Corrosion Resistance Of Layers Research Articles

Effect of Pinless Friction Stir Processing on Microstructure and Properties of Surface Modification Layer of 2024 Aluminum Alloy

Abstract Friction stir processing (FSP) is an advanced material surface modification technology that is both green and energy-efficient. This technology plays a crucial role in regulating the surface microstructure of alloys and improving their material surface properties. It achieves this through the synergistic effect of non-equilibrium thermodynamics and surface mechanical deformation. In this work, the surface modification of an aluminum alloy was performed using pin-less FSP. And the modified surface was then analyzed using stress-strain curves, optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical tests to investigate the impact of spindle velocity on the modified layer's properties. Results of the study show after undergoing pin-free FSP modification treatment, the surface of the alloy appears bright and flat. The modified layer displays refined grains and numerous dispersed second-phase particles. Furthermore, the grains in the modified layer exhibit a gradient distribution from the surface to the matrix. Regarding the properties, Compared to the base material (BM), the yield strength (σ0.2) and tensile strength (σb) of the alloy-modified layer were increased by 34.8% and 29.4%, respectively. The maximum elongation (δ) of the modified coating reached 22.3%. The modified layer exhibits a tough-brittle mixed fracture pattern. Additionally, the modified layer's corrosion resistance significantly improves. The performance of the modified coating shows the most significant improvement when the spindle speed reaches 1000 rpm. The study aims to explore the effect of spindle speed on the properties of alloy-modified layers produced by FSP without a stirring pin. This research could be used to create superior metal matrix composites by adding reinforcement particles.

Improvement of corrosion resistance and electrical conductivity of a Cr–C coated heat-assisted forming stainless steel bipolar plate for proton exchange membrane fuel cell

Heat-assisted forming is gaining increasing attention for its potential in improving the formability and quality of metallic bipolar plate (BPP) of proton exchange membrane fuel cell (PEMFC). However, the effects of heat-assisted forming and the subsequent coating process on corrosion resistance and electrical conductivity of stainless steel BPP still remain unclear. This work proposes a way to improve simultaneously the corrosion resistance and electrical conductivity of heat-assisted forming stainless steel BPP by depositing a Cr–C coating directly on its surface without removing the oxide layer using the magnetron sputtering method. Potentiodynamic tests indicate that self-corrosion current density and corrosion current density at 1.0 V (vs. Ag/AgCl) of the Cr–C coated heat-assisted forming SS316L BPP prepared under 900 °C for 10 min are 0.021–0.040 μA cm−2 and 77.54 μA cm−2, respectively, both of which are smaller than those of coated SS316L BPP formed under room temperature. In addition, the contact resistance is close to that of the gold-plated copper plate under the same pressure. The corrosion resistant intermediate oxide layer and conductive network formed between Cr–C coating and metal substrate through defects of oxide layer may be the main reason for improvement of its corrosion resistance and electrical conductivity, respectively.

Lithium nitrate salt-assisted CO2 absorption for the formation of corrosion barrier layer on AZ91D magnesium alloy.

Mg alloy corrosion susceptibility is a major issue that limits its wide industrial application in transport, energy and medical sectors. A corrosion-resistant layer containing crystalline MgCO3 was formed on the surface of AZ91D Mg alloy by Li salt loading and thermal CO2 treatment. Compared to the uncoated AZ91D surface, the surface layer exhibited up to a ∼15-fold increase in corrosion resistance according to the electrochemical results in 3.5 wt% NaCl solution and ∼32% decrease in wear rate compared to untreated AZ91D. The improved corrosion resistance is attributed to the formation of a <10 μm thick dense layer containing Mg, O, C and Li with crystalline MgCO3 phases. The initial step was to form a porous MgO layer on the surface of AZ91D Mg alloy, followed by loading an alkali metal salt (i.e., LiNO3) onto the MgO surface. The porous MgO surface was then reconstructed into a dense insulation layer containing Mg carbonate through CO2 absorption facilitated by molten Li salt during thermal CO2 treatment at 350 °C. As a potential method to utilize excessive CO2 for beneficial outcomes, the formation of the carbonate-containing film introduced in this study opens a new pathway for protecting various existing Mg alloys for diverse industrial applications.

Development of Fe–Cr–Si deposited layer manufactured by laser directed energy deposition process

In this study, the mechanical and corrosion characteristics of a corrosion-resistant layer made of stainless steel (STS) 316 L and Fe–Cr–Si alloy powder were investigated using laser-directed energy deposition (DED). In the STS 316 L deposited specimen, both the substrate and deposited layer were face-centred cubic (FCC). The deposited Fe–Cr–Si layer was clearly separated from the substrate because it was composed of body-centred cubic (BCC). Despite the phase differences, the surface of the Fe–Cr–Si-deposited layer showed a lower corrosion rate than that of the STS 316 L. All the deposited specimens exhibited typical high-temperature tensile behavior. However, the Fe–Cr–Si deposited layer at 600 °C showed a notable reduction in strength and increased elongation compared to the room temperature (RT) and 300 °C test results owing to the carbide concentration and phase transformation in the deposited layer. Because nuclear facilities mainly operate at temperatures below 600 °C, Fe–Cr–Si materials can also be used as nuclear piping coating materials. This study provides a mechanism for the high-temperature properties and corrosion resistance of the Fe–Cr–Si deposited layer and makes it competitive for application in fourth generation nuclear power systems.

Engineering dual MoC–Mo2C heterostructure–knotted CNTs for efficient direct seawater electrolysis

Considering the abundant reserves of seawater and limited resources of freshwater, seawater electrolysis is a more economically competitive technology for producing high-purity hydrogen, but remains a challenging approach. Herein, we report an innovative strategy for constructing dual MoC–Mo2C heterostructure–knotted CNTs nanorods (MoC–Mo2C/CNTs) to improve the electrocatalytic performance and durability in alkaline seawater, in which the hybrid electrode achieves 10 mA cm−2 at low overpotentials of 95 and 279 mV for HER and OER, respectively. For overall simulated and natural seawater splittings, a low cell voltage of 1.57 and 1.61 V, respectively, is necessary to drive 10 mA cm−2 and outstanding durability over 50 h at a high current density of 50 mA cm−2. The experimental results indicate that the unique boundary interface of MoC–Mo2C/CNTs could result in rich exposed active sites, corrosion resistance layer, and electronic redistribution, thus leading to high-performance HER and OER activities. This work provides an ultimate approach to the rational design of multi-component transition metal carbide-based heterogeneous electrocatalysts for seawater electrolysis.

Microstructure and corrosion resistance of 23Cr9Ni4Mo2Mn filler duplex stainless steel 2205 fabricated by wire arc additive manufacturing with subsequent severe shot peening and Ni58Cr20Fe5Mo10 plasma spray coating

In the current study, 23Cr9Ni4Mo2Mn (FeAs) filler and duplex stainless steel 2205 materials were used in multi-layer deposition processes for wire arc additive manufacturing (WAAM) process. The WAAM samples were prepared with WAAM coated (WAAM-C) and Post-shot peening coated WAAM (PSPC-WAAM) in order to improve the microstructure and surface properties. The severe shot peening process and Ni58Cr20Fe5Mo10 plasma spray coating was increase the corrosion resistance and outer layer strength, whereas different types of structure were observed in the WAAM-DSS plates: Solid phase martensite (SPM), acicular austenite phase (AAS), FeCr2O4, martensite-austensite phase (MAP) and multi-phase ferrite structure. The severe shot peening procedure and Ni58Cr20Fe5Mo10 plasma spray coating samples were clearly visible in the Electron Backscatter Diffraction (EBSD) analyses, which also showed that the outer and inner surface layers of the samples contained CrFe2O4, NiFe2O4 cubic ferromagnetic oxide, and BiFeO3 phase. Direct mixing of the 23Cr9Ni4Mo2Mn filler with the base materials produced a homogenous structure with a high bonding strength. Bi1<001>, Bi2<111>, and Bi3<110> of the BiFeO3 crystal structure were discovered in the inner surface layer according to the PSPC-WAAM sample of angle 0–1800 texture results, whereas the WAAM-C sample of the outer layer revealed that As1<001>, As2 < 100>, and As3 < 111> of the α-martensite structure were exposed at the outer surface layer. PSPC-WAAM had a 6 % increase in hardness over WAAM-C in both the inner and outer surface regions. Hardness value of PSPC-WAAM was 286 HV on NiCr bulk structure demanded, whereas ferrite secondary phase of WAAM-C have increased the hardness value at 224 HV compared to the base materials. Both the PSPC-WAAM and WAAM-C samples achieved improved corrosion resistance and strong surface bonding. The WAAM, WAAM-C, and PSPC-WAAM samples were the subject of potential dynamic experiments, AFM and wear properties.

A high corrosion resistant Fe-VC layer laser cladded under water-cooled substrate condition

Nano VC reinforced submicron Fe-based composite cladding layers were successfully obtained under water-cooled substrate conditions, showing an absence of noticeable defects. The matrix of the layer mainly consisted of equiaxed grains, with the average grain size refined to 0.78 μm. The VC with an average particle size of 72 nm distributed along the grain boundaries. As a result, the hardness of the layer increased from 225 HV0.2 to 930 HV0.2. Additionally, the cladding layer exhibited prominent passivation characteristics, its corrosion resistance was comparable to that of the 2Cr13 stainless steel.

Corrosion behaviour of hot-rolled 316L stainless steel-A6 carbon steel composite steel plate for marine environment

In this study, a composite steel plate for marine construction was fabricated using 316L stainless steel and A6 carbon steel through hot rolling. Neutral salt spray tests and electrochemical experiments were performed to analyse the corrosion behaviours of the cladding material, the carbon steel substrate, and the interface between stainless steel and carbon steel in a marine atmosphere and seawater. The results showed that an evident elemental overlap region was observed at the composite interface of the composite steel plate. After long salt spray test, the A6 carbon steel part showed significant accelerated corrosion along the interface, resulting in the interface specimens corroding at a faster rate than the carbon steel substrate. However, the composite interface showed better corrosion resistance than the carbon steel substrate in the electrochemical tests. A corrosion resistant layer with a width of 15 μm was found on the stainless-steel side of the composite interface.

Effects of elevated temperature exposure on the residual stress state and microstructure of PVD Cr coatings on SiC investigated via in situ X-ray diffraction and transmission electron microscopy

Pure Cr coatings are being considered as corrosion-resistant layers for SiC-SiCf composite fuel cladding in light water reactors. The residual stress state and interdiffusion behavior of Cr coatings deposited on SiC substrates using bipolar high-power impulse magnetron sputtering (B-HiPIMS) and direct current impulse magnetron sputtering (DCMS) were studied using in situ X-ray diffraction experiments at 300 °C, 700 °C, and 1200 °C. After elevated temperature exposure, evolution of the coating microstructure and coating/substrate interdiffusion was characterized by transmission electron microscopy. The compressive residual stress of the dense B-HiPIMS coating at room temperature was gradually relieved at 300 °C, while the stress transitioned to a tensile state at 700 °C. Grain growth of the Cr coating and a Cr–SiC interdiffusion layer consisting of newly formed Cr–C and Cr–Si phases were observed in the B-HiPIMS coating after exposure at 700 °C. The phases in the interdiffusion layer were identified to be Cr7C3, Cr3Si, and Cr5Si3Cx experimentally and by thermodynamic predictions. For the DCMS coating, however, changes in residual stress and microstructure at the elevated temperatures were limited by the inherent porosity and inhomogeneous structure of the as-deposited coating. At 1200 °C, both coating types interacted rapidly with the underlying SiC substrate in the early stages of the experiment. The results from this study suggest that the characteristics of the Cr coatings do not significantly change at the reactor operating temperature of 300 °C, while changes in microstructure and stress state are expected in off-normal conditions of 700 °C and 1200 °C. The results from this study suggest the B-HiPIMS coating is best-suited as a protective coating for SiC fuel cladding.

Biodegradable Mg alloy modified with bioactive exosomes for cardiovascular stent application

Cardiovascular stent has been widely applied to treat cardiovascular disease (CVD), which is the major disease contribution to mortality in the world wide. Biodegradable magnesium (Mg) alloys are the encouraging materials in cardiovascular stents benefit from absorbability and biocompatibility. While, the ability of degradation is a double-edged sword for manufacture stent, modifying the surface to decrease the excessive degradation rate and promote the surface endothelialization could expand the prospect of the further application. In this work, the biodegradable Mg-Zn-Y-Nd alloy was modified by MgF2 and dopamine polymer film (PDA) as the corrosion resistance layer and the bonding layer respectively, and then the exosome, a natural nanoparticle contains mRNAs and proteins, was tailored to give the surface better biocompatibility. The electrochemical test and weight loss test reflected the MgF2-PDA/exosome coating increase the corrosion resistance of the Mg-Zn-Y-Nd alloy. The cytocompatibility data indicated the novel MgF2-PDA/exosome coating selectively reduced the tumor necrosis factor (TNF-α) expression and ROS release from macrophage, and promoted the α-SMA expression of smooth muscle cells. In addition, the MgF2-PDA/exosome coating also improved the adhesion, proliferation, CD31 expression and nitric oxide (NO) release of vascular endothelial cells (ECs), all of which contribute to the surface endothelialization. And the mechanism experiments showed the exosome released from the coating uptake by the ECs and assemble around the lysosome and mitochondria, and the released rate of the exosome on the coating is around 5 to7 days, indicating excellent multi-functions of MgF2-PDA/exosome coating in cardiovascular stent.

New protective coatings against liquid zinc corrosion

Hot dip galvanizing is a surface treatment used to form a corrosion-resistant layer on the surface of steel by dipping it in a liquid zinc bath. However, a lot of structures used for hanging or containing the parts during the process are made of steel and suffer from liquid zinc corrosion. Furthermore, Fe–Zn intermetallics formed on the surface induce an additional pickling and zinc consummation, therefore generating supplementary economic and environmental costs. In this article, two Fe-Cr-Ni-Si coatings synthetized by the slurry process on carbon steel (C22) were characterized by XRD, EDX, EPMA and EBSD analyses. Their corrosion protective properties were studied in the process imitating cyclic batch galvanizing and compared to those of uncoated carbon steel (C22) and stainless steel (316 L). The coatings were verified to be more efficient than the 316 L steel usually used for this application. After 9 cycles of no weight loss, molten zinc corrosion was linear and the same for Fe-Cr-Ni-Si coatings as for the stainless steel.

Effect of surface preparation by high-temperature hydrogen annealing on the passivation of Ni-20 at.% Cr alloy in sulfuric acid

The effect of high-temperature annealing under hydrogen gas (H2) surface preparation on a binary polycrystalline Ni-20 at.% Cr alloy was investigated in comparison with conventional mechanical grinding surface preparation. Duplex surface films with inner Cr(III) oxide and outer Ni(II) and Cr(III) hydroxide layers natively formed before and after H2 annealing were characterized by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy. A thinner and less homogeneous inner barrier layer formed after H2 annealing caused an oxidation peak at the active/passive transition in the linear sweep voltammetry measurement in a 0.5 M H2SO4 solution. Despite this high oxidation peak, passivation of the H2 annealed surface resulted in the formation of a more corrosion resistant inner layer than on the mechanically ground surface, as demonstrated by electrochemical impedance spectroscopy. The corrosion resistant passive film formation of the H2 annealed surface is attributed to the increased Cr enrichment of the inner layer caused by the selective Ni dissolution providing corrosion resistance to the initially weakly protected sites of the natively formed surface film.

Argon arc surfacing with high corrosion resistance on inner cylindrical surface of forgings made of low-alloy steel of strength class 85K

The procedure of surfacing a corrosion-resistant layer on low-alloy steel treated according to the adjusted heat treatment regime is considered and macro- and microanalysis of the structure of the base metal, the fusion line and the surfacing metal are carried out. Using the original computer program of the author of the article, the tendency of the deposited system to crack formation is estimated.

Photoelectric properties of the layered raspberry sandwich amorphous ZnCo2S4@MnCo2S4/CP composite counter electrode in semiconductor-sensitized solar cells.

Multistage amorphous materials have promising applications in the catalytic performance of dye-sensitized solar cells (DSSCs). Herein, an amorphous sheet-raspberry sandwich-like ZnCo2S4@MnCo2S4/CP composite material was rationally designed and developed as a counter electrode (CE) for DSSCs by applying a three-step hydrothermal method. The first development of the amorphous composites as CEs resulted in lower charge transfer resistance at the CE/electrolyte interface and improved the fill factor and short-circuit current density. The excellent catalytic performance is mainly attributed to the large number of unsaturated coordination sites generated by the undirected structure of the lamellar-raspberry intercalated amorphous material, the smooth ion transport interface with a self-built corrosion-resistant layer, coupled with the dual catalytic performance of the Zn, Co, and Mn composites, and the good electrical conductivity of the C substrate. When ZnCo2S4@MnCo2S4/CP was used as the CE on a Ti substrate, the photoelectric conversion efficiency was as high as 11.68% (Voc = 0.821, Jsc = 20.14 mA cm-2, and FF = 0.71) under 100 mW cm-2 light illumination. This paper provides a design idea for amorphous materials in terms of catalytic performance and a method for developing alternatives to Pt electrodes.

Effect of heat treatment on corrosion behaviour of additively manufactured 316L stainless steel in high-temperature water

Post-manufacturing heat treatment (PMHT) effect on the corrosion behaviour of directed energy deposition (DED) 316L stainless steel was investigated in hydrogenated water at 325 °C. As-DEDed and residual stress relief PMHTed (850 °C/2 h) specimens exhibited similar corrosion resistance, showing thick and thin inner oxide layer on the Cr-depleted cell interior and Cr-rich cell boundary, respectively. Composition homogenization PMHTed (1150 °C/1 h) specimen showed the best corrosion resistance with the much thinner inner oxide layer. The enhanced corrosion resistance of the PMHTed DED 316L than wrought 316L could be related to the unique large grain in DED 316L.

Influence of sodium 5-sulfosalicylate as a corrosion inhibitor in NaCl electrolyte on enhanced performances of Mg-air batteries

This work aims at employing sodium 5-sulfosalicylate (5-S-Sal) corrosion inhibitor into aqueous NaCl electrolyte to improve the discharge performance of Mg-air battery and decrease the side reactions of Mg anode. The corrosion tests at open circuit potential show a four-fold decrease of hydrogen evolution when 5-S-Sal inhibitor is added. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry analyses show that due to the presence of 5-S-Sal inhibitor, a corrosion resistant layer has a lower quantity of Mg(OH)2 (by ∼15%) than that formed in NaCl electrolyte. The surface enrichment in S-like species originating from inhibitor molecule could have an important effect on a decreased corrosion and slow down the H2 evolution. Within a range of concentrations of 5-S-Sal in NaCl electrolyte (0.05 to 0.15 M), the best discharge performances are achieved with 0.1 M inhibitor. The discharge voltage of full Mg-air battery improves from ∼1.58 to ∼1.82 V at 0.5 mA/cm2 and the discharge lifetime is extended from around 12.5 to around 80 h. Scanning electron microscopy and 3D topography laser microscopy indicate that during the discharge tests much smaller surface degradation occurs and a more uniform surface layer is formed in the presence of inhibitor in the NaCl-based electrolyte.

Role of SnO2 Nanoparticles for a Self-Forming Barrier Layer on a Mild Steel Surface in Hydrochloric Acid Medium Containing Piper betle Leaf Extract.

The self-formation of a porous organic thin-film via corrosion inhibitor supports wide applications of carbon steel in industry. Unfortunately, serious damages could be concentrated to the pinhole and/or pore locations in the porous organic film, resulting in the localized corrosion even when an optimal concentration of organic corrosion inhibitors is used. In this work, SnO2 nanoparticles are used for producing the more robust barrier layer via the self-migration of nanoparticles, resulting in a higher corrosion resistance, smooth and uniform protective layer, as well as the existence of SnO2 in the protective layer that could directly affect the high inhibition performance. Therefore, the work suggests a new way to make a more robust thin film that could extend the use of organic corrosion inhibitors.

A multi-functional MgF2/polydopamine/hyaluronan-astaxanthin coating on the biodegradable ZE21B alloy with better corrosion resistance and biocompatibility for cardiovascular application

The cardiovascular diseases (CVD) continue to be the major threat to global public health over the years, while one of the effective methods to treat CVD is stent intervention. Biomedical magnesium (Mg) alloys have great potential applications in cardiovascular stents benefit from their excellent biodegradability and absorbability. However, excessive degradation rate and the delayed surface endothelialization still limit their further application. In this study, we modified a Mg-Zn-Y-Nd alloy (ZE21B) by preparing MgF2 as the corrosion resistance layer, the dopamine polymer film (PDA) as the bonding layer, and hyaluronic acid (HA) loaded astaxanthin (ASTA) as an important layer to directing the cardiovascular cells fate. The electrochemical test results showed that the MgF2/PDA/HA-ASTA coating improved the corrosion resistance of ZE21B. The cytocompatibility experiments also demonstrated that this novel composite coating also selectively promoted endothelial cells proliferation, inhibited hyperproliferation of smooth muscle cells and adhesion of macrophages. Compared with the HA-loaded rapamycin (RAPA) coating, our MgF2/PDA/HA-ASTA coating showed better blood compatibility and cytocompatibility, indicating stronger multi-functions for the ZE21B alloy on cardiovascular application.

Preparation and CMAS Wettability Investigation of CMAS Corrosion Resistant Protective Layer with Micro-Nano Double Scale Structure

Solution precursor plasma spray (SPPS) can prepare thermal barrier coatings (TBCs) with nanostructures, which can modify the adhesion and wettability of molten silicate environmental deposits (CMAS) on the surface of TBCs, thereby improving the resistance of TBCs to CMAS corrosion. In this study, SPPS layers with micro-nano double scale structures were prepared on the surface of conventional atmospheric plasma spraying (APS) coatings. The effect of process parameters on the micro-nano double scale structures and the wetting and infiltration behavior of molten CMAS on the surface of coatings were investigated. The results show that micron structure is more sensitive to process parameters. Lower precursor viscosity, closer spraying distance, and smoother APS layer are favorable to form more typical and dense micron structures. After covering the SPPS layer, the CMAS wetting diameter is reduced by about 40% and the steady-state contact angle increased up to three times. The reason is that the micro-nano double scale structures can effectively trap air and form an air layer between the coating surface and the molten CMAS. In addition, nano-particles play a more important role in the formation of the air layer, which in turn determines the steady-state wettability properties. While micron structures can influence the time needed to reach the steady state. However, the SPPS layers composed of nano-particles have a very loose structure and weak cohesion, and they degrade and fail rapidly after the infiltration of molten CMAS. Therefore, maintaining the excellent CMAS wetting resistance of the SPPS layers while taking into account their lifetime and reliability has become the focus of further research.

Obtaining a high-nickel-alloyed layer on the surface of low-carbon steel using monometallic powders and laser processing

The paper studies deposition of a highly nickel-alloyed corrosion-resistant layer on the surface of a low-carbon economically alloyed steel. The formation of the layer is carried out in two stages – at the first stage, a precursor coating is applied by cold spraying, and at the second, an alloyed layer is formed on the surface by laser. A layer with a nickel content of up to 70% is formed on the surface of the steel. The results of X-ray diffraction phase analysis indicate that a face-centered cubic lattice of a solid solution and Ni3Fe intermetallic compound has been formed in the studied layer.