Decrease In Corrosion Resistance Research Articles

Dissolution and redistribution behavior of Cu-rich phase: Implications for corrosion resistance in Cu-bearing duplex stainless steel in chloride media

In this study, the dissolution and redistribution behaviors of the Cu-rich phases were investigated to determine their effect on the corrosion resistance of Cu-bearing 2205 duplex stainless steels. This investigation revealed the presence of Cu-rich phases with varying precipitation modes in ferrite and austenite, as well as a decrease in corrosion resistance as their size increased. The Cu-rich precipitate was preferentially dissolved compared to the steel matrix. A corrosion-product layer was formed on the surface of the alloy. The Volta potential difference between the Cu-bearing corrosion products and the matrix was lower than that between the Cu-rich phase and the matrix. This reduction in the potential difference enhanced the corrosion/passive film stability and improved the corrosion resistance of the alloy.

Improved Ability to Resist Corrosion of Selective-Laser-Melted Stainless Steel Based on Microstructure and Passivation Film Characteristics

The local corrosion resistance of forging and selective laser melting (SLM) 304 steels was explored by intergranular corrosion analysis, double-loop electrochemical potentiodynamic reactivation, dynamic polarization experimentation, structural analysis, and passivation film characteristics analysis. The ability to resist sensitization of SLM 304 steel is greater than that of forging 304 steel at a temperature of 650 °C for 9 h. Moreover, the pit corrosion resistance of forging and SLM 304 steels is weakened by sensitization, while the pit corrosion resistance of SLM 304 steel is much greater than that of forging steel. Therefore, SLM technology can improve the ability to resist sensitization and pit corrosion of 304 steel. Analysis showed that the ability to resist corrosion of the passivation film of SLM 304 steel is greater than that of forging steel. In addition, corrosion pits are easier to generate at the interface of forging steel and SLM 304 steel. The grain boundary corrosion of SLM 304 steel intensified while the corrosion of the melt pool boundaries weakened after the sensitization treatment, resulting in a decrease in pit corrosion resistance. The coupling effect of these different structures and passivation films decides the pit and sensitization resistance of forging and SLM 304 steels. Clarifying the corrosion mechanism of forging and SLM steels is of great significance for scientific research and the widespread use of SLM technology.

Effect of adding K2TiF6 and K2ZrF6 to neutral electrolyte on the performance of plasma electrolytic oxidation coatings on AZ91 Mg alloy

The traditional alkaline electrolyte preparation of plasma electrolytic oxidation (PEO) coating ignites a significant spark, and the increase of micro-defects leads to a decrease in corrosion resistance. In this study, the preparation of PEO coating with neutral electrolyte was studied, and the effects of K2TiF6 and K2ZrF6 doping on the microstructure, phase composition, corrosion resistance and mechanical properties of the coating were explored. It was found that in neutral solution, the size and number of sparks decreased significantly, and the compactness of the coating increased. The phase composition was mainly MgF2. After the addition of K2TiF6 and K2ZrF6, the corrosion current density dropped from 256 to 28 and 61 nA/cm2. The long-term corrosion resistance of the coating was significantly improved. The hardness and adhesion of the coating were significantly improved.

Corrosion resistance of Cu-Fe deformation processed in situ alloy in chloride ion environment

To assess the corrosion resistance of Cu-Fe deformation in situ alloys in a chloride ion environment, Cu-Fe alloys with varying Fe contents (5 wt%, 10 wt%, and 14 wt%) were prepared using vacuum induction melting, and the impact of Fe content on the corrosion resistance was examined. The corrosion morphology and corrosion products were analyzed, and the corrosion rate, corrosion period, dynamic potential polarization curves, electrochemical parameters, and electrochemical impedance spectra with different Fe contents were determined. However, the corrosion resistance of Cu-Fe alloys initially increased with an increase in Fe content before decreasing, with Cu-10 wt% Fe alloys (95% reduction rate) exhibiting the best corrosion resistance. As the Fe content increased, the amount of primary Fe phase gradually increased and became more densely distributed. This led to an increase in the dense oxide film on the surface, thereby enhancing the corrosion resistance of the material. Moreover, with a further increase in Fe, the primary Fe phase exhibited coarsening and non-uniform distribution. This resulted in the oxide film becoming looser, leading to a decreased corrosion resistance of the alloy.

Shot peening of AZ31 magnesium alloy: role of surface microstructure and iron diffusion on corrosion behaviour

ABSTRACT In the present work, surface grain refined AZ31 magnesium (Mg) alloy was produced by shot peening (SP). X-ray diffraction analysis demonstrated iron diffusion into the surface of AZ31 Mg alloy during SP. Higher hardness, increased surface energy and decreased corrosion resistance were observed for the shot-peened surface due to nanostructured grains resulted from SP. From the immersion studies in a simulated physiological solution carried out for 3 days, higher level of biomineralization was observed for the shot peened AZ31 compared with the base alloy that dominated the adverse effect of iron diffusion in resisting the biocorrosion. The results suggest that the nano-structuring of AZ31 Mg alloy surface helps to enhance the biomineralization to control the degradation. However, the selection of processing medium is crucial to eliminate the effect of chemical composition change during the process in tailoring the corrosion behaviour of AZ31 Mg alloy for biomedical implant applications.

Effect of pool temperature on microstructure and corrosion resistance of PTAW Ni layer

In plasma transferred arc welding (PTAW), the weld pool temperature often fluctuates. The spray weld layer is prone to overheating, leading to adverse effect on its performance. This study investigated the influence of spray welding current on the weld pool temperature and in turn on the microstructure, microhardness and corrosion resistance of the PTAW-Ni layer on a steel substrate. Weld pool temperature increased with increasing spray welding current and varied along the welding gun path before reaching the steady state. With increasing pool temperature, more Fe diffused from the substrate into the spray weld layer, leading to a widened fusion zone, an increased dilution rate and a decreased microhardness. The spray weld layer has a dendritic microstructure. The dendrites have a higher Cr content, while the interdendritic regions have a higher Ni content. Increasing weld pool temperature increased diffusion, resulting in reduced enrichment of the Cr and Ni elements. The increase of Fe and decrease of Cr in the spray weld layer caused the decreasing corrosion resistance.

A comparative study on resistance spot and laser beam spot welding of ultra-high strength steel for automotive applications

In this study, the effect of resistance spot welding (RSW) and laser beam spot welding (LBSW) processes on evolution of microstructure, load endurance capabilities, heat affected zone (HAZ) softening, and corrosion resistance of ultra-high-strength (UHSS) steel joints welded in lap joint design is investigated. The UHSS sheets of dual phase 1000 grade (UHSDP1000) having 1.20 mm thickness were joined using the RSW and LBSW parameters optimized by response surface methodology (RSM). The microstructural features of welding regions of RSW and LBSW joints were studied using optical microscopy (OM). The load endurance capabilities of RSW and LBSW joints were assessed using the tensile shear failure load (TSFL) and cross-tensile failure load (CTFL) tests. The ruptured surfaces of TSFL and CTFL tested samples were examined utilizing scanning electron microscopy (SEM). The microhardness distribution of divergent regions of RSW and LBSW joints was evaluated and imputed to the TSFL and CTFL failure of joints. The corrosion resistance of RSW and LBSW joints was analyzed using potentiodynamic corrosion and immersion corrosion tests. The RSW joints showed 183% and 62.79% greater TSFL and CTFL endurance capabilities than LBSW joints. The TSFL and CTFL endurance capabilities of LBSW joints are inferior to RSW joints due to the smaller load bearing area. It causes the stress concentration in FZ and HAZ of LBSW joints. The RSW joints and LBSW joints disclosed TSFL and CTFL failure in button pull out rupture mode with tearing of HAZ. The failure of RSW and LBSW joints in HAZ is due to the softening caused by martensitic tempering and coarsening of grains. The LBSW joints disclosed inferior resistance to corrosion than RSW joints due to the higher martensite content which contributes to greater fraction of favorable pitting sites and decreased corrosion resistance.

Microstructure and Corrosion of Mg-Based Composites Produced from Custom-Made Powders of AZ31 and Ti6Al4V via Pulse Plasma Sintering.

Magnesium (Mg) and its alloys offer promise for aerospace, railway, and 3D technology applications, yet their inherent limitations, including inadequate strength, pose challenges. Magnesium matrix composites, particularly with metallic reinforcements like titanium (Ti) and its alloys, present a viable solution. Therefore, this study investigates the impact of Ti6Al4V reinforcement on AZ31 magnesium alloy composites produced using pulse plasma sintering (PPS). Results show enhanced microhardness of the materials due to improved densification and microstructural refinement. However, Ti6Al4V addition decreased corrosion resistance, leading to strong microgalvanic corrosion and substrate dissolution. Understanding these effects is crucial for designing Mg-based materials for industries like petrochemicals, where degradation-resistant materials are vital for high-pressure environments. This research provides valuable insights into developing Mg-Ti6Al4V composites with tailored properties for diverse industrial applications, highlighting the importance of considering corrosion behavior in material design. Further investigation is warranted to establish predictive correlations between Ti6Al4V content and corrosion rate for optimizing composite performance.

Effect of quenching and tempering on microstructure and corrosion resistance of aerospace-bearing steel

CSS-42L steel is not only highly competitive for aerospace bearing applications but also for core components such as gears and shafts used in high-temperature or corrosive environments. This puts higher requirements on its microstructure, mechanical properties, and corrosion resistance. In this paper, CSS-42L steel was subjected to quenching, cryogenic and tempering treatments to study the effects of different heat treatments on the microstructure, hardness, and corrosion resistance of CSS-42L steel. It was found that the microstructure of the specimen after quenching contained martensite, a large amount of residual austenite, and trace amounts of fine carbides, and its hardness and corrosion resistance were improved. The residual austenite in the tempered sample underwent almost complete decomposition and transformed into fine martensite, and numerous finely dispersed and uniformly distributed carbides were precipitated, its hardness was further increased to 578.6 Hv concerning the quenched specimen, but concurrently exhibited a decrease in corrosion resistance. CSS-42L steel can be hardened by quenching, cryogenic and tempering to obtain martensite, but fine martensite reduces corrosion resistance. Since the amount of martensite or residual austenite affects the mechanical properties and corrosion resistance of CSS-42L bearing steel, the ratio of martensite and residual austenite needs to be adjusted to obtain optimum mechanical properties and corrosion resistance.

Effect of V Content on Corrosion Behavior of Al-V Alloys Produced by Mechanical Alloying and Subsequent Spark Plasma Sintering

Abstract Al-V alloys produced via high-energy ball milling have been reported to show simultaneous improvement of corrosion resistance and mechanical properties compared to traditional Al alloys. In these alloys, V content plays a crucial role in increasing or decreasing corrosion resistance. Therefore, the effect of V and microstructure on corrosion of high-energy ball milled and subsequently spark plasma sintered Al-xV alloys (x = 2, 5, 10 at.%) has been studied. Cyclic potentiodynamic polarization tests and electrochemical impedance spectroscopic analysis revealed that increments of V content up to 5 at. % enhanced the corrosion resistance of the alloy. However, highly heterogeneous microstructure in Al-10 at.%V resulted in significant localized corrosion over the immersion time. The electrochemical impedance spectroscopy studies over 14 days of immersion revealed underlying corrosion mechanisms.

Corrosion resistance of the modified surface of AISI 316L steel

The paper is devoted to the study of the effect of laser processing on the wettability and corrosion resistance of the surface of experimental samples made of AISI 316L sheet steel and samples made by printing from AISI 316L steel powder using selective laser melting technology. As a result of the studies, it was established that laser texturing of the relief with the subsequent formation of molecular layers of surfactants on a steel surface helps to achieve higher contact angle values, however, such treatment leads to a decrease in corrosion resistance.

Polysilazane-derived SiON coating on stainless steel weld for corrosion resistance

In this study, SiON coatings were created using perhydropolysilazane (PHPS) on the weld region and the base stainless steel region with different microstructure and composition. The influences of the weld and base steel compositions and microstructures on coating formation, composition, microstructure, mechanical properties, and corrosion resistance are discussed. The SiON coatings show a higher N content and a lower O content on the base metal than on the weld metal. Salt spray tests show that the differences in mechanical properties and compositions on the weld and base steel substrates do not significantly affect the function of the corrosion-protective coatings. However, when the coating thickness is high, the corrosion resistance decreases. This study provides important guidance regarding the desirable SiON coating and thickness for best corrosion prevention.

Investigation of Spinodal Decomposition in Isothermally Heat Treated LDX 2101 type Duplex Stainless Steel at 475 °C

Spinodal decomposition of the ferritic phase, a thermally induced phase transformation process is studied in an LDX 2101 type lean-duplex stainless steel by different examination methods. This phase transformation in duplex stainless steels has special importance because it is responsible for the so called "475 °C embrittlement". This deterioration process causes a decrease in toughness and corrosion resistance. Fe-Cr alloys, thus several stainless steels, are susceptible to the spinodal decomposition at intermediate and low temperatures (<600 °C). Therefore, it is important to study this phenomenon in novel lean-duplex stainless steels as well. Our results revealed that spinodal decomposition occurs to a lesser extent in the studied type of lean-duplex stainless steel but its effect is not negligible in applications.

Effect of sterilization on the corrosion behavior of orthopedic implants coated and uncoated

The impact of sterilization on the corrosion behavior of orthopedic implants produced via Laser Powder Bed Fusion is analyzed in a biologically relevant environment. In a controlled environment at 37 °C, experiments were conducted to mimic a natural biological state. In a controlled oven at 50 °C for 20 min, AISI 316L stainless steel samples were prepped before primary testing. The experiment showed that sterilization leads to the development of a more efficient passive layer, resulting in improved corrosion resistance. The improvement in corrosion potential, pitting potential, and corrosion rate was substantial. A decrease in corrosion resistance is observed when TiN (Titanium Nitride) is applied. The findings suggest that sterilization can enhance the corrosion performance of 316L L-PBF implants, although this improvement may not apply equally to all coated components, such as those with TiN coatings.

Issledovanie prochnosti, relaksatsionnoy i korrozionnoy stoykosti ul'tramelkozernistoy austenitnoy stali 08Kh18N10T, poluchennoy metodom RKU-pressovaniya. II. issledovanie relaksatsionnykh svoystv i stoykosti protiv mezhkristallitnoy korrozii

Relaxation resistance and corrosion resistance of samples of ultrafine-grained steel 08H18N10T obtained by the method of equal-channel angular pressing at temperatures of 150 and 450 °C are investigated. For ultrafine-grained steel with high values of the limit of macroelasticity and yield strength, a decrease in the Hall—Petch coefficient due to fragmentation of δ-ferrite particles at the method of equal-channel angular pressing is shown. It is established that the samples of ultrafine-grained steel have 2-3 times higher relaxation resistance compared to coarse-grained steel. It is noted that the method of equal-channel angular pressing leads to an increase in the rate of general corrosion. At the same time, despite the decrease in corrosion resistance, samples of ultrafine-grained steels have high resistance to intercrystalline corrosion. It is established that the decrease in corrosion resistance of ultrafine-grained steel is due to an increase in the volume fraction of martensite deformation at the method of equal-channel angular pressing.

Investigating the role of processing temperature on the microstructure evolution, mechanical properties, and corrosion behaviour of equal channel angular pressed AZ31 Mg alloy

AZ31 magnesium (Mg) alloy was subjected to equal channel angular pressing (ECAP) through Bc route at three different temperatures (200, 250 and 300 °C) to investigate the role of processing temperature on the microstructure evolution. All the sample were processed for one complete cycle which includes 4 consecutive pressings. Workpiece processed at 200 °C has shown relatively higher grain refinement (2.1 ± 1.4 μm) compared with the samples processed at 250 °C (5.6 ± 2.7 μm) and 300 °C (7 ± 5.5 μm) from a starting size of 36 ± 4.1 μm. Increased hardness was measured for the ECAPed samples at 200 °C due to the higher level of grain refinement. Workpiece produced at 200 °C exhibited higher tensile strength (270.9 ± 6.3 MPa) compared with the other processed samples and base alloy. Surface energy measurements from the contact angles show the positive effect of grain refinement on increasing the hydrophilic nature of AZ31 alloy. Corrosion experiments from the potentiodynamic polarization studies demonstrate lower corrosion current for the base alloy compared with all of the processed alloys. The deteriorated corrosion performance in the ECAPed alloys can be claimed to the increased crystal imperfections due to ECAP. From the results, it is understood that the lower processing temperatures are preferable to achieve higher level of grain refinement in ECAP of AZ31 Mg alloy. Excellent mechanical properties can be achieved in AZ31 alloy by ECAP and the decreased corrosion resistance is a concern to pay more attention.

Mechanistic analysis of improving the corrosion performance of MAO coatings on Ti-6Al-4V alloys by annealing

Titanium and its alloys find extensive application within the realms of dentistry and orthopedics due to their remarkable chemical stability. Nevertheless, they are still susceptible to corrosion in harsh environments. Micro-arc oxidation (MAO) emerges as a potent methodology for enhancing the corrosion resistance of titanium and its alloys, achieved through the generation of a ceramic stratum atop the material's surface. The corrosion resistance of MAO coatings in clinical applications is closely related to their microstructure. This manuscript systematically explores the effect of annealing temperature on the phase composition and microstructure of MAO coatings. Furthermore, the evolution of the surface properties and the crystal structure of coatings is meticulously discussed and illustrated. The results show that the corrosion resistance of coatings exhibits an ascending trajectory followed by a subsequent decline, coinciding with the augmentation of the annealing temperature. This behavior can be attributed to the structural evolution of coatings caused by the gradual increase of the annealing temperature. At the optimum temperature (400 °C), the annealing treatment leads to the crystallization of the coating as well as to a decrease in the surface porosity, resulting in the formation of a compact and continuous multilayer microstructure. The decrease in porosity can be attributed to the diffusion-reaction of oxygen from the air with titanium from the discharge channel (titanium oxide), resulting in the formation of TiO2 particles that effectively fill the pores. The decrease in corrosion resistance of the coatings after annealing at 800 °C is due to the phase transition of TiO2 which leads to the expansion of cracks inherent in the oxide layer to form A-H cracks. Therefore, this study shows that the microstructure of MAO coatings can be adjusted by post annealing treatment (400 °C) to obtain a desirable oxide layer with appropriate porosity, crystallinity and chemical composition, thus improving its corrosion resistance.

Microstructure, properties and natural ageing behavior of friction stir welded dual-phase Mg-Li alloy

In this study, the super-light α + β dual-phase Mg-9Li-3Al-3Zn alloy was successfully jointed by friction stir welding (FSW). The microstructure, mechanical properties as well as corrosion resistance of the welds were specially explored. The natural age-softening of the welds was found and the underlying mechanism for the properties durability was revealed. FSW resulted in significant grain refinement as well as dissolution of α-Mg phases into β-Li phases in the stirred zone (SZ). Meanwhile, Mg17Al12 (λ) and AlLi (γ) precipitates were dissolved into the matrix while orderly-arranged MgLi2Al (θ) precipitates were formed, which contributed to a precipitation-strengthening effect. Therefore, the welds exhibited extensive hardening and demonstrated superior tensile strength than base metal (BM). Under the optimal welding parameters, the ultimate tensile strength (UTS) of the weld reached 165.8% of that of the BM. On the other hand, the welds obtained at the various rotation speeds also exhibited lower corrosion rates than that of the BM, and higher rotation speeds led to superior corrosion resistance. Furthermore, owing to increase in γ precipitate content during natural ageing, the precipitation-strengthening effect in the weld was weakened, resulting in reduction of the strength of the welds. Meanwhile, the increasing γ precipitate content aggravated the local micro-galvanic coupling corrosion, causing the decrease in corrosion resistance of the welds during natural ageing. This welding method might be useful for obtaining the dual-phase Mg-Li alloys with high mechanical properties and corrosion resistance.

Effects of minor alloying elements (Si, Mn and Al) on the corrosion behavior of stainless steels in molten carbonate fuel cell cathode environment

Abstract Effects of minor alloying elements (Si, Mn, and Al) on the corrosion resistance behaviors of stainless steel (SS) modified 310S used as a cathode current collector (CCC) material for molten carbonate fuel cells (MCFC) were examined in a mixture of 62 mol% Li2CO3–38 mol% K2CO3 at 650 °C by measuring the change in corrosion potential and the potentio-dynamic, potentio-static polarization responses. The corrosion potential of modified 310S gradually increased after 9 h of immersion due to an active to passive transition and that of SSs added with minor alloying elements drastically increased before 6 h of immersion due to the reactive alloys. Si, Mn, and Al addition to base SS led to a decrease in corrosion resistance due to the rapid corrosion rate at the cathode operation potential, −40 mV, of the MCFC. The steady state current densities of SSs added with minor alloying elements were higher than that of 310S and modified 310S. Addition of Si, Mn, and Al induced a decrease in corrosion resistance of CCC materials in molten carbonate fuel cell operating temperatures, 650 °C.

Effect of aging temperature on corrosion resistance of 316L stainless steel in simulated proton exchange membrane fuel cell cathode environment

The effects of aging temperature on the corrosion behavior of 316 L stainless steel in a simulated cathodic environment of a proton exchange membrane fuel cell (PEMFC) were investigated by potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), double-loop electrochemical potential response (DL-EPR). The results show that the corrosion resistance of 316 L is significantly degraded after aging at 750–900 °C for 1 h in the simulated cathodic environment of PEMFC. A strong sensitivity to intergranular corrosion takes place after aging at 850 °C, and chromium rich M23C6 carbides precipitate on grain boundaries. The precipitation of M23C6 leads to discontinuity of the passivation film near the grain boundaries, resulting in Cr-depleted zones at the grain boundaries, increasing intergranular corrosion, and decreasing corrosion resistance. When the aging temperature exceeds 950 °C, grain boundary precipitation of M23C6 does not occur and the corrosion resistance is improved. At an aging temperature of 1050 °C, a dense Cr2O3 film is formed on the surface of the alloy during the polarization test, giving it the best corrosion resistance in the simulated cathodic environment of PEMFC.