Difference In Corrosion Behavior Research Articles

Microstructure and Corrosion Behavior of Ti-Mo-Zr Alloy Fabricated by Selective Laser Melting in Simulated Oral Environment

The microstructure of Ti-Mo-Zr alloy fabricated by selective laser melting (SLM) was studied and its corrosion behavior was investigated by a series of electrochemical methods. The results showed that α+β phases of different proportions were formed after heat treatment, the grain size of the alloy treated at 950℃ slightly increased, because of the existence of the original α grain, the orientation of the α grain was not significantly changed by heat treatment below the β transition temperature. However, heat treatment above β transition temperature significantly changed the orientation of α grains. Electrochemical measurements were conducted in artificial saliva solution and artificial saliva solution containing hydrogen peroxide. The results showed that the corrosion resistance of the original Ti-Mo-Zr alloy was better than that of the Ti-Mo-Zr alloy treated at 950°C and worse than that of the Ti-Mo-Zr alloy treated at 1050°C. The differences in corrosion behavior can be attributed to grain size and orientation and phase distribution.

Study on Initial Corrosion Behavior of Arc-thermally Spray Zn, Zn–Al, and Al–Mg Coatings Exposed in Atmospheric Environment for One-Year

AbstractThis paper presents the results of a study comparing the initial corrosion characteristics of thermal spray coatings on Zn, Zn-Al, and Al–Mg thermal spray coatings after one year atmospheric exposure tests at two atmospheric environment sites. The thermal spray coatings were obtained by electroric arc spraying of various metals onto a carbon steel substrate. Atmospheric exposure tests were also conducted for outdoor accelerated exposure tests in which test specimens were applied with artificial seawater. The corrosion properties of these spray coatings were evaluated by surface analysis, film thickness measurements, cross-sectional analysis and anodic/cathodic polarization measurement. After one year of atmospheric exposure testing, white, granular corrosion products were observed on the surface of the Zn and Zn-Al thermal spray coatings, while no significant changes were observed in the Al–Mg thermal spray coating. Similar results were obtained for the surfaces of test specimens in atmospheric exposure tests with artificial seawater. The thickness of the thermal spray coating increased for the Zn thermal spray coating, while no significant change was observed for the other thermal spray coatings. Thus, differences in corrosion behavior were observed due to the composition of the thermal spray coatings. The initial corrosion behavior of the thermal spray coatings was also investigated based on the results of coating morphology and cross-sectional elemental distribution of the coatings.

Effect of Non-Essential Alloying Elements and Solution pH on Corrosion Behavior of Al-Mg Alloys Fabricated by Cold Spray Deposition

ABSTRACT This paper highlights the difference in corrosion behavior of cold spray (CS) deposited AA5083 and Al-5.0 wt.% Mg alloys with an emphasis on the effect of non-essential alloying elements and solution pH. CS process is an emerging technology to repair damaged structures via solid-state deposition. While recent works have focused on CS Al alloys, less attention has been paid to CS Al binary alloys in comparison to Al engineering alloys, which have important implications for the integrity of structural components repaired by the CS process. Herein, the microstructure of CS AA5083 and Al-5.0 wt.% Mg binary alloy was analyzed by various microstructure characterization techniques. Corrosion behavior was assessed using electrochemical and immersion tests in 0.6 M NaCl (pH 8.3 and 11.5) solution. Intermetallic phases, such as Fe- and Si-containing phases, in CS AA5083 decreased corrosion resistance by increasing cathodic kinetics in near-neutral solution. In addition, immersion tests demonstrated lower corrosion resistance in CS AA5083 than in CS Al-5.0 wt.% Mg whereas an alkaline environment showed the presence of a secondary passive layer on CS AA5083, providing higher corrosion resistance compared to CS Al-5.0 wt.% Mg.

Comparing the Corrosion Behavior and Microstructure of a WE43 Mg Alloy in Simulated Body Fluids Under Different CO2 Conditions

With the low density and high specific strength, magnesium (Mg) alloys are lightweight alloys with various applications. In addition, combined with biocompatibility, similar mechanical properties to human bones, and unique biodegradability, Mg alloys are promising biodegradable implant materials for orthopedic surgeries. However, the degradation rates of Mg alloys are too fast in physiological environments, which limits the clinical applications of Mg implants. Therefore, understanding the corrosion behavior in physiological environments is crucial for developing biodegradable Mg alloys.During Mg alloy degradation, hydroxide (OH-) ions are generated, and the pH near the alloy surface increases. Since carbonate-bicarbonate (CO3 2--HCO3 -) is a vital pH buffer system in the human body, the corrosion behavior of Mg alloys would be affected by the CO2 concentrations of the test environments. In this study, we performed electrochemical and corrosion tests of a solution heat-treated WE43 (Mg-4 wt%Y-3 wt%Nd) alloy in Hanks’ balanced salt solutions (HBSS) at 37°C. By performing the tests in air and in an incubator maintained at 5% CO2, the effect of carbonate-bicarbonate pH buffering on the corrosion behavior and corrosion microstructure of the WE43 Mg alloy was investigated.When testing the WE43 Mg alloy in air, a general corrosion morphology was observed during the 24-hour immersion. In contrast, WE43 Mg alloy tested in the incubator shows a more active surface potential and localized corrosion initiates on the alloy surface in the early stages of immersion. Electrochemical impedance spectroscopy (EIS) analysis shows that WE43 Mg alloy tested in air has better corrosion resistance than in the incubator. Furthermore, the corrosion resistance of the alloy tested in air increases with immersion time but decreases when tested in the incubator. Potentiodynamic polarization curves after 24-hour immersion confirm that the corrosion current density (i corr) of the WE43 Mg alloy tested in the incubator is higher than that when tested in air. The difference in corrosion behavior is owing to the carbonate-bicarbonate pH buffering effect and will be discussed based on corrosion microstructure characterizations. Figure 1

Corrosion behavior of combination of laser beam welded UNS S32304 + SS304L in 3.5% NaCl solution

This study investigates the corrosion behavior of laser beam-welded UNS S32304 and SS304L in 3.5% NaCl solutions, focusing on the effects of temperature. The primary objective is to enhance the understanding of corrosion resistance in welded materials and inspire advancements in corrosion mitigation strategies. The methodology involves assessing corrosion resistance under varying temperatures and comparing the performance of laser beam welding (LBW) with that of the base metals. Scanning electron microscopy analysis reveals effective passivation, while quantitative analysis indicates differences in chloride ion coverage between the weld metal and base metals. Tafel plots and electrochemical impedance spectroscopy demonstrate enhanced corrosion potential and improved barrier properties for the weld metal. Results indicate a marginal reduction in corrosion resistance at 50 °C for both base metals. LBW metals corrosion resistance demonstrates superior performance, with only 5% reduction in breakdown potential compared to 10% in base metals. Compared to the base metal, it exhibits a substantial reduction in corrosion rate, ranging from 60 to 75%. This supports enhanced corrosion resistance and material stability. Additionally, similar results are observed after the analysis with scanning electron microscopy images, reinforcing the efficacy of LBW in improving corrosion resistance of LBW UNS S32304 and SS304L. These findings underscore the potential of LBW for applications requiring robust corrosion performance. By contributing to the understanding of the corrosion behavior of laser beam-welded materials, this study addresses a critical research gap in material science and corrosion engineering. Future research may explore long-term durability and corrosion resistance under diverse environmental conditions to further elucidate the mechanisms driving the observed differences in corrosion behavior.

Atmospheric corrosion of tin coating on T2 copper in Xiangtan, China

Atmospheric corrosion of tin coating on copper was explored to understand the differences in corrosion behavior between the skyward and earthward surfaces of the tin coating. Results show that average corrosion rate of the tin coating was 0.578 ± 0.051 and 1.137 ± 0.166 μm■y−1 after one year and two years of exposure in Xiangtan, China, respectively. Corrosion rate of the tin coating during the second year of exposure was higher than that during the first year. SnO2 was the main corrosion product of the tin coating. Localized corrosion vulneravbilty of the skyward surface was higher than that of the earthward surface during the first year of exposure, but it became lower than the latter during the second year. During the first year of exposure, icorr values of the skyward and earthward surfaces were relatively low, but they sharply increased during the second year of exposure.

Effects of Process-Induced Defects on the Corrosion of Additively Manufactured Stainless Steel 304L

This study investigates the impact of process-induced defects such as gas pores, lack of fusions, and surface roughness on corrosion behavior of stainless steel 304L (SS304L) fabricated by laser powder bed fusion additive manufacturing. Specimens are printed with optimized process parameters but selected from different locations on the build plate. Parallel and perpendicular surfaces to the build direction are investigated and compared with corrosion properties of wrought SS304L in 5 wt% NaCl. The results reveal significant difference in corrosion behavior among specimens due to variations in their defect features. Pitting potential, pit initiation, and growth rates are found to be influenced by specimen location on the build plate. The specimen located in downstream of the shielding gas flow shows the least corrosion resistance. While no clear trends are observed between some corrosion properties and defect features, other properties show strong correlations. For example, no trend is observed for the corrosion properties in relation to pore average area fraction. However, strong correlations are observed for the corrosion properties as functions of defects maximum area. Corrosion properties linearly deteriorate as the defects maximum area increases. Roughness shows a mixed relationship with pitting potential. Comprehensive discussions on all these effects are presented.

A comparative study on the corrosion behavior of Q235 steel in saturated acidic red and yellow soils

Purpose The purpose of this paper is to study the corrosion behavior of Q235 steel in saturated acidic red and yellow soils. Design/methodology/approach The corrosion behavior of Q235 steel in saturated red and yellow soils was compared by weight-loss, SEM/EDS, 3D ultra-depth microscopy and electrochemical measurements. Findings Rp of the steel gradually increases and icorr gradually decreases in both the red and yellow soils with time. The Rp of the steel in the red soil is lower, but its icorr is higher than that in the yellow soil. The uniform corrosion rate, diameter and density of the corrosion pit on the steel surface in the red soil are greater than those in the yellow soil. Lower pH, higher contents of corrosive anions and high-valence Fe oxides in the red soil are responsible for its higher corrosion rates and local corrosion susceptibility. Originality/value This paper investigates the difference in corrosion behavior of carbon steel in saturated acidic red and yellow soils, which can help to understand the mechanism of soil corrosion.

Synergistic effects of grain sizes on the corrosion behavior and mechanical properties in a metastable high-entropy alloy

Synergistic effects of grain sizes on corrosion behavior and mechanical properties of metastable high-entropy alloys (HEAs) were studied. The results exhibit that the corrosion resistance of metastable HEA increases first and then decreases with grain size increases. This difference in corrosion behavior is manifested in different degrees of passive film dissolution and pitting corrosion, and ascribed to characteristics of passive film induced by different grain boundary densities. Moreover, increasing the grain size decreases mechanical strength, suggesting a strong trade-off in matching corrosion resistance and mechanical properties. The potential corrosion mechanism and trade-off between corrosion resistance and mechanical properties were discussed.

Study of short-term corrosion behavior of Q345 steel in marine atmospheric environment

This work studied the corrosion behavior law of Q345 steel exposed to 120 days in Qingdao marine atmospheric environment and the differences in corrosion behavior between the sunlit and shaded sides. The corrosion behavior law of Q345 steel was studied in detail by using weight loss method, electrochemical test, SEM, XRD and ultra-depth microscope. We found that the weight loss curve of Q345 steel under short exposure time still conforms to the power function form, and the corrosion rate increases in the early stage (15 d, 30 d) and decreases in the later stage. The change trend of polarization resistance (Rp) and corrosion current density (Icorr) obtained by electrochemical test corresponds to it. There are significant differences in the morphology and phase composition of the corrosion products of Q345 steel sunlit and shaded sides. On the one hand, the color of the rust layer is not the same, and the rust layer of the shaded side is loose and easy to fall off, and the corrosion is more serious. The three-dimensional morphology map after rust removal showed that Q345 steel had obvious local corrosion in the early stage of corrosion, and the depth of the corrosion pit on the shaded side was greater than that on the sunlit side. On the other hand, the ratio of (β + s)/γ * on the shaded side was greater than that on the sunlit side, and the protection ability of the rust layer on the shaded side was weak. The corrosion characteristics of Q345 steel are different between the sunlit side and the shaded side, and the corrosion of the shaded side is more serious. In engineering applications, we should consider the consequences of this phenomenon.

Corrosion of 316L & 316H stainless steel in molten LiF-NaF-KF (FLiNaK)

The corrosion behavior of 316L and 316H stainless steels (low and high carbon, respectively) in molten LiF-NaF-KF (FLiNaK) salt at 700 °C for 500 h has been investigated. Tests were performed in 316L stainless steel, pyrolytic boron nitride, and glassy carbon capsule materials. The capsule material had a notable effect on the corrosion behavior of the two stainless steels. The modes of corrosion for the two types of stainless steel in various capsule materials were classified into three categories, namely, uniform surface recession, selective grain boundary Cr dissolution, and the dissolution of Cr in the bulk grains. By most metrics, the 316H stainless steel exhibited slightly superior corrosion resistance, while by others the two stainless steels were comparable. These differences in corrosion behavior are attributed to the differences in grain size and the degree of sensitization.

Comparison of the Three-Phase Corrosion Behavior of SiN and 304L Stainless Steels in 6 M Nitric Acid Solution at Different Temperatures

In this work, the three-phase corrosion behavior of SiN and 304L stainless steels was comparatively investigated in a 6 M nitric acid solution at different temperatures. It was found that the corrosion rates of both steels in the liquid phase, vapor phase and condensate phase of nitric acid showed an increasing trend with rising temperature. Meanwhile, there also existed some differences in the corrosion kinetics and the corrosion resistance in the different phases of nitric acid. The corrosion rate of SiN and 304L stainless steels in the liquid phase of nitric acid had a cubic function relationship with temperature, and SiN stainless steel presented better corrosion resistance without intergranular corrosion (IGC) compared with 304L stainless steel with IGC at 100 °C and 120 °C. By contrast, the SiN stainless steel displayed a lower corrosion resistance than 304L stainless steel in the vapor phase of nitric acid at the same temperature, and the corrosion rates of SiN and 304L stainless steels showed a quadratic function relationship with temperature, indicating a milder corrosion in the vapor phase in comparison with that in the liquid phase of nitric acid. In the condensate phase of nitric acid, there was a similar corrosion behavior of the two steels to that in the nitric acid vapor phase, and 304L stainless steel also demonstrated a better corrosion resistance than SiN stainless steel at the same temperature. The differences in corrosion behavior between the two steels could be attributed to the changed media environment and the different alloy composition, and the two aspects were discussed in detail based on relevant experimental results. This work can provide an important insight into the material selection for reprocessing equipment and the development of new corrosion-resistant materials used in spent fuel reprocessing.

Electrochemical corrosion behaviour of four low-carbon steels in saline soil.

In this paper, the electrochemical corrosion behaviour of Q235, X65, X70, and X80 low-carbon steel was systematically studied by a variety of test techniques using natural saline soil containing 1.1% salt under laboratory conditions. The electrochemical corrosion behaviour, macro-micro corrosion morphology, and corrosion product composition of these four low-carbon steels in saline soil were studied to explore their salt corrosion resistance and reveal their corrosion mechanisms. The research results showed that oxygen absorption corrosion occurred in all four low-carbon steels in the saline soil, and the corrosion types were all localised corrosion. The corrosion process of Q235 steel was controlled by mass transfer, while the corrosion processes of X65, X70, and X80 steel were controlled by charge transfer. The corrosion rates of these four low-carbon steels in saline soil followed the order Q235 > X65 ≈ X70 > X80. Variation in elemental composition was the main reason for this difference in corrosion behaviour. Finally, microscopic test results showed that local corrosion pits were present on the surface of the steel sheet specimens, and the uniformity and compactness of the corrosion product accumulation were poor.

Electrochemical Corrosion Behavior of Pure Mg Processed by Powder Metallurgy

Pure Mg samples were prepared by powder metallurgy using the cold and hot compacting methods. Cold compacted pure Mg (500 MPa/RT) was characterized by 5% porosity and the mechanical bonding of powder particles. Hot compacted samples (100 MPa/400 °C and 500 MPa/400 °C) exhibited porosity below 0.5%, and diffusion bonding combined with mechanical bonding played a role in material compaction. The prepared pure Mg samples and wrought pure Mg were subjected to corrosion tests using electrochemical impedance spectroscopy. Similar material corrosion behavior was observed for the samples compacted at 500 MPa/RT and 100 MPa/400 °C; however, hot compacted samples processed at 500 MPa/400 °C exhibited longer corrosion resistance in 0.9% NaCl solution. The difference in corrosion behavior was mainly related to the different binding mechanisms of the powder particles. Cold compacted samples were characterized by a more pronounced corrosion attack and the creation of a porous layer of corrosion products. Hot compacted samples prepared at 500 MPa/400 °C were characterized by uniform corrosion and the absence of a layer of corrosion products on the specimen surface. Powder-based cold compacted samples exhibited lower corrosion resistance compared to the wrought pure Mg, while the corrosion behavior of the hot compacted samples prepared at 500 MPa/400 °C was similar to that of wrought material.

Effect of Homogenization Temperature and Soaking Time on the Microstructure and Corrosion Properties of a Twin Roll Casted AA3003

The AA3003 alloy is widely used as fin material in heat exchangers. The lifetime of these heat exchangers is mostly determined by their corrosion properties. Twin roll casting (TRC) of AA3003 material is known to often result in the formation of a macrosegregation area of alloying elements toward the center plane of the casted strip (center line segregation = CLS). Considering the potential exposure of cross-sectional areas of TRC material in the heat exchanger fin application, and the relatively high corrosion susceptibility of the CLS, the study of this region is of key importance to understand the microstructural effects on the resulting corrosion mechanisms and kinetics for these materials. Typically the alloys are homogenized to bring the microstructures closer to an equilibrium state, but the impact of this heat treatment on the corrosion properties is insufficiently studied. Therefore, this study investigates the effect of different homogenization procedures on the corrosion properties of the CLS and the interaction of the intermetallic particles with the surrounding aluminum matrix. This work shows that the pitting corrosion resistance is greatly dependent on the homogenization temperature, with better corrosion resistance obtained with higher temperature, especially near the CLS. This difference in corrosion behavior is completely attributed to a difference in microstructure and not to an oxide layer effect. Furthermore, it is observed that not only temperature will have a large influence on the corrosion resistance, but duration of the heat treatment as well.

Effect of Temperature and Composition on Corrosion Behavior of Medium Cr Steel in a Salt Solution Containing CO2

In this paper, the corrosion behavior of three kinds of medium Cr low C steels in the simulated service environment of the transport pipeline was investigated through accelerated corrosion experiments, and the corrosion resistance mechanism of these experimental steels at different temperatures was investigated by electrochemical means. Finally, the reasons for the difference in corrosion behavior were analyzed from the grain boundary and surface Volta potential. The results show that as the temperature rose, the corrosion rate of the 5Cr specimen increased sharply and the corrosion type developed from slight general corrosion to severe general corrosion. The 7Cr specimen was less sensitive to temperature, and the type of corrosion changed from slight general corrosion to local corrosion. Finally, the 9Cr specimen was not sensitive to temperature, and the type of corrosion was always local corrosion. 5Cr steel could form a protective product film at 30°C. As the temperature rose, the protective ability of the product film decreased, and the matrix dissolved easily. The film of 7Cr and 9Cr samples had not yet precipitated and the matrix was difficult to dissolve at 30°C. However, the matrix dissolved easily at 50°C, and the product film had formed, which played a major role. At 70°C, the protective effect of the product film decreased, and the gap between the 7Cr and 9Cr samples began to appear. The increase of Cr content helped to refine grains and increased the proportion of low-angle grain boundaries. At the same time, the increase of Cr element helped to increase the maximum Volta potential of the experimental steel and increased the Volta potential difference. As a result, the test steel was shown to be resistant to uniform corrosion, but it also increased the risk of pitting corrosion.

Protective films of stearic and octadecylphosphonic acid formed by spray coating

Spray coating formation of stearic and octadecylphosphonic acid films for corrosion protection of cupronickel alloy was studied in this work as a more practical alternative to widely studied dip-coating method. Protective properties of organic films formed under various experimental conditions were examined by electrochemical studies in 3% NaCl solution as a corrosive medium. Polarization resistance measurements as well as electro­chemical impedance spectroscopy were employed to follow in time the corrosion behaviour of cupronickel alloy modified by studied organic acids. It was found that among examined experimental parameters, time elapsed between two sprays and number of sprays have the strongest influence on the film stability and its protective properties. This study confirmed that it is possible to form by spray coating the films of stearic and octadecyl­phosphonic acid with protective properties that resemble to those of the films prepared by dip-coating method. Differences in corrosion behaviour of samples protected with stearic and octadecyl­phosphonic acid were attributed to difference in the bond strength between substrate and each organic acid. Studied samples were also examined by the scanning electron microscopy. Fourier transformed infrared spectroscopy studies showed that crystalline structure dominates in studied films, while contact angle measure­ments confirmed that modified cupronickel alloy surface exhibits hydrophobic properties.

Corrosion of nanocrystalline and coarse-grained nickel-iron (Ni-Fe) alloys in neutral and alkaline sulfate environments

Potentiodynamic polarization behaviour of electrodeposited nanocrystalline and conventional polycrystalline Ni-Fe alloys of similar compositions was investigated in neutral (pH 7) and alkaline (pH 10) 0.5 M Na2SO4 environments. In neutral solution, elevated current densities and delayed passivation were observed for all nanocrystalline materials, independent of composition. This behaviour was attributed to sulfur, present in the nanocrystalline materials as an impurity, more so than an effect of grain refinement. In alkaline solution, the effect of sulfur was exceeded by oxide film formation, and no significant difference in corrosion behaviour was observed as a function of grain size i.e. intercrystalline volume fraction.

Corrosion behavior of under‐, peak‐, and over‐aged 6063 alloy: A comparative study

AbstractThe mechanical property of age‐hardenable Al‐alloys is governed by the state of ageing, which determines the microstructure and consequently, their corrosion behavior which is a vital aspect for a number of applications. This article presents a comparative assessment of corrosion behavior of under‐, peak‐ and over‐aged Al‐Mg‐Si alloy. Corrosion characteristics have been determined via immersion tests in 0.1 M ortho‐phosphoric acid solution and intergranular corrosion (IGC) tests. Corroded surfaces are examined by field emission scanning electron micrographs‐energy dispersive spectroscopy and 3D optical profilometer. The obtained results reveal that the corrosion rate at a specific immersion time as well as the depth of IGC increases in the order for under‐, peak‐, and over‐aged states. Irrespective of the state of ageing, corrosion loss increases linearly but the rate of corrosion decreases rapidly with increasing immersion time. The dominant mode of corrosion in under‐aged alloy is identified as localized pitting, while peak‐aged is highly susceptible to IGC in contrast extensive pitting corrosion is observed for over‐aged alloy. The observed differences in corrosion behavior are explained considering characteristics of precipitates. Formation of β (Mg2Si) in case of over‐aged alloy and presence of inclusions like AlFeMnSi particles are found to accelerate pitting corrosion.

A study of a non‐conventional evaluation of results from salt spray test of aluminum High Pressure Die Casting alloys for automotive components

Aim of the present work was to investigate in a non‐conventional way the results of aluminum castings salt spray tests. These experiments were engineered in order to obtain a quantitative measurement of the corrosion rate, instead of the qualitative visual analysis usually employed in the traditional salt spray test. These tests were performed on aluminum EN AC‐46000, EN AC‐44400, and EN AC‐43500 samples. A comparison was made with electrochemical tests on specimens and the traditional salt spray testing on a real dimension component. The results showed a good reliability of the new method that gave outputs in agreement with the electrochemical technique. The new concept of salt spray test data processing was able to detect very small differences in corrosion behavior of tested alloys, demonstrating higher precision and reliability in respect to the polarization technique. Such result was explained considering the adoption of specimen with larger area and longer time of exposure to the selected corrosive environment that reduce respectively the effect of uneven distribution of porosity and intermetallics in the samples, typical of aluminum castings, and the potential local and transient events related to these defects.