Formation Of Passive Film Research Articles

Enhanced corrosion resistance of Ti[sbnd]Al[sbnd]Mo alloy through solid state transformation driven by rapid solidification

Rapid solidification of undercooled liquid Ti50Al44Mo6 alloy was realized by electromagnetic levitation. Primary (βTi) dendrite grew rapidly from melt with decreasing temperature. As undercooling increased, nucleation rate and growth driving force of primary (βTi) dendrites increased. Growth velocity of primary (βTi) dendrite increased significantly, reaching 13.5 m·s-1 at the maximum undercooling (233 K). After solidification, primary (βTi) dendrite decomposed simultaneously through β→α→α2 transformation and martensite transformation β→γ. Homogeneity of solute distribution in primary (βTi) phase affects the solid-state phase transformation mode. Solid-state phase transition was mainly dominated by diffusion-controlled β→α→α2 transformation at small undercooling. Solid-state phase transition gradually was dominated by displacive martensite transformation at deep undercoolings, and corresponding microstructure was mainly characterized by more refined martensite needles. The refined microstructure and martensite transformation domination contributed to the formation of passivation films with improved corrosion resistance. Moreover, this weakens micro-galvanic effect, significantly reduces size of pits, maintains corrosion scales over pits to effectively alleviate the corrosion process, and consequently enhances corrosion resistance.

Tuning chemical short-range order for stainless behavior at reduced chromium concentrations in multi-principal element alloys

Single-phase multi-principal element alloys hold promise for improved mechanical properties as a result of multiple operative deformation modes. However, the use of many of these alloys in structural applications is limited as a consequence of their poor aqueous corrosion resistance. Here we introduce a new approach for significantly improving the passivation behavior of alloys by tuning the chemical short-range order parameter. We show that the addition of only 0.03 to 0.06 mole fraction of Al to a (FeCoNi)0.9Cr0.1 alloy changed both the magnitude and sign of the Cr-Cr order parameter resulting in passivation behavior similar to 304L stainless steel containing twice the amount of Cr. Our analysis is based on comparing electrochemical measures of the kinetics of passive film formation with chemical short-range order characterizations using time-of-flight neutron scattering, cluster expansion methods, density functional theory and Monte Carlo techniques. Our findings are interpreted within the framework of a recently proposed percolation theory of passivation that examines how selective dissolution of the non-passivating alloy components and short-range order results in excellent passive films at reduced levels of the passivating component.

Microstructure, electrochemical corrosion and corrosion mechanism of electroplated Ni–W alloy coating by DFT calculation

ABSTRACT A Ni–W alloy coating with a thickness of 5 μm was electroplated on N80 steel, and its electrochemical performance in a 3.5% NaCl solution was investigated. The atomic models of passive films and corrosion mechanism were analysed with the density functional theory calculation. The results show that the electroplated Ni–W alloy coating is composed of W atoms in the Ni lattice, and its surface roughness and particle size are 66.1 and 640.4 nm, respectively. The corrosion current density of Ni–W coating is lower than that of the substrate, indicating better corrosion resistance, while the corrosion potential is opposite, which is more passive than the substrate. The total impedance of Ni–W coating is higher than that of the substrate, which is attributed to the formation of NiO passive film during the corrosion process.

Effect of different powers on microstructure evolution and corrosion behavior of 5SiC-Ni60 coatings by directed energy deposition

The microstructural evolution and corrosion behavior of directed energy deposition (DED) additive manufactured 5SiC-Ni60 composite coatings are investigated, elucidating the impact of fluctuations in power on the coating. The experiment reveals the microstructural characteristics, eutectic evolution, phase-microhardness correlation, and corrosion resistance mechanisms, all influenced by power variation as a crucial factor. Utilizing SEM, EDS, XRD, PDP, EIS, and XPS, the mapping relationship between microstructure reinforcement mechanisms, microhardness region features, corrosion behavior formation mechanisms, and power variation is clarified. The optimal laser power is determined to be 3000 W, facilitating the formation of a dense passivation film, efficiently reducing corrosion contact area and enhancing corrosion resistance. The chemical composition of the passivation film is revealed through XPS. Furthermore, utilizing polarization characteristics, impedance analysis, and corrosion morphology as focal points of discussion, the pitting defects on the corroded surface are explained. Consequently, achieving corrosion protection for the composite coating requires intervention with appropriate power parameters, providing valuable insights for enhancing corrosion resistance based on process parameters.

Stability of passive film and pitting susceptibility of 316 L stainless steel in the aggressive oilfield environment containing Cl−-CO2-O2

In this paper, the effects of chloride ions, oxygen, and carbon dioxide on the corrosion resistance of passive films formed on 316 L stainless steel were investigated in the aggressive oilfield environment using electrochemical testing and microscopic characterization techniques. The results showed that Cl− accelerated the anodic dissolution of the metal and compromised the structure and densification of the passive film, thus reducing its corrosion resistance. An increase in the partial pressure of carbon dioxide initially promotes pitting, but subsequently inhibited further corrosion development. The presence of oxygen enhanced the cathodic reaction and passive film formation, effectively preventing the invasion of aggressive chloride ions, thus inhibiting further corrosion. These findings provide a significant scientific basis for material selection and protection of oil extraction equipment in oilfield environments.

Defluoridation by positive single-pulse current electrocoagulation from photovoltaic wastewater: Energy consumption assessment and mechanism analysis

The presence of fluoride ions (F−) in photovoltaic (PV) wastewater significantly affects the integrity of the ecological environment. In contrast to direct current electrocoagulation (DC-EC), positive single-pulse electrocoagulation (PSPC-EC) shows a significant reduction in both the formation of passivation films on electrodes and the consumption of electrical energy. Under the experimental conditions of an Al–Al–Al–Al electrode combination, an electrode spacing of 1.0 cm, a NaCl concentration of 0.05 mol L−1, an initial pH of 5.6, an initial F− concentration of 5 mg L−1, a current density of 5 A m−2, a pulse frequency of 500 Hz, and a 40 % duty cycle, the achieved equilibrium F− removal efficiencies were 84.0 % for DC-EC and 88.0 % for PSPC-EC, respectively, accompanied by power consumption of 0.0198 kWh·mg−1 and 0.0073 kWh·mg−1. The flocs produced in the PSPC-EC process were characterized using scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy and it is revealed that the F− removal mechanisms in the PSPC-EC process include co-precipitation, hydrogen bond complexation, and ion exchange. When the actual PV wastewater was finally subjected to treatment under the optimal PSPC-EC conditions, the F− concentration in the wastewater was reduced from 4.6 mg L−1 to 1.4 mg L−1. This paper provides both a theoretical framework and a technological basis for the application of PSPC-EC in the advanced treatment of PV wastewater.

Microstructural, Electrochemical, and Hot Corrosion Analysis of CoCrFeCuTi High Entropy Alloy Reinforced Titanium Matrix Composites synthesized by Microwave Sintering

CoCrFeCuTi High Entropy Alloy (HEA) is reinforced in Ti6Al6V2Sn alloy through microwave sintering-assisted powder metallurgy and its corrosion behaviour is investigated under different conditions. The ball-milled CoCrFeCuTi HEA powder exhibits 17 μm average particle size of irregular fragments with a single-phase BCC structure and is added as reinforcement in Ti alloy at 3, 6, 9, and 12 wt%. As more reinforcement is added, the α-Ti decreases and β-Ti increases which enhances the interfacial bonding. The pinning effects from reinforcements inhibit grain growth contributing to improved properties including higher relative density with less porosity. The 12 wt% composite showed remarkable microhardness of 734 HV which is increased by 43.8% over Ti alloy. The 12 wt% composite also achieved finer grains (0.345 μm) due to uniform internal heat generation from the process. Corrosion behaviour is assessed through electrochemical corrosion and hot corrosion analysis, with 12 wt% composite demonstrating 59.5% better corrosion resistance compared to Ti alloy. The induced corrosion products, formation of passivation films, and their mechanism are examined by morphological analysis.

A long-lasting passive film formed by dynamic oxygen transport at the interface between coating and substrate

Ce doped α-Fe2O3 nanorods with rich oxygen vacancies (CeFeOx) were prepared using low-temperature oxalate precipitation method and added to epoxy resin as active anti-corrosion filler. In an oxygen rich high-temperature and high-pressure environment (HPHT-O2), the impedance modulus of coatings containing CeFeOx fillers is still close to 1010 Ω·cm2, which is more than 104 times that of pure epoxy coatings. It is attributed to the preferential permeability of CeFeOx fillers to O2, which promotes the formation of a dense passive film on the substrate surface, further hinder corrosion, and ensure that the coating does not peel off from the substrate surface.

Microstructure, wear and corrosion resistance mechanism of as-cast lightweight refractory NbMoZrTiX (X = al, V) high-entropy alloys

Refractory high-entropy alloys (RHEAs) have good overall properties and potential high temperature applications, but they are not competitive in terms of light weight and wear and corrosion resistance, which severely limits the wide range of applications. In this paper, novel NbMoZrTi-X (Al, V) light refractory high entropy alloys (LRHEAs) were fabricated and their physical phase composition, microstructure, hardness, and wear and corrosion resistance were systematically investigated. The results show that NbMoZrTi LRHEA and NbMoZrTiV LRHEA are both single BCC structures, while NbMoZrTiAl LRHEA and NbMoZrTiAlV LRHEA are transformed into BCC, B2, and Zr5Al3 phase structures. The hardness increases as the volume fraction of the Zr5Al3 hard phase increases, with NbMoZrTiAl LRHEA having a maximum Vickers hardness of 811.29 HV. Room temperature dry friction tests showed that NbMoZrTiAl LRHEA had the lowest wear and coefficient of friction of 1.5 mg and 0.6713, respectively. Electrochemical tests performed in 3.5 wt% NaCl solution showed that NbMoZrTiAlV LRHEA has excellent corrosion resistance with the highest Ecorr (−0.142 V) and the lowest Icorr (2.149 × 10−7 A/cm2). Therefore, the addition of V and Al to NbMoZrTi-based LRHEA can effectively improve its wear and corrosion resistance due to the increase in hardness and dense passivation film formation. Our study provides a new strategy for designing LRHEAs with a combination of high hardness and excellent wear and corrosion resistance.

Microstructure and Properties of Ni-WC Composite Plasma Clad

aims: This study aims to improve the surface properties of 45 steel to broaden its applications. background: 45 Steel is an important material for the development of human society and civilisation,and plays an important role in human production and life. Ni-based composite coatings are widely used in metal workpieces to improve the surface properties and expand its applications. objective: In this study, Ni-WC composite coating was prepared on 45 steel substrates by plasma cladding. The microstructure, microhardness, residual stress, and corrosion resistance properties were analyzed to examine various influencing factors. method: In this study, the plasma cladding technique was employed to produce Ni-based cladding with different WC contents on 45 steel surfaces. The microstructure, phase structure, microhardness, residual stress, and corrosion resistance of Ni-based cladding coatings were investigated. result: The results showed that the coatings are made up mostly of Ni3Fe, Cr23C6, Cr7C3, WC, and W2C phases. conclusion: The microhardness of the Ni-based alloy coatings is greatly increased due to the presence of WC hard phase on the Ni matrix. The highest microhardness is more than tripling that of the substrate with the addition of 60% WC. In addition, the largest residual stress at the center of the cladding channel is more than five times higher than the substrate affected zone. The corrosion resistance of 45 steels containing Ni-based coatings increases in acidic, neutral and alkaline environments due to the formation of passivation films. other: none

The synergistic anti‐corrosion performance and mechanism of meso‐tetra(4‐carboxyphenyl)porphine on steel bars in alkaline environments

AbstractCorrosion protection of steel bars in alkaline concrete environments poses a common challenge in marine engineering. One approach to mitigate steel bar corrosion is the addition of corrosion inhibitors to the concrete. In alkaline environments, the passivation of rebars occurs through anodic passivation coupled with the cathodic oxygen reduction reaction (ORR). The catalysis of ORR can expedite anode passivation. To investigate the corrosion inhibition of steel bars in alkaline environments, meso‐tetra(4‐carboxyphenyl)porphine (TCPP), known for its ORR catalytic properties, is selected. TCPP forms adsorption films on the surface of steel bars, facilitating the formation of passivation films. TCPP primarily adsorbs onto active sites on the surface of the passivation film, where lattice iron ions have leached. The adsorbed TCPP accelerates the formation of the passivation film through ORR catalysis, inhibiting the development of passivation film defects and enhancing the integrity and protection of the passivation film. The most significant effect is observed when the concentration of TCPP is 0.5 mmol/L. The physical adsorption of TCPP is primarily determined by the negative charge centers, namely the carboxyl group O and the pyrrole N. However, due to steric hindrance caused by the unrestricted rotation of the carboxyl benzene, the pyrrole N does not play a dominant role in chemical adsorption. Instead, the active site for chemical adsorption is the carboxyl group O. The adsorption process significantly reduces the diffusion coefficient of TCPP molecules, providing a robust and stable adsorption binding. Phthalocyanine molecules without carboxyl benzene groups adopt a planar structure, allowing them to form stable adsorption configurations on the iron surface through flat adsorption. This observation provides guidance for the design of novel metal phthalocyanine molecules. Specifically, the development of metal phthalocyanine molecules with modifying groups that are coplanar with the phthalocyanine ring and possess restricted rotation can achieve flat adsorption, improve coverage rate, and enhance adsorption configuration stability.

Spinodal Zr–Nb alloys with ultrahigh elastic admissible strain and low magnetic susceptibility for orthopedic applications

Metallic biomaterials, such as stainless steels, cobalt–chromium–molybdenum (Co–Cr–Mo) alloys, and titanium (Ti) alloys, have long been used as load-bearing implant materials due to their metallic mechanical strength, corrosion resistance, and biocompatibility. However, their magnetic susceptibility and elastic modulus of more than 100 GPa significantly restrict their therapeutic applicability. In this study, spinodal Zr60Nb40, Zr50Nb50, and Zr40Nb60 (at.%) alloys were selected from the miscibility gap based on the Zr–Nb binary phase diagram and prepared by casting, cold rolling, and aging. Their microstructure, mechanical properties, corrosion resistance, magnetic susceptibility, and biocompatibility were systematically evaluated. Spinodal decomposition to alternating nanoscale Zr-rich β1 and Nb-rich β2 phases occurred in the cold-rolled Zr–Nb alloys during aging treatment at 650 °C. In addition, a minor amount of α phase was precipitated in Zr60Nb40 due to the thermodynamic instability of the Zr-rich β1 phase. Spinodal decomposition significantly improved the mechanical strength of the alloys due to nanosized dual-cubic reinforcement. The Zr–Nb alloys showed an electrochemical corrosion rate of 94–262 nm per year in Hanks’ solution because of formation of dense passive films composed of ZrO2 and Nb2O5 during the polarization process. The magnetic susceptibilities of the Zr–Nb alloys were significantly lower than those of commercial Co–Cr–Mo and Ti alloys. The cell viability of the Zr–Nb alloys was more than 98 % toward MC3T3-E1 cells. Overall, the spinodal Zr–Nb alloys have enormous potential as bone-implant materials due to their outstanding overall mechanical properties, extraordinary corrosion resistance, low magnetic susceptibility, and sufficient bicompatibility. Statement of significanceThis work reports on spinodal Zr–Nb alloys with heterostructure. Spinodal decomposition significantly improved their mechanical strength due to the nanosized dual-cubic reinforcement. The Zr–Nb alloys showed large corrosion resistance in Hanks’ solution because of formation of dense passivation films composed of ZrO2 and Nb2O5 during the polarization process. The magnetic susceptibilities of the Zr–Nb alloys were significantly lower than those of commercial Co–Cr–Mo and Ti alloys. The cell viability of the Zr–Nb alloys was more than 98 % toward MC3T3-E1 cells. The results demonstrate that spinodal Zr–Nb alloys have enormous potential as bone-implant materials due to their outstanding overall mechanical properties, high corrosion resistance, low magnetic susceptibility, and sufficient biocompatibility.

Cations effect on the passive film for carbon steels in concrete simulated pore solutions

The composition of the passive film on the carbon steel surface is a key step for understanding the protective properties of the carbon steel in concrete environment. Since the different cation ions lead the different protective properties, the impacts of different cation ions (Ca2+ and Na+) exposed in simulated pore solutions on the passive film formation at the passivation stage are investigated by electrochemical measurements and surface analysis methods. To reveal the main reasons for the protective properties of the passive film and clarify the evolution for the formation of the passive film under different cation ions. Electrochemical measurements show that most part of the passive film has already formed in the initial 72 h in an NH solution, whereas 168h is needed to form most of the passive in a CH solution. In addition, 216 h is enough to form a completed passive film during the natural passivation period. Surface analysis methods elucidate the passive film formed in a CH solution has more protective properties than that in an NH solution because more iron oxides are produced. Furthermore, the presence of Ca2+ ions in the pore solution significantly improves the protective properties of the passive film.

Corrosion behavior of SiC/Ti6Al4V titanium matrix composites fabricated by SLM

In this paper, Ti6Al4V alloy and Ti6Al4V-SiCw composites were formed by selective laser melting (SLM) and electrochemical corrosion experiments were carried out. The effects of different SiCw contents and solid solution aging heat treatment on the corrosion properties of the composites were systematically studied, and the corrosion mechanism of Ti6Al4V-SiCw composites was revealed. The results show that Ti6Al4V-1SiCw composites have better corrosion resistance than Ti6Al4V alloy. After solution and aging heat treatment at 1050 °C, Ti6Al4V-1SiCw composites have better corrosion resistance. The main reasons for the improvement of the corrosion performance of the composites are as follows: (i) The high-density grain boundaries formed by grain refinement of the composites have higher energy and are more likely to react to form a stable passivation film. (ii) The microstructure of Ti6Al4V-SiCw composites is equiaxed α phase, which is easier to form stable passivation film than metastable α′-Ti phase. (iii) The presence of ceramic particles makes more microcells formed in the titanium matrix, which promotes the formation of soluble [TiCl6]2- complexes. The formation of passivation film on the surface of Ti6Al4V-SiCw composites was accelerated.

Smart Doped Polyaniline Coating for Wireless Anodic Protection of AISI 304 Stainless Steel in a Corrosive Medium Containing Sulfate and Chloride Ions: Electrochemical and DFT Evaluations.

Polyaniline (PANI) coatings have the capability of in situ anodic protection of stainless steels (SSs). However, these coatings have a high degradation rate in sulfuric acid. Also, the protection of SSs in a medium contaminated with chloride ions is an unsolved challenge. Therefore, the present work aims to modify the electrodeposited PANI coating with different dopants to find the optimal coating for the anodic protection of 304 SS in chloride-contaminated sulfuric acid. Thus, CH3COO-, HSO4-, NO3-, H2PO4-, and NaSO4- were doped electrochemically in PANI to determine the most effective corrosion depressor. Density functional theory (DF)T calculations determined that the lowest Gibbs free energy (more spontaneous doping) is for HSO4- doping by 24 kcal/mol. The band gap energy is <0.5 eV for the PANI/H2SO4 coating, indicating the very high conductivity of this coating. Monte Carlo simulation revealed that the highest deformation energy is related to PANI/H2SO4 at 1877 kcal/mol (stronger adsorption). Mott-Schottky and energy-dispersive spectroscopy (EDS) results showed that PANI doped with sulfuric acid creates a p-type semiconductor (Ni-rich), while the rest of the dopants lead to the formation of an n-type semiconductor passive film (Fe/Cr-rich). Despite the relatively low corrosion resistance of PANI/H2SO4 in the early days, its resistance improved over time by more than 1 order of magnitude. Therefore, this seems to be a more favorable option for long-term anodic protection. Thus, in this work, the corrosion behavior of the passive film formed at the interface of PANI and SS was comprehensively evaluated.

Effects of magnetic fields on the formation of passive films on the surface of 5083 aluminum alloy

This research explores the effect of the magnetic fields on the passive film of 5083 aluminum alloy. After the application of a 0.3 T magnetic field, 5083 aluminum alloy exhibits an improvement in passivation performance. These improvements manifest as a reduction in passivation current density and an increase in impedance, passive film thickness, and carrier concentration. Additionally, there is an augmentation in the content of the Al2O3 phase within the passive film. The magnetic field facilitates the movement of metal ions during the corrosion process of 5083 aluminum alloy through microscale magnetohydrodynamics, facilitating passive film growth and improving corrosion resistance.

Electrochemical behavior and microstructural characterization of nano-SiC particles reinforced aluminum matrix composites prepared via friction stir processing

The present work aims to elucidate the mechanism of microstructural evolution in different regions of nano-SiC particles reinforced aluminum matrix composites prepared by friction stir processing (FSP) on its electrochemical behavior. Electron backscatter diffraction technique (EBSD) and transmission electron microscopy (TEM) were employed to characterize the microstructure evolution of stir zone (SZ), advancing side thermomechanically affected zone (AS-TMAZ), retreating side thermomechanically affected zone (RS-TMAZ) and base metal (BM). The electrochemical behaviors of the above zones were investigated using electrochemical tests. A homogeneous and fine microstructure is formed in SZ, not only the nano-SiC is homogeneously distributed within the grains with an average grain size of 3.5 μm, but also the recrystallized grains account for the highest percentage of 85 %. The potentiodynamic polarization curve indicates that the corrosion current densities of the BM, RS-TMAZ, AS-TMAZ and SZ are 0.89, 0.39, 0.85 and 0.36 μA/cm2, respectively, while the polarization impedances are 33.40, 51.42, 48.72 and 73.79 kΩ cm2, respectively. Combining the Nyquist and Bode plots analysis, the optimal electrochemical corrosion resistance is in SZ. The fine and homogeneous recrystallized grains in SZ significantly improve its electrochemical corrosion resistance. This is mainly ascribed to the increase in crystal defects as a result of the increase in grain boundaries, elevating the electron scattering. Simultaneously, the increase in high-energy state grain boundaries is beneficial to the rapid formation of a thicker passivation film.

Carbon dioxide and weak magnetic field enhance iron-carbon micro-electrolysis combined autotrophic denitrification

Combining iron-carbon micro-electrolysis and autotrophic denitrification is promising for nitrate removal from wastewater. In this study, four continuous reactors were constructed using CO2 and weak magnetic field (WMF) to address challenges like iron passivation and pH stability. In the reactors with CO2 + WMF (10 and 35 mT), the increase in total nitrogen removal efficiency was significantly higher (96.2 ± 1.6 % and 94.1 ± 2.7 %, respectively) than that of the control (51.6 ± 2.7 %), and Fe3O4 converted to low-density FeO(OH) and FeCO3, preventing passivation film formation. The WMF application decreased the N2O emissions flux by 8.7 % and 20.5 %, respectively. With CO2 + WMF, the relative enzyme activity and abundance of denitrifying bacteria, especially unclassified_Rhodocyclaceae and Denitratisoma, increased. Thus, this study demonstrates that CO2 and WMF optimize the nitrate removal process, significantly enhancing removal efficiency, reducing greenhouse gas emissions, and improving process stability.

Comparative Study on Passive Film Formation Mechanism of Cast and PBF-LB/M-TC4 in Simulated Physiological Solution.

Personalized laser powder bed fusion (PBF-LB/M) Ti-6Al-4V (TC4) has a broader application prospect than that of traditional casting. In this paper, the composition and corrosion resistance of the passive film formation mechanism of TC4 prepared by optimization of PBF-LB/M techniques and traditional casting were systematically studied in 0.9 wt.% NaCl at 37 °C by electrochemical technique and surface analysis. The rates of the passive film formation process, corrosion resistance and composition of TC4 show different characteristics for the different preparation processes. Although the rate of passive film formation of cast-TC4 was higher at the initial immersion, the open circuit potential was more positive, and the film thickness was larger after stabilization, those facts show no positive correlation with corrosion resistance. On the contrary, with no obvious defects on the optimized PBF-LB/M-TC4, the passive film resistance is 2.5 times more, the defect concentration is reduced by 30%, and the TiO2 content is higher than that of the cast-TC4, making the martensitic-based PBF-LB/M-TC4 exhibit excellent corrosion resistance. This also provides good technical support for the further clinical application of PBF-LB/M-TC4.

Study on the corrosion performance of supersonic atmospheric plasma sprayed Cr3C2-NiCr coatings

PurposeDue to the harsh underground environment in coal mining, the surface of hydraulic support columns corrodes severely, resulting in significant economic losses. Therefore, a highly corrosion-resistant coatings is needed to extend the service life of the columns.Design/methodology/approachThis study aims to compare the corrosion resistance of ST-Cr3C2-NiCr (sealed treatment Cr3C2-NiCr) coatings with industrially applied chromium plating. The corrosion failure mechanism of the coatings was investigated.FindingsThe results demonstrated that the ST-Cr3C2-NiCr coatings exhibited excellent corrosion resistance. After sealing treatment, the corrosion potential of Cr3C2-NiCr coatings was −0.215 V, and the corrosion current density of Cr3C2-NiCr coatings was lower than that of the plated parts.Practical implicationsST-Cr3C2-NiCr coatings prepared by supersonic atmospheric plasma spraying could provide excellent corrosion resistance in the coal industry.Originality/valueThe low porosity and the presence of the NiCr phase were crucial factors contributing to the preferable corrosion resistance exhibited by the ST-Cr3C2-NiCr coatings. The corrosive process of the coatings involved layer-by-layer delamination of surface oxide film, sub-surface pitting, formation and degradation of sub-surface passive film, as well as severe block-like delamination.