzed. The results show that the AlCrFeNiCu HEA coating is composed of 76.9 % BCC phase and 23.1 % FCC phase, in which the BCC phase is mainly composed of disordered BCC phase rich in Cr and Fe elements and ordered B2 phase rich in Al and Ni elements, and the FCC phase is rich in Cu elements. Due to the rapid cooling of HSLC, the coating structure gradually changes from columnar crystal to equiaxial crystal from bottom to top. The hardness of the coating is as high as 805 HV, which may be caused by the solution strengthening effect, lattice distortion effect and slow diffusion effect of HEA. In 3.5 % NaCl solution and 0.1 mol/L KOH solution, the self-corrosion current density of the coating is 4.209 × 10−8 A/cm2 and 4.331 × 10−8 A/cm2, respectively. The passivation film on the surface of the coating is composed of a variety of oxides, and the oxygen vacancy density of the passivation film in the two solutions is 2.552 × 1020 cm−3 and 5.794 × 1020 cm−3, with fewer pitting pits on the surface. The structural integrity of the coating can be maintained after 60 min oxidation at 1200 °C. The oxidation process follows the growth kinetics curve, and the surface oxides mainly comprise FeAl2O4, Al2O3 and Cr2O3. AlCrFeNiCu HEA coating improves the corrosion resistance and high temperature oxidation resistance of the Zr-4 alloy.

Numerical simulation and properties analysis of Ta10W alloy joints prepared by electron beam welding

Vacuum electron beam welding has the characteristics of concentrated energy, controllable heat input, almost no pollution, and a small heat-affected zone. In this study, the Ta10W alloy was successfully connected by electron beam welding (EBW), and numerical simulations were employed to examine the distribution of temperature and stress fields throughout the welding process. Additionally, the influence of EBW on the microstructure and corrosion resistance of the welded joints was scrutinized. Findings indicate that the welding heat process led to a reduction in grain boundary energy, thereby facilitating thermal activation processes that contributed to grain growth. Grain boundary migration and possible dynamic crystallization led to the appearance of the coarse columnar crystal structure in the welded joint. A three-dimensional, nonlinear, transient, thermo-mechanically coupled finite element model was developed for the electron beam welding of Ta10W alloy. The shape characteristics and size of the weld and transient thermal cycles calculated by numerical simulations were in reasonable agreement with experimental results. Electron beam welding reduced the corrosion resistance of the Ta10W alloy, and the corrosion product was mainly composed of Ta, O and Na.

Exploring high corrosion-resistant refractory high-entropy alloy via a combined experimental and simulation study

Refractory high-entropy alloys (HEAs) have attracted considerable attention due to their stable phase structure and excellent high-temperature properties. In this work, we performed first-principles calculations, coupled with experiments, to explore HEAs with high corrosion resistance. The results revealed that TiNbTa-based HEAs exhibited a lower tendency for corrosion. However, the appearance of local chemical fluctuations (LCFs) increased the corrosion tendency of TiNbTa-based HEAs. Comprehensive SHapley Additive exPlanations analyses uncovered that in a sample with configurational LCFs, the atomic order near the surface was altered. Therefore, corrosion behavior was affected. Based on experiments, the annealed samples exhibited typical chemical segregation and declined corrosion resistance.

Oxidation behavior and corrosion resistance of CoCrFeNi high entropy alloy compared with FeCoNi medium entropy alloy

The entropy-based alloy with excellent oxidation and corrosion resistance is of great significance for practical applications in high-temperature environments. Thus, the difference in anti-oxidation property and corrosion behavior of FeCoNi MEA and CoCrFeNi HEA in a simulated marine environment was studied via a series of measurements. The results reveal that the HEA possesses superior oxidation and corrosion resistance in comparison with the MEA, which can be demonstrated by comparing the oxidation rate and thickness of oxide layer, corrosion current density (icorr) as well as corrosion morphology after polarization. The microstructure and composition of the oxide layer are the primary reasons resulting in the difference of oxidation and corrosion behaviors of the two alloys. The oxide layer with a compact, even and intact structure is produced on the HEA surface, which hinders the diffusion of detrimental ions and oxygen, whereas the loose, porous and cracked oxide layer consisting of inner Fe3O4 and outer CoO exhibits poor protection against corrosion and oxidation of the MEA. For the HEA, the preferential combination of Cr and O elements forms the protective oxide of Cr2O3, effectively enhancing corrosion resistance and inhibiting oxidation. However, the low protective CoO and relatively active Fe3O4 grow on the MEA surface, which cannot provide a good barrier to restrain oxidation and corrosion.

Selective atomic sieving across metal/oxide interface for super-oxidation resistance

Surface passivation, a desirable natural consequence during initial oxidation of alloys, is the foundation for functioning of corrosion and oxidation resistant alloys ranging from industrial stainless steel to kitchen utensils. This initial oxidation has been long perceived to vary with crystal facet, however, the underlying mechanism remains elusive. Here, using in situ environmental transmission electron microscopy, we gain atomic details on crystal facet dependent initial oxidation behavior in a model Ni-5Cr alloy. We find the (001) surface shows higher initial oxidation resistance as compared to the (111) surface. We reveal the crystal facet dependent oxidation is related to an interfacial atomic sieving effect, wherein the oxide/metal interface selectively promotes diffusion of certain atomic species. Density functional theory calculations rationalize the oxygen diffusion across Ni(111)/NiO(111) interface, as contrasted with Ni(001)/NiO(111), is enhanced. We unveil that crystal facet with initial fast oxidation rate could conversely switch to a slow steady state oxidation.

A novel strategy to enhance the mechanical properties and corrosion resistance of ultra-high strength Al-Zn-Mg-Cu alloy: Pre-recovery Multi-Stage Solution Treatment (P-MST)

This study proposed a novel solution treatment method: Pre-recovery Multi-Stage Solution Treatment (P-MST), which involved a pre-recovery treatment before the conventional MST. Hardness testing results indicated that the recrystallization initiation temperature of the alloy is around 240 °C. Through in-depth analysis of the microstructure, mechanical properties, and corrosion resistance of samples subjected to conventional MST (450 °C/2h + 460 °C/2h + 470 °C/2h, water quenched), P-MST-350 °C (350 °C/12h + MST), and P-MST-250 °C (250 °C/12h + 350 °C/12h + MST), it was found that under the treatment of 350 °C/12 h and 250 °C/12 h + 350 °C/12 h, some MgZn2 phases were dissolved, resulting in a decrease in the area fraction of residual secondary phases and refinement in their size, leading to a higher degree of solid solution for Zn and Mg in the alloy. Simultaneously, pre-recovery treatment not only suppressed recrystallization phenomena and decreased intragranular dislocation density, but also caused the intragranular aging precipitates to transition from η' + η to GP zones + η′, with smaller precipitate sizes. Consequently, the alloy's tensile strength, elongation, and corrosion resistance showed significant improvement. Compared to the MST sample, the P-MST-250 °C sample exhibited enhancements in yield strength, ultimate tensile strength, and elongation from 725 MPa, 741 MPa, and 4.1 % to 778 MPa, 802 MPa, and 6.5 %, respectively. Quantitative calculations demonstrated that solid solution strengthening, low-angle grain boundary strengthening, and aging precipitation strengthening contributed approximately 9.6 MPa, 26.3 MPa, and 43.3 MPa, respectively, while the dislocation strengthening decreased 27.3 MPa to the yield strength of the alloy.

Corrosion behavior of SMSS 13Cr and SS 316L under chloride solution and H2S/CO2 environments

Abstract Corrosion resistant alloys (CRAs) include a range of different stainless steels and nickel alloys that are used in corrosion-aggressive environments encountered in oil and gas operations. Supermartensitic stainless steel (SMSS 13Cr) has been used in the manufacture of steel tubes for use in oil drilling due a more financially viable option to replace the austenitic stainless steel (SS 316L) in the oil and gas market. This present work estimate the effect of the hydrogen sulphide (H2S) on SMSS 13Cr and SS 316L, in saline solution, simulating the operating conditions in the oil and gas industry. Corrosion behavior was monitored using Potentiodynamic-Potentiostatic-Potentiodynamic (PD-PS-PD) technique in order to obtain pitting potential (Ep) or crevice potential (Ecrev)) and repassivation potential (Erp) while the long-term Open Circuit Potential (OCP) technique was applied to estimate the stable corrosion potential (Ecorr*). A Scanning Electron Microscope (SEM) equipped with Energy Dispersive X-ray Spectroscopy (EDS) and Optical Microscopy were used for surface characterization. With all analysis carried out was possible to propose a trend regarding the pitting probability. The pitting increases with increasing H2S concentration on SSSM 13Cr, consequently, large, and deeper pits were observed, making possible to develop into cracks if there are mechanical stresses. On the contrary, the pitting probability for the SS 316L is low (compared with SMSS 13Cr) for all environments reproduced here in this research.

Effects of Zr additions and process annealing on mechanical and corrosion properties of AA5383 Al–Mg alloys

Abstract The study investigates how Zr additions and process annealing affect mechanical and corrosion properties of AA5083 Al–Mg alloys by microstructural examination, tensile strength, hardness testing and ASTM G67 nitric acid mass loss test. In the present work, process annealing temperatures were set to 220 °C and 250 °C. The results show that the hardness and tensile properties of Zr-containing cold rolled alloy were superior to that of Zr-free cold rolled alloy before and after process annealing treatment and sensitization heat treatment. Unfortunately, adding Zr to AA5383 alloy significantly degraded the corrosion resistance of the Zr-containing cold rolled alloy annealed at 220 °C. For improving corrosion resistance of Zr-containing alloy, annealing temperature could be increased to 250 °C to avoid a marked drop in the corrosion resistance.

Influence of Single- and Double-Aging Treatments on the Mechanical and Corrosion Resistance of Alloy 625

Nickel–chromium–molybdenum Alloy 625 exhibits an excellent combination of mechanical properties and corrosion resistance. However, the high-temperature plastic deformation process and the heat treatment represent critical aspects for the loss in mechanical strength by grain coarsening. This detrimental behavior is worsened by the absence of phase transformation temperatures. However, the chemical composition permits slow precipitation-hardening response upon single aging. Therefore, when the soft- or solution-annealed condition is associated with insufficient mechanical properties, this potentiality can be exploited to improve the mechanical strength. Since the 𝛾″ precipitation can be accelerated by double-aging treatment, different time–temperature combinations of double aging at 732 °C and 621 °C are investigated. The simultaneous precipitation of intergranular carbides can dramatically affect the corrosion resistance. Such an undesired phenomenon occurs very quickly at 732 °C, but it is obtained only after very long exposure times at 621 °C. For this reason, a performance chart is developed to compare all the tested conditions. In particular, single aging at 621 °C for 72 h and 130 h are associated with an acceptable combination of mechanical and corrosion properties. Double aging permits a conspicuous acceleration of the aging response. For instance, with double aging at 732 °C 3 h and 621 °C 72 h, it is possible to obtain the same mechanical properties of single aging at 621 °C for 260 h. Such acceleration is accompanied by a more critical corrosion behavior, especially because of the primary step. However, even after its optimization, none of the tested conditions were acceptable.

Multi-Species Biofilm Interactions and Their Impact on the Biocorrosion of Copper-Coated CoCr Alloys in Dental Application

Biocorrosion of materials used in dental restorations is a complex process involving various bacterial species that coexist as biofilms. Since copper possesses excellent antibacterial properties, it could help minimize this problem. The aim of this study is to assess the antibiofilm characteristics and corrosion resistance of CoCr and copper-coated CoCr alloys in a multispecies biofilm model. CoCr alloys and CoCr coated with copper (CoCr/Cu) using Physical Vapor Deposition (PVD) were investigated. The samples were incubated in media with and without a multispecies biofilm for 24 h and for 15 days. Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy (EIS) were used to assess the corrosion behavior of the samples. Scanning Electron Microscopy (SEM) was utilized to observe the growth of multispecies biofilms and the type of corrosion. The Mann–Whitney U test was employed to examine corrosion results, with significant differences defined as p < 0.05. CoCr/Cu alloys demonstrated superior corrosion resistance at 24 h and 15 days in the presence of biofilm compared to those without coating. No differences were observed in multispecies biofilm formation at 24 h. The study demonstrates that copper-coated CoCr alloys (CoCr/Cu) exhibit a more positive corrosion potential (Ecorr) compared to uncoated CoCr alloys, both in the presence and absence of multispecies biofilm (BP) at 24 h and 15 days. After 15 days, the potential of CoCr/Cu with BP was −0.144 V, compared to −0.252 V for uncoated CoCr. These significant differences in Ecorr values underscore the protective effect of copper against corrosion in multispecies biofilm environments.

Focused review on factors affecting martensitic stainless steels and super martensitic stainless steel passive film in the oil and gas field

AbstractMartensitic and super martensitic stainless steels are widely used in the oil and gas industry for general corrosion mitigation in the presence of sweet corrosion (CO2) and sour corrosion (H2S), providing a cost-effective alternative to more expensive exotic corrosion-resistant alloys. Martensitic stainless steel is an approved material for construction when selecting tubular CO2 injection wells. This work aims to review the published literature on the subject of the operation limits of martensitic stainless steel and super martensitic stainless steel in high temperatures and high pressure under corrosive environments. Stress corrosion cracking (SCC) and sulfide stress corrosion cracking (SSCC) mechanisms on martensitic and super martensitic stainless steel surfaces are thoroughly analyzed. In this review paper, we have analyzed the factors that play a crucial role in passive film growth and passivity breakdown. The present work is to review the state of the art of mechanism responsible for SCC and SSCC susceptibility in different modified martensitic stainless steel materials, which are applied to the industry and lab scale. We have reviewed the effect of different concentrations of molybdenum content on SCC and SSCC susceptibility of conventional martensitic stainless steel, modified martensitic stainless steel, and super martensitic stainless steel. The effect of tempering temperature on the SCC and SSCC performance of the martensitic and super martensitic stainless steel was also studied. We also studied the effect of different concentrations of chromium on the improved corrosion-resistant properties and stability of passivation film.

Focused review on factors affecting martensitic stainless steels and super martensitic stainless steel passive film in the oil and gas field

AbstractMartensitic and super martensitic stainless steels are widely used in the oil and gas industry for general corrosion mitigation in the presence of sweet corrosion (CO2) and sour corrosion (H2S), providing a cost-effective alternative to more expensive exotic corrosion-resistant alloys. Martensitic stainless steel is an approved material for construction when selecting tubular CO2 injection wells. This work aims to review the published literature on the subject of the operation limits of martensitic stainless steel and super martensitic stainless steel in high temperatures and high pressure under corrosive environments. Stress corrosion cracking (SCC) and sulfide stress corrosion cracking (SSCC) mechanisms on martensitic and super martensitic stainless steel surfaces are thoroughly analyzed. In this review paper, we have analyzed the factors that play a crucial role in passive film growth and passivity breakdown. The present work is to review the state of the art of mechanism responsible for SCC and SSCC susceptibility in different modified martensitic stainless steel materials, which are applied to the industry and lab scale. We have reviewed the effect of different concentrations of molybdenum content on SCC and SSCC susceptibility of conventional martensitic stainless steel, modified martensitic stainless steel, and super martensitic stainless steel. The effect of tempering temperature on the SCC and SSCC performance of the martensitic and super martensitic stainless steel was also studied. We also studied the effect of different concentrations of chromium on the improved corrosion-resistant properties and stability of passivation film.

Design of corrosion-resistant alloys for preventing oxidation-induced nanoscale Cr-depletion by inclusion engineering

Due to the preferential oxidation of Cr in various corrosion-resistant alloys, Cr-depletion extensively forms around the oxides and impairs passivation ability. This harmful effect has been widely recognized, but available solutions are limited. Here, to prevent such oxidation-induced Cr-depletion in corrosion-resistant alloys, we proposed a general strategy based on inclusion engineering using oxygen-preferred elements in alloy design. The inclusion-Cr depletion-passivation relationship was systematically studied in 3.5 wt% NaCl using commercially cast original, Si-modified, Al-modified, and Ti-modified CoCrFeMnNi alloys, in which the prominent inclusions were identified as MnCr2O4, MnO-SiO2, AlN, and TiN, respectively. Unlike the original alloy, all modified alloys prevented Cr-depletion with improved corrosion resistance; however, the Si-modified alloy exhibited the most remarkable improvement due to few nitride by-products. Thermodynamic analysis on the free energy changes of potential reactions revealed that all the additives were preferential to be oxidized over Cr, whereas Al and Ti nitridation reactions have the most negative free energies compared to all oxidation reactions, which validated experimental results. From experiments and thermodynamics, an effective method was proposed, and its application was discussed with three newly-designed alloys prepared using arc melting. We believe the proposed strategy can be widely used in designing alloys to prevent oxidation-induced Cr-depletion.

A Microporous Channel Copper Immersion Layer Promotes the Rapid Ni-P Electroless Plating Process on Aluminum Alloys at Medium and Low Temperatures

Abstract Electroless plating is a commonly used method to enhance the corrosion resistance, wear resistance, and decorative performance of aluminum alloys. However, in electroless plating processes, it is customary to maintain the solution temperature at levels exceeding 85°C, a critical condition that ensures a sufficiently rapid deposition rate and thereby fosters the formation of high-performance coatings. Conventional immersion pretreatments with zinc and palladium result in lower deposition rates at low temperatures. This study shows that a copper immersion layer with microporous channels can facilitate the electroless plating process for aluminum alloys at lower temperatures. Through a redox reaction in a Cu2+-containing solution at 70°C, a copper immersion layer with a microporous structure could be created on an aluminum alloy. The microporous channels between the copper immersion layer and the aluminum alloy create electrochemical corrosion cells in the plating solution, accelerating the electroless plating process. The Ni-P coating obtained after pretreatment by copper immersion has a higher hardness (578 HV) and a lower corrosion current density (0.55 μA/cm2). This work provides a practical method to rapidly fabricate high-performance Ni-P coatings at intermediate temperatures (70-75°C).

Local valence analysis of 316L austenitic stainless steel produced by laser powder bed fusion

Ultra-rapid cooling of laser powder bed fusion (LPBF) generates a cellular solidification microstructure with submicron-sized periodicity accompanied by non-negligible segregation. In 316L austenitic stainless steel, an important corrosion-resistant alloy, the effect of segregation, particularly variations in Cr concentration, on the corrosion resistance of the LPBF product is unknown. Local valence analysis of the LPBF-produced 316L by electron energy-loss spectroscopy revealed no obvious changes in the energy-loss near-edge structures of Cr and Fe measured within the solidification cellular microstructure, at the cell boundary, or at the melt-pool boundary. This result indicates that solidification segregation in the LPBF-produced 316L is unlikely to affect the corrosion resistance of the material.