Decrease In Corrosion Resistance Research Articles

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.

The effect of silica NPs incorporation on protective properties of oxide layers formed by PEO on Mg97Y2Zn1 alloy with LPSO-phase

The inherited chemical inhomogeneity in oxide layers obtained by plasma electrolytic oxidation (PEO) on the magnesium alloy Mg97Y2Zn1 is associated to long-period stacking-ordered (LPSO) phase present in the treated alloy. This heterogeneity results in decrease of corrosion resistance and adhesion strength. The problem was solved by adding silica nanoparticles (NPs) into the electrolyte under PEO. According to the model developed, NPs which are harder than the oxide layer and being electrically charged, can be accelerated by an electric field and penetrate deep into the layer. The near-surface incorporation of NPs results in branching of the local breakdowns of vapor-gas bubbles that leads to an increase of the volumes of oxide layer and improvement of its properties.

Study on the effect of magnetic field on electrodeposition of NiCr alloy coating

Different NiCr coatings are prepared by magnetic field assisted electrodeposition on the surface of Q235B substrate. The influence of magnetic field intensity on thickness, surface roughness, hardness, surface morphology, composition, and corrosion resistance of NiCr coating is studied. The Lorentz force generated by the interaction of magnetic field and electric field will produce magnetohydrodynamic (MHD) phenomena near cathode surface to improve ions transfer rate and reduce the surface roughness, resulting in the increase of thickness and hardness. The electrodeposited NiCr coatings all show granular surface morphology. The metal cellular protrusions on the surface of NiCr coating prepared without magnetic field are nonuniform and agglomerated. The applied magnetic field is beneficial to refine the metal cellular protrusions and increase the chromium content in the NiCr coating, resulting in the enhancement of corrosion resistance. The NiCr coating obtained at the condition of 1T magnetic field has the largest thickness and the best corrosion resistance. However, when the magnetic field is increased to 1.5T, the chromium content in CoNi coating is reduced due to severe hydrogen evolution, resulting in the decrease of hardness and corrosion resistance.

Effect of laser energy densities on the phase composition change in laser-cladded AlCoCrNbMo high-entropy alloy coatings

This work designed a new high-entropy alloy (HEA), namely, AlCoCrNbMo, and prepared it by using laser cladding (LC). The effects of different values of laser energy density (Es) on the phase composition, microstructure, mechanical properties and corrosion resistance of the HEA coating were investigated via X-ray diffractometry; scanning electron microscopy; energy dispersive spectrometry and microhardness, friction wear and electrochemical tests. Results indicate that increasing Es (Es = 35, 55, 75 J/mm2) leads to the formation of different phases, including bcc1, bcc1 +bcc2 and bcc1 +bcc2 +Al3Nb, in the coating. The bcc1 phase is rich in Co and Cr elements, whereas the bcc2 phase is rich in Nb and Mo elements. As Es increases, the HEA coating shows increasing hardness and wear resistance but decreasing corrosion resistance. Moreover, the AlCoCrNbMo alloy prepared through vacuum arc melting does not conform to the form of HEAs but is instead composed of various intermetallic compounds, reflecting the unique advantage of LC. This paper discusses the influence of LC process parameters on the microstructure of HEAs and the unique advantages of LC for HEA preparation.

Study on the microstructure and corrosion resistance of Zn-3Al-xMg alloy

Low-aluminium Zn-Al-Mg alloys (Al content is 1–3 %) were expected to be widely used in automotive panels due to their good coating properties and surface quality. However, the effect of Mg on the microstructure and corrosion resistance of Zn-Al-Mg alloys has not been studied thoroughly enough. In order to investigate the corrosion resistance law of Mg on Zn3Al alloys. The microstructure and corrosion resistance of Zn-3Al-xMg (x = 0.5, 1, 2, 3 wt%) alloys were investigated in the present work. The ternary eutectic (Zn/Al/MgZn2) in the microstructure increased, and the Al-rich phase disappeared with increasing Mg. The grains were also refined. The maximum ratio of ternary eutectic in the alloy was achieved by controlling the Mg content, contributing to the most favourable corrosion resistance. The electrochemical and corrosion behaviour analysis indicated that the Zn-3Al-2Mg alloy exhibited superior corrosion resistance due to the lower presence of Al-rich phases and a larger ternary eutectic area. However, the ternary eutectic in the alloy was completely transformed into Zn/Al/Mg2Zn11 when the Mg was 3 %, leading to decreased corrosion resistance. The corrosion resistance mechanisms of Zn-3Al-xMg were analyzed and discussed by studying the microstructure changes, electrochemical analysis, corrosion morphology, and products of the Zn-3Al-xMg alloy.

Temperature induced cathode-anode reversal behavior of TA2–304 L galvanic couple in simulated spent fuel reprocessing media

Galvanic corrosion is prevalent throughout various stages of spent fuel reprocessing, and plays a crucial role in the corrosion failure of equipment materials due to its pronounced local corrosive effects. Nevertheless, there is a scarcity of systematic investigations regarding the impact of temperature on the corrosion mechanism of galvanic couples in simulated spent fuel reprocessing media. This study aims to explore the electrochemical behavior and passive film characteristics of TA2–304 L galvanic couple immersed in nitric acid solutions at different temperatures. Relevant results indicated that temperature significantly affected the galvanic corrosion behavior of TA2–304 L couple in nitric acid. The galvanic couple demonstrated a notable reversal in cathodic and anodic polarity with the rising temperature, which was closely related to the changed corrosion mechanism of 304 L SS from superior passivation performance to severe intergranular corrosion. Meanwhile, a critical temperature phenomenon was observed for TA2, below which there exhibited a monotonically decreased corrosion resistance with the increase in temperature. However, an improved corrosion resistance was found as the temperature rose to 120 °C, which could be associated with the decreased oxidative properties of nitric acid because of the variation in electrochemical/chemical reactions. Additionally, the relationship between corrosion rate and temperature of both 304 L SS and TA2 was created, and the activation energy was calculated to stress the influence of temperature on the corrosion of both materials. Eventually, the galvanic mechanism of TA2–304 L couple with temperature in nitric acid was proposed.

In situ observation of electrochemical reaction of Zn primer steel plate in NaCl solution using confocal micro‐x‐ray fluorescence imaging

AbstractSteel plates have been widely used in bridges, vehicle bodies, guardrails, and so forth. Generally, to improve corrosion resistance, the surface of a steel plate is coated with a Zn layer. However, when the coated steel plate is scratched by external factors, the corrosion resistance decreases. Therefore, it is important to elucidate the elution processes of elements in coated layers and steel plates to develop new coated films and improve corrosion‐resistant techniques. During corrosion, an elution reaction between the coated metal and Fe (anodic reaction) and a reduction reaction of oxygen (cathodic reaction) occur. Confocal micro‐x‐ray fluorescence imaging was employed to visualize the elution processes at the anodic and cathodic steel plates. A Zn primer steel plate was scratched and then immersed in sodium chloride solution. The Zn elution process at the anodic side was observed when a constant current was applied to the two steel plates by a galvanostat. The Fe elution process did not occur, and we believe that the sacrificial protection of Zn inhibited the process. The elutions of Zn and Fe were not observed on the cathodic side of the steel plate. Using the proposed method, we successfully visualized the elemental distributions at the anodic and cathodic sides of the steel plates.

Microstructure evolution and corrosion behaviors of cold-rolled 304 stainless sheets of steel in 3.5% NaCl solution

Austenitic stainless steel (ASS) is widely used in engineering applications due to its good corrosion resistance and mechanical properties. Several studies have indicated that the deformation-induced transformation of martensite in ASS significantly affects its corrosion resistance. However, corrosion resistance behavior in chloride-rich environments is more complex, and different cold-working methods have distinct impacts on localized corrosion. This study investigated the structural and corrosion resistance changes induced by cold rolling in AISI 304 samples. The used samples were initially subjected to a cold-rolling process with a thickness reduction of up to 50%. The results demonstrate an increase in the deformation-induced martensitic transformation and micro-hardness as the level of cold deformation increases. However, higher levels of deformation lead to the fragmentation of the formed a’‑martensite lath structure into smaller laths, ultimately resulting in a predominantly refined and diffuse dislocation-cell-type structure. Potentiodynamic tests were conducted to analyze conventional electrochemical parameters, revealing a reduction in corrosion resistance with increasing cold deformation. This suggests that the formation, amount, and microstructure of a’‑martensite, under imposed strain conditions, induce changes in the studied electrochemical parameters. Additionally, the more deformed samples exhibited a higher current density during passive layer formation, and exhibited more intense metastable pits, suggesting decreased corrosion resistance with higher degrees of deformation.

Microstructure and surface performance of hydroxyapatite-modified multilayer amorphous coating on Ti-rich TiNbZrSn medium entropy alloy: A comparative study

The present study focuses on the formation of a hydroxyapatite-modified amorphous micro-arc oxidized (MAO) coating on the TiNbZrSn medium entropy alloy (TNZS MEA) through micro-arc oxidation and microwave hydrothermal treatment (MHT). The TNZS MEA primarily consists of a body-centered cubic (bcc) and hexagonal closed-packed (hcp) structure, exhibiting a low elastic modulus and high yield strength. A porous coating with an amorphous structure was obtained after MAO treatment, displaying superior corrosion resistance to MAOed Ti. After MHT, the MAOed TNZS MEA exhibited a multilayered structure consisting of three layers: an external growth layer (hydroxyapatite nanorods), an inner layer (amorphous and crystalline structures), and a substrate layer. This composite structure demonstrated enhanced superior apatite-inducing ability and corrosion resistance compared to MHTed Ti. The improvement in bioactivity and a slight decrease in corrosion resistance can be attributed to the incomplete structure of hydroxyapatite nanorods when compared to MHTed Ti. Consequently, this work successfully achieved a hydroxyapatite-modified multilayered oxidized coating with gradient performance in term of bioactivity and corrosion resistance, establishing it as a promising candidate material for hard tissue repair.

Effect of UV Irradiation on the Alternating Wet and Dry Corrosion Behavior of Galvanized Steel in Sodium Chloride Solution

In this paper, the corrosion performance of galvanized steel was investigated in a simulated marine environment, under UV irradiation coupling with an alternating wet and dry cycle in a NaCl solution. The surface morphology, composition, and corrosion performance of galvanized steel before and after different alternating wet and dry corrosion under UV irradiation were investigated. The results show that the corrosion current density gradually increases and the corrosion resistance decreases as a function of the alternating wet and dry corrosion cycles. Meanwhile, UV irradiation accelerates the increase in the corrosion current density and the decrease in the corrosion resistance. In addition, the corrosion product ZnO shows a semiconductor property, and the photo-induced electrons and holes produced under UV can participate in the corrosion reaction and promote the formation of loose corrosion products Zn(OH)2, Zn5(OH)8Cl2, and Al2Cl3(OH)5·4H2O, thus accelerating the corrosion of galvanized steel in the atmosphere environment.

β-TCP particles additive synergistically improves corrosion resistance and biocompatibility of micro-arc oxide coated magnesium alloy

Optimizing micro-arc oxidation (MAO) coating by introducing functional particles has attracted increasing attention in fields about surface modification of magnesium alloys. However, the incorporation of particles usually destroys the integrity of the coating and resulting in the decreased corrosion resistance. In this work, β-tricalcium phosphate (β-TCP), a degradable calcium phosphate, was introduced in the MAO coating on magnesium surface. The results show that the introduction of β-TCP simultaneously enhances the long-term corrosion resistance and biocompatibility of MAO coating. This work provides a strategy to synergistically improve the corrosion resistance and biocompatibility of magnesium alloy for orthopedic applications.

Effect of silicon addition on the corrosion resistance of Al0.2CoCrFe1.5Ni high-entropy alloy in saline solution

In the paper, the effect of Si content on the microstructure evolution and corrosion properties of Al0.2CoCrFe1.5NiSix (x = 0, 0.1, 0.2, 0.3) high entropy alloys (HEAs) was systematically investigated. With the addition of Si element, the microstructure changed from single face-centered cubic (FCC) phase in the Al0.2CoCrFe1.5Ni and Al0.2CoCrFe1.5NiSi0.1 HEAs to a dual-phase structure composed of FCC and body-centered cubic (BCC) phases in the Al0.2CoCrFe1.5NiSi0.2 and Al0.2CoCrFe1.5NiSi0.3 HEAs. In addition, the corrosion mechanism has been analyzed by elemental analysis and corrosion morphology. The electrochemical measurement results indicated that the Al0.2CoCrFe1.5NiSi0.1 HEA possessed the best corrosion resistance (Ecorr = − 215 mVAg/AgCl, Icorr = 256 nA/cm2) because the small amount of Si element improves the corrosion resistance of the single-phase FCC HEA. When the Si content increased to 4.08 at% (x = 0.2) and 6.00 at% (x = 0.3), the galvanic corrosion was caused by BCC, resulting in the selective dissolution of the BCC phase and the decrease of corrosion resistance. This research results will help to understand the potential applications of doped trace Si element as a matrix element in single-phase FCC HEAs with good corrosion resistance.

Evaluation of the Mechanical and Corrosion Behavior of Twin Wire Arc Sprayed Ni-Al Coatings with Different Al and Mo Content

In this study, the surface properties of marine structures were improved by applying a twin wire arc spray process to high-strength low alloys. The effect of Al and Mo contents in Ni-Al coatings on their mechanical and corrosion behaviors was analyzed using hardness tests, electrochemical experiments, and immersion tests. The increase in Al content resulted in the formation of oxides and intermetallic compounds, leading to a significant improvement in the mechanical properties by approximately 222 HV. Despite a fine galvanic phenomenon causing a decrease in corrosion resistance by up to 8.91%, a higher Al content demonstrated the highest corrosion resistance after high-temperature exposure, with an enhancement of approximately 20.9%, attributed to the formation of an oxide film generated by intermetallic phase transformation. However, the mechanical properties experienced a reduction of 134.3 HV. This study demonstrated a correlation between the microstructure of the coating layers that form passivation films and their respective mechanical and corrosion properties. It also revealed that the content of Al and Mo significantly affects the mechanical and corrosion behavior of Ni-Al coatings.

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.