Decrease In Corrosion Resistance Research Articles

Effect of Si and Nb additions on carbonitride coatings under proton irradiation: A comprehensive analysis of structural, mechanical, corrosion, and neutron activation properties

In the present study, understoichiometric TiZrCN, TiZrNbCN, and TiZrSiCN coatings were produced using the cathodic arc technique with a C/N ratio of approximately 0.5 to investigate their potential use in nuclear technology. The coatings were evaluated for their corrosion resistance in 3.5 % NaCl and neutron activation. The effect of adding Si and Nb to the quaternary TiZrCN system was also investigated. The results showed that the addition of Si (∼4.64 at.%) to the matrix of TiZrCN improved their electrochemical properties in NaCl solution, the protective efficiency was 92%, while the Nb addition (∼5.5 at%) lead to the decrease in corrosion resistance by 1.39 times comparing with TiZrCN. Furthermore, after fast neutron irradiation at a nominal power of 1450 kW, none of the coatings were activated, indicating good radiation resistance. It was determined from the structural analysis that the Ti6Al4V substrate before corrosion consists of hexagonal and cubic space groups with different lattice parameters. By adding Si and Nb, a small amount of ZrO2 and Si3N4 was detected along with the main phases in the TiZrCN structure.

An efficient strategy for enhancing the corrosion resistance of S31254 super austenitic stainless steel through slight Mo segregation

Super austenitic stainless steel (SASS) is one kind of high Mo-alloy steel with excellent corrosion resistance when applied in an extremely corrosive environment. However, high contents of Cr and Mo tend to form precipitates along the grain boundary at high temperatures, leading to a great deterioration of corrosion resistance. Herein, a method of short-time aging treatment at 500 °C and 550 °C was explored, which was intended to regulate the distribution of elements at grain boundaries to improve corrosion resistance. The results indicate that before the precipitates nucleation, as the temperature rises from 500 °C to 550 °C, the Mo element has obvious diffusion behavior towards the grain boundary. Also, the uniform distribution of a small amount of Mo at the grain boundary can be conducive to improving the corrosion resistance. In addition, B inhibits the separation of Mo to grain boundary and delays the formation of the precipitated phase. The addition of B improves the intergranular corrosion resistance of SASS, especially after aging at 500 °C, which is attributed to the passivated film's Cr2O3 and Mo(VI) content. However, when the aging temperature reaches 550 °C, more Mo segregates to the grain boundaries, resulting in Mo-depleted zones, which decreases corrosion resistance.

Effect of heat input on microstructure and corrosion resistance of high-nitrogen austenitic stainless steel welded joints

In this study, the microstructure and corrosion resistance of high-nitrogen austenitic stainless steel welded joints with different heat inputs were investigated. A high heat input leads to a large width and depth of the fusion pool and a low fraction of δ-ferrite in the weld sea. However, a high fraction of Cr-rich precipitates is formed under a high heat input and low heat promotes the formation of δ-ferrite. Therefore, following corrosion tests, the weld seam suffers severe intergranular corrosion under high heat input and low heat input, and the corrosion resistance of the weld is the highest at a heat input of 6.8 kJ/cm. A high heat input results in a high fraction of Cr-rich precipitates and a random boundary in the heat affected zone (HAZ), which decreases corrosion resistance. Furthermore, corrosion test results indicate that the Cr-depleted area and random boundary are initially corroded, and high heat input decreases corrosion resistance of the HAZ.

Cavitation erosion-corrosion behaviour of Fe-19Cr-15Mn-0.66 N high nitrogen austenitic stainless steel in sodium chloride solution

In this work, the cavitation erosion (CE)-corrosion behaviors of high nitrogen austenitic stainless steel (HNSS) Fe-19Cr-15Mn-0.66 N were investigated under both static and CE conditions in 0.5 mol l−1 NaCl solution. For the sample after 8 h CE, the cumulative mass loss increased by 15% in 0.5 mol l−1 NaCl solution compared to distilled water, indicating that the corrosive media promoted mass loss. The corrosion behavior of the samples under static and CE conditions was evaluated using electrochemical techniques. The results showed that compared with the samples under static conditions, the samples under CE had a higher corrosion rate, and the corrosion resistance of the samples gradually decreased with the prolongation of C E time.The open circuit potential and potentiodynamic polarization tests showed a higher corrosion rate under CE conditions. The electrochemical impedance spectroscopy results revealed a decrease in corrosion resistance with increasing CE time. The XPS results showed that CE has a significant effect on the composition of the passive film, promoting a notable increase in Cr2O3 and Fe2O3.

Tailoring the strength and corrosion resistance of Al-7Si: Eutectic Si modification by Sr and Sc

The effects of different content of Sr and Sc on the microstructure, mechanical properties and corrosion resistance of an Al-7Si alloy were investigated. The presence of Sc in the Sr-modified Al-Si alloy resulted in multiple types of eutectic Si morphologies. The modification of eutectic Si improved the yield strengthen and elongation of Al-7Si alloys, but lead to the increase of boundaries between α-Al and eutectic Si particles, which caused decrease of corrosion resistance and polarization resistance. The incomplete modification offered a possibility to satisfy the require that a compromise between mechanical properties and corrosion resistance. The relationship between the content of Sr and Sc and the morphologies of eutectic Si in the alloy was also summarized.

Microstructural evolution of superaustenitic stainless steel weld metal subjected to post welding heat treatment

Superaustenitic stainless steels are widely applied in the industry as alternatives to cheaper stainless steels or nickel alloys due to their combination of strength, weldability, and good corrosion resistance. However, the literature addressing the behavior of superaustenitic stainless steel weld metals is scarce and sometimes the lack of knowledge limits their use in claddings or dissimilar welding. Although some few works have shown promising results of weld metals in the as welded condition, no reports showing the effect of post welding heat treatment on the microstructure and properties of GMAW weld metals are available. This work shows that the austenitic microstructure with a low volume fraction of χ-phase of weld metals deposited by the GMAW process changes dramatically after post weld heat treatment. The precipitation of the σ-phase forming a network of small particles along the grain boundaries for temperatures higher than 800 0C promotes a significant detrimental effect on the corrosion properties, even for a low fraction of secondary phases. It is concluded that the σ-phase decorating the grain boundaries is the main contributing factor to the decrease of corrosion resistance, regardless of the fraction of secondary phases.

Laser Powder Bed Fusion of 316L Stainless Steel: Effect of Laser Polishing on the Surface Morphology and Corrosion Behavior

Recently, laser polishing, as an effective post-treatment technology for metal parts fabricated by laser powder bed fusion (LPBF), has received much attention. In this paper, LPBF-ed 316L stainless steel samples were polished by three different types of lasers. The effect of laser pulse width on surface morphology and corrosion resistance was investigated. The experimental results show that, compared to the nanosecond (NS) and femtosecond (FS) lasers, the surface material’s sufficient remelting realized by the continuous wave (CW) laser results in a significant improvement in roughness. The surface hardness is increased and the corrosion resistance is the best. The microcracks on the NS laser-polished surface lead to a decrease in the microhardness and corrosion resistance. The FS laser does not significantly improve surface roughness. The ultrafast laser-induced micro-nanostructures increase the contact area of the electrochemical reaction, resulting in a decrease in corrosion resistance.

Advancement of Novel Graphene Oxide Embedded Alumina Nickel Composite Coating Developed at Various Current Densities to Evaluate Corrosion Resistance

In this research, the influence of deposition current density on the properties of nickel-Graphene oxide/alumina coatings produced by electrodeposition was examined. Nickel matrix composite coatings with graphene oxide doped Alumina (GO-Al2O3) particles were prepared via electrodeposition. When embedding GO-Al2O3 particles in the Ni matrix, remarkable anti-corrosion properties are anticipated due to the outstanding mechanical properties of GO and Al2O3. The structure, content, and morphology of GO, GO-Al2O3, and coatings deposited at various current densities were determined using X-ray diffraction, Fourier transforms infrared spectroscopy, Field emission Scanning electron microscopy, and energy-dispersive X-ray spectroscopy. GO-doped alumina particles were successfully incorporated into the matrix of nickel, according to the findings. Porosity measurement and cross-sectional thickness were also investigated at various current densities. Potentiodynamic polarization testing and electrochemical impedance spectroscopy were used to study the coatings' corrosion-resistant characteristics. According to the findings, coatings developed at high current densities, such as 30 mA cm-2, are porous and not uniform in nature. Furthermore, at high current densities, the content of GO and Alumina is reduced, resulting in a decrease in mechanical and corrosion resistance. Due to its less porous and uniformly formed coating, 10 mA cm-2 was the optimum current density for achieving the most desirable features.

Improved corrosion resistance of 2195 Al-Cu-Li alloy through T6I6 interrupted aging

An interrupted aging treatment, T6I6, was conducted on 2195 Al-Cu-Li alloy to improve the corrosion resistance. The microstructure evolution, intergranular corrosion (IGC), exfoliation corrosion (EXCO), and electrochemical corrosion behaviors of 2195 Al-Cu-Li alloy subjected to T6I6 and T6 aging treatment were systematically investigated. The results reveal that the number density of T1 (Al2CuLi) phases in the grain interior and at the grain boundaries of T6I6 sample increases by suppressing the precipitation of θ' (Al2Cu) phases. The higher density of T1 phases along the grain boundary can increase the potential difference between the grain boundary precipitates (GBPs) and Al matrix, resulting in decreased corrosion resistance. However, the GBPs coarsening and precipitate free zone (PFZ) narrowing induced by interrupted aging offset the harmful effects of T1 phases, which are responsible for the improved corrosion resistance of T6I6 sample. Hence, the proposed T6I6 aging treatment more effectively improves the corrosion resistance for the studied alloy compared to T6 aging.

Effect of SiO2 nanoparticles on the hardness and corrosion resistance of NiW/SiO2 nano composite coating prepared by electrodeposition

In this paper, NiW/SiO2 composite coatings were prepared on Q235B steel using the electrodeposition technique. The relationship between the concentration of SiO2 nanoparticles in the plating solution and the properties of NiW/SiO2 composite coating was investigated. The results show that the addition of an appropriate amount of SiO2 nanoparticles in the plating solution can enhance the cathode current, increase the surface hardness, improve the corrosion resistance, and reduce the roughness of the composite coating. The SiO2 nanoparticles covered on the coating surface can penetrate the lattice of NiW alloy to induce heterogeneous nucleation, and play a role in refining grain. However, when the SiO2 nanoparticles in the plating solution reaches 8 g/L, the agglomeration phenomenon occurs due to excessive nanoparticles, which will increase the roughness and decrease the compactness, resulting in the decrease of hardness and corrosion resistance. The NiW/SiO2 composite coating electrodeposited from the solution containing 6 g/L SiO2 nanoparticles exhibits the best hardness (643.23 HV) and the greatest corrosion resistance with the smallest corrosion current density (9.7 μA/cm2).

Corrosion and corrosive wear of AlCrFeCoNi and Co-free AlCrFeNi-Tix (x = 0–1.5) high-entropy alloys in 3.5 wt % NaCl and H2SO4 (pH = 3) solutions

The Co-free AlCrFeNi HEA has good application prospects for its simple duplex BCC phase structure and attractive mechanical properties. In this work, influences of Ti on corrosion and corrosive wear of AlCrFeNi alloy in salty and acidic solutions were investigated and compared with those of AlCrFeCoNi. Results showed that removing Co led to little influence on hardness but only a slight decrease in corrosion resistance. However, the corrosive wear resistance was significantly improved, which was attributed to improved ductility, which benefited the toughness, of the Co-free AlCrFeNi alloy. AlCrFeNiTi0.5 showed the lowest passivation current and its corrosion current density was only about one-third that of SS316. A strong correlation was found among the corrosive wear resistance, corrosion resistance, hardness and brittleness. Titanium can improve the anti-corrosive wear ability of AlCrFeNi alloy with increased hardness, higher corrosion resistance, and enhanced protectiveness of formed surface oxide film. However, as the Ti content exceeded a certain level, corrosive wear of Ti-containing alloys was accelerated by easy formation of crack and delamination in substrate which led to a negative effect on the corrosive wear resistance, although the alloys showed higher hardness.

Effect of heat treatment atmospheres on microstructure evolution and corrosion resistance of 2205 duplex stainless steel weldments

The effects of post heat treatment atmosphere on microstructure and corrosion resistance of duplex stainless steel welded joints were investigated. Post weld heat treatment (PWHT) was carried out with and without protective atmospheres. Nitrogen and argon are used as protective gases individually. Detailed microstructure examination (optical and SEM) demonstrates that nitrides precipitates are highly observed in the welded zones for nitrogen protected samples. An observed drop of ferrite volume fraction in post weld heat treated samples compared with welded samples without heat treatment leading to corrosion resistance enhancement of heat treated welded joints. An exception for using nitrogen as heat treatment atmosphere a decreased corrosion resistance of weldments is investigated due to nitride precipitates. An increase in the weld zone hardness for post weld heat treated samples compared with base alloy. The initial hardness of duplex stainless steel was 286 Hv while average hardness of weld zone was 340, 411, 343, and 391 Hv for as welded, PWHT using air, argon, and nitrogen atmospheres, respectively. Weld zone hardness increased to 33, 44, 20, and 37%. A significant decrease in the ultimate tensile strength and elongation after PWHT. The initial Ultimate tensile strength duplex stainless steel base material was 734.9 MPa while Ultimate tensile strength of the welded joints was 769.3, 628.4, 737.8, and 681.4 MPa for the following conditions: as welded, PWHT using air, argon, and nitrogen atmospheres, respectively.

Alloy design for microstructural-tailored boron-modified ferritic stainless steel to ensure corrosion and wear resistance

Ferritic stainless steels armored with borides had their endurance tested in demanding both abrasive and corrosive environment. The degradation was investigated through a very aggressive plate-on-cylinder wear test in water-based drilling mud containing chlorides, which was designed to simulate, in laboratorial scale, the corrosive tribosystem found in the wear of risers and casings used in deep water oil exploitation. A commercially-grade 430 ferritic stainless steel containing boron content far beyond its solubility limity, namely 1.2 and 3.5 wt.%, was processed by spray-forming to induce a ferritic stainless steel matrix protected by a boride skeleton. Additional corrosion assessment was performed by potentiodynamic polarization and electrochemical impedance spectroscopy in 0.27 M KCl solution, since KCl is a common clay swelling inhibitor. For comparison, API 5L X80 steel was also included since this material is used in risers and casings manufacture. The addition of boron (1.2 and 3.5 wt.%) led to the formation of microstructures composed of an α-ferrite matrix with homogeneously distributed M2B-type borides of different morphologies. Electrochemical tests revealed high corrosion resistance of the alloy with 1.2 wt.% B. However, the alloy with 3.5 wt.% B showed a considerable decrease in corrosion resistance due to Cr-depletion of the ferritic matrix given the M2B formation richer in Cr. Therefore, the alloy with 1.2 wt.% B offered the best tribocorrosion resistance.

Mechanical and Corrosion Behavior of Zr-Doped High-Entropy Alloy from CoCrFeMoNi System.

The aim of the paper is to study the Zr addition effect on the mechanical properties and corrosion behavior of a high-entropy alloy from the CoCrFeMoNi system. This alloy was designed to be used for components in the geothermal industry that are exposed to high temperature and corrosion. Two alloys, one Zr-free (named Sample 1) and another one doped with 0.71 wt.% Zr (named Sample 2), were obtained in a vacuum arc remelting equipment from high-purity granular raw materials. Microstructural characterization and quantitative analysis by SEM and EDS were performed. The Young modulus values for the experimental alloys were calculated on the basis of a three-point bending test. Corrosion behavior was estimated by linear polarization test and by electrochemical impedance spectroscopy. The addition of Zr resulted in a decrease in the value of the Young modulus but also in a decrease in corrosion resistance. The beneficial effect of Zr on the microstructure was the grain refinement, and this ensured a good deoxidation of the alloy.

Laser surface alloying of titanium alloy with silver: Microstructure, hardness and corrosion property

In this study, silver (Ag) was surface-alloyed in TC4 alloy (Ti6Al4V) with a high-power diode laser (HPDL). The Ag content in the alloyed layers were controlled to be 5 to 24 wt%. The microstructure, hardness and corrosion properties of the alloyed layers are affected by the Ag content. The hardness of TC4 alloy, when laser surface-alloyed with 14 wt% Ag increased from 381 HV0.2 to a maximum value of 569 HV0.2, caused by the formation of hard intermetallic phases (Ti2Ag and TiAg) in the α-Ti matrix. However, with the increase of Ag content to 24 wt% the hardness of the alloy was lowered to 456 HV0.2, result of the formation of a soft Ag-rich phase. In addition, observing a decrease in corrosion resistance of the laser surface-alloyed TC4 with a high Ag content, which is attributed to micro-galvanic effect between the α-Ti and Ti2Ag, TiAg and Ag-rich phase.

Role of Grain Size and Recrystallization Texture in the Corrosion Behavior of Pure Iron in Acidic Medium

This work investigates the role of grain size and recrystallization texture in the corrosion behavior of pure iron in 0.1 M sulfuric acid solution. Annealing heat treatment was applied to obtain samples with different average grain sizes (26, 53 and 87 µm). Optical microscopy, X-ray diffraction and electron backscatter diffraction techniques were used to characterize the microstructure. The EBSD data analysis showed ferrite phase with no inclusions and very low geometrically necessary dislocation density, indicating strain-free grains constituting all samples. The crystallographic texture analysis of the samples revealed that the 26 µm grain size sample had a high volume fraction of {111} oriented grains parallel to the sample surface, while other samples exhibited nearly random crystallographic texture. The electrochemical results from potentiodynamic polarization and electrochemical impedance spectroscopy showed a decrease in corrosion resistance from 87 µm to 53 µm grain size sample and then an increase for the 26 µm grain size sample. This increase was attributed to the dominant effect of recrystallization texture on the corrosion behavior of the sample. The cathodic hydrogen evolution reaction kinetics was found to play a decisive role in the corrosion behavior of iron.

The Influence of Different Type Materials of Grit Blasting on the Corrosion Resistance of S235JR Carbon Steel

The aim of this paper is to evaluate the corrosion rate expressed in material loss per unit of time and the surface properties of carbon steel type S235JR blasted with different types of materials (quartz, alumina, and red garnet with a particle size between 60 and 80 mesh (0.25–0.60 mm)). The estimation of corrosion rate was determined by electrochemical methods, such as open circuit potential (OCP), polarization resistance (Rp), corrosion rate (Vcorr), and gravimetric method by immersing the samples in 3.5% NaCl solution for a period of 336 h. All surfaces were characterized before and after corrosion tests using ex-situ characterizations, such as optical microscopy and roughness analysis. The results indicate that S235JR non-sandblasted exhibited higher polarization resistance, the lowest corrosion rate, and the lowest roughness values. While for the S235JR sandblasted groups, reduced corrosion resistance and increasing roughness values were noted. From the sandblasted groups, the lowest corrosion resistance and the highest value of roughness are attributed to the S235JR surface sandblasted with quartz. The S235JR surface sandblasted with quartz shows a decrease in corrosion resistance approximately two times lower than the non-sandblasted surface and an increasing of roughness approximately six times greater than the non-sandblasted surface.

Properties of sodium molybdate-based compound corrosion inhibitor for hot-dip galvanized steel in marine environment

Abstract Sodium molybdate (Na2MoO4) was selected as the corrosion inhibitor, compounded with benzimidazole, in order to prolong the service life of the hot-dip galvanized steel (HDGS) in the marine environment in this article. XRD, SEM/FESEM and EDS were used to characterize the micro-morphology and elemental composition of HDGS. Immersion corrosion test, Tafel polarization and EIS test were carried out to study the effect of compound inhibitor on the corrosion resistance of HDGS in the marine environment. The best proportion of compound inhibitor was added to the self-made waterborne polyurethane coating (WPUC), aiming to evaluate its influence on the coating performance in the marine environment by immersion corrosion test and EIS test. The results showed that Na2MoO4, as a passivation type corrosion inhibitor, bounded Zn at the active sites of HDGS coupons and created structural defects. Benzimidazole, as an adsorption type corrosion inhibitor, was attracted by electricity and adsorbed at the structural defects. Under the premise of 1 wt% total content, the optimal ratio of Na2MoO4 & benzimidazole was 9:1 and the corrosion inhibition efficiency was 99.62%. The corrosion current density of HDGS in the simulated seawater with compound inhibitor was 5.650 × 10−8 A/cm2, while that of HDGS in the simulated seawater without compound inhibitor was 1.483 × 10−5 A/cm2. The WPUC containing compound inhibitor had a small decrease in corrosion resistance due to defects created by doping at the beginning of immersion, then the compound inhibitor would play an active role in the corrosion process to make more than double the service life of WPUC.

Characterization of cryo-rolled low carbon steel using ferrite-martensite starting microstructure

Cryo-rolling, a technique of severe plastic deformation (SPD) performed at cryogenic temperatures, has proven to be a promising technique for improving the microstructure and mechanical properties of low-carbon steels. Low carbon steel with a two-phase ferrite-martensite starting microstructure was subjected to cryogenic rolling at liquid nitrogen temperature to produce sheets with different deformation rates: 50%, 70%, and 90%. The microstructure, mechanical properties, and corrosion resistance were investigated. The results show that cryo-rolling effectively refines the microstructure and leads to a higher dislocation density and smaller grain size as the deformation rate increases. The cryorolled sample deformed at 90% has the highest grain aspect ratio (35.5), the smallest crystallite size (13.70 nm), the highest lattice strain (74.6 x 10-3), and the highest dislocation density compared to the samples deformed at 50% and 70%. This refined microstructure significantly improves the mechanical properties, with the cryo-rolled sample deformed at 90% exhibiting the highest hardness (152 HV), tensile strength (1020 MPa), and yield strength (950 MPa), corresponding to an increase of 175.6%, 344.0%, and 466.5%, respectively. In addition, cryo-rolling at 90% showed a decrease in corrosion resistance, with the lowest corrosion rate observed at 90% deformation (5.97 mm/year).

Corrosion resistant degradation of AISI 304 austenitic stainless steel exposed to simulated carburizing environments

This paper aimed to evaluate the anti-corrosion performance of AISI 304 austenitic stainless steel after exposure to the simulated carburizing environment set up at 600oC, 750oC, and 900oC for 4 hrs. The microstructural alternation was investigated by Scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). Electrochemical Potentiokinetic Reactivation (EPR) was employed to study the anti-corrosion performance of AISI 304 austenitic stainless steel after exposure to the simulated carburizing environment. Hardness measurement was also conducted to study the role of carbon atoms released from the simulated environment. The results showed the formation of precipitated chromium carbides along grain boundaries and sensitization degree was found in ascending order: 600oC (Pa =0.23), 750oC (Pa =0.32) and finally 900oC (Pa =0.41). All carburized conditions promote carbon dissociation and diffusion through the substrate of AISI 304 austenitic stainless steel, resulting in the increased hardness and decreased corrosion resistance of AISI 304 austenitic stainless steel after exposure to the simulated carburizing environment.