Corrosion Behavior Of Low Alloy Steel Research Articles

Effects of Cr and Mo contents on the flow-accelerated corrosion behavior of low alloy steels in the secondary side of pressurized water reactors

Carbon steels have been extensively used as structural materials in the secondary side of pressurized water reactors, which are susceptible to flow-accelerated corrosion (FAC). To overcome this issue, low-alloy steels containing 2.25Cr-1Mo (P22) have been introduced, as Cr and Mo are effective alloying elements in mitigating FAC. However, the behavior of these alloying elements in the secondary water chemistry is not well-understood, and therefore, there is a need to explore alternative materials that can address the issue of FAC. In this study, three model alloys were manufactured based on Ducreux's model on FAC rate to examine the effects of Cr and Mo on the corrosion behavior of low-alloy steels compared to that of commercial P22. Microstructure of P22 was ferritic/pearlite structure while the model alloys was ferritic/tempered bainite structure due to the existence of Mn and Si. The difference in microstructure led to the difference in hardness values, and elimination of Mo from the model alloys resulted in reduction in strain. The FAC rate was mainly influenced by the Cr content in the oxide layer rather than Mo. The passive film layer hinders the exposure of the inner layer to H2O in the solution, resulting in Cr3+ dissolution into the Fe oxide layer. The continuous passivation leads to the formation of two compact layers, one amorphous and one crystalline Cr, creating Fe oxide substitutes. It is also revealed that the solubility of Cr species is much lower than that of Fe species resulting in the enrichment of Cr in the outer layer, and thus the higher Cr content reinforces the passivity of the steels. The Fe-Cr alloy exhibited promising corrosion resistance, suggesting that it could be a potential substitute for Fe-Cr-Mo alloy.

Study on the role of niobium in corrosion mechanism of low-alloy pipeline steel in H2S-saturated solution

In this study, the role of Nb addition on the corrosion behavior of low-alloy steel exposed to H2S solution is studied by means of microstructure, macro/microsurface morphology characteristics, type of corrosion product, cross-sectional structure and elemental distribution. The addition of Nb is a route to refine grains and improve corrosion resistance. The surface formation process of iron sulfides changes from homogeneity to dispersion at the initial corrosion stage when Nb is added to steel. However, the transformation process and crystal structure of iron sulfides are not affected by the addition of Nb. The elemental distribution of corrosion products is not affected by Nb addition although thick and compact corrosion products are formed on the specimen surface of Nb steel. A schematic model is proposed to clarify the difference of the corrosion mechanism in atomic and molecular level.

Corrosion behavior of low-alloy steel in tidal zone: A simulated investigation

Corrosion behaviors of low-alloy steel were investigated in the simulated tidal zones using stereoscopic microscope, field emission scanning electron microscope, X-ray diffraction, open circuit potential, and electrochemical impedance spectroscopy. The result shows that the corrosion in various tidal zones is much more severe than that of the immersion (IM) zone, and more severe corrosion takes place in the low tide (LT) and middle tide (MT) zones compared with the high tide (HT) zone. In the present test-time scale, uniform corrosion predominantly occurs in the IM and LT zones, and non-uniform corrosion occurs in the MT and HT zones. The main corrosion products in the LT and MT zones are Fe3O4 while α-FeOOH dominates the composition of rust layers in the HT zone.

The Effect of Polyacrylic Ester on Electrochemical Corrosion Behavior of Low-Alloy Steel in Polymer Modified Concrete Exposed to Marine Environment

The Effect of Polyacrylic Ester on Electrochemical Corrosion Behavior of Low-Alloy Steel in Polymer Modified Concrete Exposed to Marine Environment

Effect of Sb on the Corrosion Behavior of Low-Alloy Steels in a Simulated Polluted Marine Atmosphere

The effect of Sb on the corrosion resistance of low-alloy steels in a simulated polluted marine atmosphere was studied by electrochemical testing and weight loss measurements. The results showed that the addition of Sb could improve the corrosion resistance, which was confirmed by the increased polarization resistance of the steels that contained Sb. X-ray photoelectron spectroscopy analysis of the surfaces indicated that Sb participated in the formation of corrosion products and formed Sb2O5 in the rust layers. In addition, the precipitation of Sb2O5 with iron oxyhydroxides made the rust layers more uniform and compact, which provided the Sb-containing steels with better corrosion resistance than the Sb-free Steel.

Effect of Temperature on Corrosion Behavior of Low-Alloy Steel Exposed to a Simulated Marine Atmospheric Environment

The corrosion behavior of steel exposed to a simulated marine atmosphere at different temperatures (from 30 to 60 °C) has been investigated. The corroded specimens were analyzed gravimetrically and by scanning electron microscopy, x-ray diffraction and electrochemical techniques. The results revealed that the morphology of volcanic bulge can be observed on the sample surface at 60 °C, which can be attributed to the effect of temperature on the diffusion rate of ions. As the exposure temperature is increased, the relative content of the main corrosion products changed greatly. The increase in temperature not only promoted the transport of aggressive ions Cl− and the formation of local corrosion, but also affected the solubility of oxygen gas in the thin film, leading to the increase in the relative content of Fe3O4 and the acceleration of corrosion.

Corrosion rate prediction and influencing factors evaluation of low-alloy steels in marine atmosphere using machine learning approach

ABSTRACT The empirical modeling methods are widely used in corrosion behavior analysis. But due to the limited regression ability of conventional algorithms, modeling objects are often limited to individual factors and specific environments. This study proposed a modeling method based on machine learning to simulate the marine atmospheric corrosion behavior of low-alloy steels. The correlations between material, environmental factors and corrosion rate were evaluated, and their influences on the corrosion behavior of steels were analyzed intuitively. By using the selected dominating factors as input variables, an optimized random forest model was established with a high prediction accuracy of corrosion rate (R2 values, 0.94 and 0.73 to the training set and testing set) to different low-alloy steel samples in several typical marine atmospheric environments. The results demonstrated that machine learning was efficient in corrosion behavior analysis, which usually involves a regression analysis of multiple factors.

Atmospheric corrosion behavior of low-alloy steels in a tropical marine environment

The corrosion behavior of carbon steels and weathering steels was investigated in a tropical marine environment. And both exhibited similar corrosion weight-loss behavior in tropical marine environments. Corrosion weight loss (W) as a function of exposure time (t) can be calculated using the power function, W = Atn. The values of the initial corrosion rate, A, and corrosion tendency, n, can be easily obtained by taking the logarithm of the power equation. However, the corrosion rust-layer structure of the two materials was quite different. The rust layer of carbon steel presents a single-layer structure. Meanwhile, the rust layer of weathering steel exhibits a single-layer structure after exposure for about 24 months and then gradually evolves into a double-layer structure. The main corrosion products of the steels are β-FeOOH, γ-FeOOH, and Fe3O4 in the initial stage of exposure. In the rust layers, α-FeOOH appeared after 12 months of exposure.

Effect of Dissolved Oxygen on Pitting Corrosion Behavior of Low-Alloy Steel under Hydrostatic Pressure

Effect of Dissolved Oxygen on Pitting Corrosion Behavior of Low-Alloy Steel under Hydrostatic Pressure

Korozija malo legiranega jekla za fleksibilne cevi, izpostavljene morski vodi

Korozija malo legiranega jekla za fleksibilne cevi, izpostavljene morski vodi

Effects of niobium and rare earth elements on microstructure and initial marine corrosion behavior of low-alloy steels

In the present paper, the effects of Nb and rare earth elements on initial marine corrosion behavior of low-alloy steels were investigated by first principle modeling as well as multifarious analytical techniques, such as scanning electron microscopy with X-ray microanalysis (SEM/EDS), transmission electron microscopy (TEM), scanning vibrating electrode technique (SVET), and electrochemical workstation. It was found that inclusions played key roles during the corrosion process. Spherified fine (Al, RE)-oxy-sulfide inclusions were formed in RE-bearing steel, which was dissolved preferentially in 0.5 wt% NaCl solution, and inhibited the propagation of initial corrosion. In contrast, coarse Al2O3 inclusions were formed in Nb-bearing steel, thus resulting in the selective dissolution of Fe matrix and further development of initial corrosion. RE-bearing steel demonstrated higher corrosion resistance as compared to Nb-bearing steel. Moreover, the work functions of low-indexed crystallographic planes of the inclusions and the substrate were calculated by first principle modeling, and the findings indicated consistent corrosion tendencies with experimental results, (RE)2O2S > REAlO3 > Fe > Al2O3. Finally, a schematic model was proposed to observe the influences of Nb and RE elements on corrosion initiation and propagation behavior of low-alloy steels.

In Situ Study of Effect of Chromium Content and Epoxy Coating on Localized Corrosion Behavior of Low-Alloy Steel Using Localized Electrochemical Impedance Spectroscopy

In the present paper, the change in localized corrosion behavior of epoxy resin-coated low-alloy steel with varying Cr content of the steel was studied in 3% NaCl solution using localized electrochemical impedance spectroscopy (LEIS). The LEIS was operated in both frequency sweep and mapping in a single frequency mode. The characteristics of the surfaces after LEIS were observed at SEM and EDX analyses. The LEIS mapping results exhibited lower impedance values on the scratched area than that of the coated area, which signifies the higher protection of the coated surface provided by the epoxy coating. Moreover, the steel with higher Cr content has possessed excellent corrosion resistance (observed from LEIS results) due to the formation of highly stable, protective Fe- and Cr-containing duplex hydroxide (Cr2Fe(OH)2) (rust) layer on its surface. The corrosion behavior of the low-alloy steel was improved by the addition of Cr. Further, epoxy coating have provided significant support to the steel substrate against corrosion.

Effects of W and Mo Additions on Wet-dry Acid Corrosion Behavior of Low-Alloy Steels Under Different O2 Concentrations

Effects of W and Mo additions on wet-dry acid corrosion behavior of low-alloy steels under different O2 concentrations were investigated. The results showed that W and Mo-containing steels presented excellent wet-dry corrosion resistance under O2 concentrations of both 1 and 5%. The roles of W and Mo played in increasing corrosion resistance of the steels were different. W could improve the thermodynamic stability of the steel substrate, while Mo could promote the formation of protective rust. Interaction between W, Mo and O2 concentration greatly influenced wet-dry acid corrosion of low-alloy steels. W addition was more effective for depressing charge transfer process at the rust/substrate interface and presented higher enhanced effect on increasing corrosion resistance than Mo under O2 concentration of 1%. Mo was more effective on increasing rust compactness and showed higher enhanced effect on increasing corrosion resistance than W under O2 concentration of 5%.

SECM Study of Effect of Chromium Content on the Localized Corrosion Behavior of Low-Alloy Steels in Chloride Environment

This paper investigates the effect of chromium (Cr) content (0, 1, 3 and 5% Cr) in epoxy-coated alloy steel against corrosion using in situ electrochemical techniques such as EIS and SECM in a 3% NaCl solution. The EIS results revealed that the epoxy-coated Cr steel exhibited higher impedance values than carbon steel, which is attributed to the greater resistance of Cr steel toward corrosion. Based on the cyclic voltammogram results, the tip potentials were set at −0.7, 0.04 and 0.60 V for determining the concentration of dissolved oxygen at cathodic region, and oxidation of Cr2+ and Fe2+ at anodic region, respectively. The SECM measurements showed that, the tip current in the anodic region has decreased with increase in Cr content of the sample, which indicates that the oxidation of Fe2+ and Cr2+ decreases (corrosion is reduced) with the increase in Cr content of the steel. Besides, 5% Cr steel can maintain the highest corrosion resistance, and 1 and 3% Cr steels have higher corrosion resistance than the 0% Cr steel. This higher corrosion resistance of Cr steel samples could be due to the formation of Cr-rich hydro-oxide layers [Cr(OH)3 as a corrosion product] on the surface of the samples. Thus, the epoxy-coated Cr alloy steel has greater corrosion resistance in a chloride-containing environment than the carbon steel. Hence, epoxy-coated Cr alloy steel can be successfully used as a construction material in structures.

Corrosion Behaviour of Low-Alloy Steel with Titanium Addition Exposed to Seawater Environment

Corrosion Behaviour of Low-Alloy Steel with Titanium Addition Exposed to Seawater Environment

Corrosion Behavior of Low Alloy Steels in High-mineralized Mine Water

The corrosion behavior of low alloy steels, such as 27SiMn, 30CrMnSi, 30CrMnTi, 40Cr and Q550 was studied comparatively in high-mineralized coal mine water, tap water and NaCl solu- tion by means of immersion test, salt spray test and electrochemical methods as well as XRD and SEM with EDS. The results showed that elements Cr and Si can significantly affect the corrosion resistance of low alloy steels: in chloride containing media, Si exhibits stronger effect than Cr on the corrosion; whereas in the presence of oxygen (water and gas phase), Cr exhibits stronger effect than Si. Therefore, 30CrMnTi and 40Cr have better corrosion resistance in the coal mine water. The corrosion behavior of the low alloy steels in the coal mine water depend not only on the role of alloying elements but also on the compactness of the formed limescale induced by mineral ions.

Comparison of Corrosion Behavior of Low-Alloy Steel Containing Copper and Antimony with 409L Stainless Steel for a Flue Gas Desulfurization System

Comparison of Corrosion Behavior of Low-Alloy Steel Containing Copper and Antimony with 409L Stainless Steel for a Flue Gas Desulfurization System

Corrosion behavior of low‐alloy steel used for pipeline at vapor‐saturated CO2 and CO2‐saturated brine conditions

Immersion experiment was carried out to investigate the CO2 corrosion behavior of low‐alloy steel used for pipeline at vapor‐saturated CO2 and CO2‐saturated brine conditions by revealing microstructure, corrosion rate, corrosion phases, surface/cross‐section morphology, and elements distribution. The results demonstrate that mass losses at both conditions are approximately linear to corrosion time with log scale, and the corrosion rate at vapor‐saturated CO2 condition is greatly lower than that at CO2‐saturated brine condition. The main corrosion phases consisting of inner layer and outer layer are Cr‐rich compounds and FeCO3 crystals, respectively. Corrosion products on the coupon surface produced at vapor‐saturated CO2 condition are formed locally, while the ones produced at CO2‐saturated brine condition deposit on the coupons surface homogeneously. That distinction is caused by the difference of formation process of corrosive solution. According to the experimental results, corrosion mechanisms of low‐alloy steel at both conditions are discussed to illustrate CO2 corrosion behavior.

Effects of alloyed Cr and Cu on the corrosion behavior of low-alloy steel in a simulated groundwater solution

The effects of Cr and Cu on the corrosion behavior of low-alloy steel have been studied by immersion tests and electrochemical measurements combined with scanning electron microscopy and analysis of polarization curves. The low-alloy steels exhibit higher uniform corrosion resistance than do carbon steel. Crevice corrosion morphology study indicated that the pit-like corrosion attack occurred only on the Cr-containing steels. The crevice corrosion tests indicated that Cr and Cu have synergistic effects on increasing the crevice corrosion of the steel.

Influence of chromium on the initial corrosion behavior of low alloy steels in the CO2–O2–H2S–SO2 wet–dry corrosion environment of cargo oil tankers

The influence of Cr on the initial corrosion behavior of low-alloy steels exposed to a CO2–O2–H2S–SO2 wet–dry corrosion environment was investigated using weight-loss measurements, scanning electron microscopy, N2 adsorption tests, X-ray diffraction analysis, and electrochemical impedance spectroscopy. The results show that the corrosion rate increases with increasing Cr content in samples subjected to corrosion for 21 d. However, the rust grain size decreases, its specific surface area increases, and it becomes more compact and denser with increasing Cr content, which indicates the enhanced protectivity of the rust. The results of charge transfer resistance (R ct) calculations indicate that higher Cr contents can accelerate the corrosion during the first 7 d and promote the formation of the enhanced protective inner rust after 14 d; the formed protective inner rust is responsible for the greater corrosion resistance during long-term exposure.