Prediction model for corrosion rate of low-alloy steels under atmospheric conditions using machine learning algorithms

This work constructed a machine learning(ML)model to predict the atmospheric corrosion rate of low-alloy steels(LAS).The material properties of LAS,environmental factors,and exposure time were used as the input,while the corrosion rate as the output.6 dif-ferent ML algorithms were used to construct the proposed model.Through optimization and filtering,the eXtreme gradient boosting(XG-Boost)model exhibited good corrosion rate prediction accuracy.The features of material properties were then transformed into atomic and physical features using the proposed property transformation approach,and the dominant descriptors that affected the corrosion rate were filtered using the recursive feature elimination(RFE)as well as XGBoost methods.The established ML models exhibited better predic-tion performance and generalization ability via property transformation descriptors.In addition,the SHapley additive exPlanations(SHAP)method was applied to analyze the relationship between the descriptors and corrosion rate.The results showed that the property transformation model could effectively help with analyzing the corrosion behavior,thereby significantly improving the generalization ability of corrosion rate prediction models.

Effect of Ni on the corrosion resistance of bridge steel in a simulated hot and humid coastal-industrial atmosphere

The corrosion resistance of weathering bridge steels containing conventional contents of Ni(0.20 wt%, 0.42 wt%, 1.50 wt%) and a higher content of Ni(3.55 wt%) in a simulated hot and humid coastal-industrial atmosphere was investigated by corrosion depth loss, scanning electron microscopy–energy-dispersive X-ray spectroscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical methods. The results showed that, with increasing Ni content, the mechanical properties of the bridge steel were markedly improved, the welding parameters were satisfactory at room temperature, and the corrosion resistance was enhanced. When the Ni content was low(≤0.42 wt%), the crystallization process of the corrosion products was substantially promoted, enhancing the stability of the rust layer. When the Ni content was higher(~3.55 wt%), the corrosion reaction of the steel quickly reached a balance, because the initial rapid corrosion induced the formation of a protective rust layer in the early stage. Simultaneously, NiO and NiFe_2O_4 were generated in large quantities; they not only formed a stable, compact, and continuous oxide protective layer, but also strongly inhibited the transformation process of the corrosion products. This inhibition reduced the structural changes in the rust layer, thereby enhancing the protection. However, when the Ni content ranged from 0.42 wt% to 1.50 wt%, the corrosion resistance of the bridge steel increased only slightly.

Quantifi cation of the Atmospheric Corrosion of 304 and 2205 Stainless Steels Using Electrochemical Probes Based on Thevenin Electrochemical Equivalent Circuit Model

Stainless steel(SS)is one of the most widely used engineering materials in marine engineering.However,its corrosion in the marine atmospheric environment due to the high concentration of Cl-is a problem.The SS corrosion is a threat to the development and security of marine industry;therefore,evaluating the corrosion resistance of SSs is necessary.In this work,atmospheric corrosion detection probes based on a symmetrical electrode system were used to study the corrosion behaviors of 304 SS and 2205 duplex stainless steel(DSS)in a simulated marine atmosphere.A theoretical model for electrochemical noise(EN)data analysis based on the Thevenin electrochemical equivalent circuit(EEC)model was established.The relationship between the EN characteristic parameters and the corrosion rate was obtained.The Thevenin EEC model analysis showed that the relationship between the noise resistance(Rn),the noise impedance[Rsn(f)],and the impedance modulus(|Z(f)|)was Rn≈Rsn=■.Thus,Rn and Rsn can be used as indicators for quantitative corrosion evaluation.The results of EN detection for the 304 SS and 2205 DSS showed that in a simulated marine atmospheric environment,the passive fi lms on the two SSs were relatively intact at the initial exposure stage,and their dissolution rates were slow.The corrosion resistance of the 2205 DSS was higher than that of the 304 SS.With the deposition of Cl-on the SS surface,pitting was initiated and the dissolution rate increased.The pitting initiation process on the SS surface was random,and part of the active pores could be repassivated.

Stress corrosion cracking behavior of high-strength mooring-chain steel in the SO_(2)-polluted coastal atmosphere

21Cr2NiMo steel is widely used to stabilize offshore oil platforms;however,it suffers from stress-corrosion cracking(SCC).Herein,we studied the SCC behavior of 21Cr2NiMo steel in SO_(2)-polluted coastal atmospheres.Electrochemical tests revealed that the addition of SO_(2) increased the corrosion current.Rust characterization showed that SO_(2) addition densified the corrosion products and promoted pitting.Furthermore,slow strain rate tests demonstrated a high susceptibility to SCC in high SO_(2) contents.Fracture morphologies revealed that the stress-corrosion cracks initiated at corrosion pits and the crack propagation showed transgranular and intergranular cracking modes.In conclusion,SCC is mix-controlled by anodic dissolution and hydrogen embrittlement mechanisms.

INFLUENCE OF NaCl DEPOSITION ON ATMOSPHERIC CORROSION OF A3 STEEL IN THE PRESENCE OF SO_2

The regularities of atmospheric corrosion of A3 steel deposited with different amount of NaCl exposed to the air containing 1ppm SO2 at 80%RH and 25℃ were studied in laboratory. NaCl can accelerate the corrosion of A3 steel obviously under such condition. The relationship between the weight loss of A3 steel and the amount of NaCl deposition can be well described by using a quadratic function. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy and electron dispersion X-ray analysis (SEM/EDAX) were used to characterize the corrosion products. In the absence of NaCl, FeSO4 · xH2O is the dominant corrosion products, while Fe3O4, FeSO4·H2O, β-FeOOH and γ-FeOOH dominate in the presence of NaCl.

Influence of NaCl Deposition on Atmospheric Corrosion of A3 Steel

Regularity of the initial atmospheric corrosion of A3 steel in the presence of NaCI was investigated. The results showed that NaCI can accelerate the corrosion of A3 steel. Dry mass gain of A3 steel in the presence of NaCI deposition increases with the exposure time, which can be correlated by using exponential decay function. The relationship between dry mass gain and amount of NaCI deposition at a certain exposure time follows a quadratic function. More amount of NaCI deposition will slow down the corrosion rate to some extent after exposure for a certain time. SEM/EDAX was used to characterize the corrosion surface and products. The surfaces of the NaCI treated A3 steel were obviously uneven, and some tiny crevices appear in the corrosion products that could help O2 transmit to the inner layer. The amount of oxygen in atomic percentage in the corrosion products increases with the amount of NaCI deposition.

ATMOSPHERIC CORROSION OF 304AND 316 STAINLESS STEELS

Atmospheric corrosion of 304 and 316 stainless steels was studied by field exposure test, in which rain water was collected and analyzed by atomic absorption spectroscope (AAS). Emphasis was put on the dissolution of chromium and nickel from the stainless steels by atmospheric corrosion and rain runoff. AAS analyses shows that the amounts of yearly chromium and nickel dissolution were less than 150ng/cm 2 and 50ng/cm 2 respectively for both 304 and 316 stainless steels. XPS analysis reveals the marked Cr enrichment on the 316 stainless steel after one year field exposure. SEM shows the morphology of corrosion pits on the steel surfaces.

Kinetics of Atmospheric Corrosion of Mild Steel in Marine and Rural Environments

In continuation of the extensive studies carried out to update the corrosion map of India, in this study, the degradation of mild steel by air pollutants was studied at 16 different locations from Nagore to Ammanichatram along the east coast of Tamilnadu, India over a period of two years. The weight loss study showed that the mild steel corrosion was more at Nagapattinam site, when compared to Ammanichatram and Maravakadu sites. A linear regression analysis of the experimental data was attempted to predict the mechanism of the corrosion. The composition of the corrosion products formed on the mild steel surfaces was identified by XRD technique. The corrosion rate values obtained are discussed in the light of the weathering parameters, atmospheric pollutants such as salt content ＆ SO2 levels in the atmosphere, corrosion products formed on the mild steel surfaces.

Atmospheric Corrosion of Steel A3 Deposited with Ammonium Sulfate and in the Presence of Sulfur Dioxide

A laboratory study of the atmospheric corrosion of carbon steel deposited with (NH4)2SO4 in the presence of SO2 is reported. The different levels of (NH4)2SO4 (0, 15, 30, 45, 60 μg·cm-2) were added on the surface of the samples before the exposure. The corrosion was investigated by a combination of gravimetry, Fourier transform infrared spectroscope and scanning electron microscopy. A detailed knowledge about the corrosion products was acquired, both quantitatively and qualitatively. The results show that the metal loss increased and the increasing tendency of corrosion rates slowed down with the increasing exposure time. The phase constituents of the corrosion products are mainly α-FeO(OH), γ-FeO(OH), and δ-FeO(OH).

Effect of CO_2 on Atmospheric Corrosion of UNS G10190 Steel under Thin Electrolyte Film

The atmospheric corrosion of UNS G10190 steel under a thin electrolyte film in the atmosphere polluted by CO_2, has been studied in the lab using an atmospheric corrosion monitor (ACM) in combination with XRD and SEM observations of the surface of steel. The ACM study indicated that the corrosion rate of the steel increased with increasing carbon dioxide concentration. The XRD and SEM observations showed that no carbonate was found in the corrosion product on the steel surface. The corrosion product consisted of two layers, i. e., inner and outer layer. From the experimental results, it was concluded that CO_2 played an enhancing role in the atmospheric corrosion of UNS G10190 steel. The film of the corrosion product showed slight protection.

Atmospheric Corrosion Studies of Ductile Iron and Austenitic Stainless Steel in an Extreme Marine Environment

This paper presents the corrosion characteristics and the accompanying changes in the microstructure of unalloyed duc-tile iron (DI) and austenitic stainless steel (ASS) in table salt medium representing an upper limit in an extreme marine environment. The individual corrosion rates of DI and ASS was evaluated for the maximum time period of 1200 hr. Using the immersion test technique, the corrosion rate of DI was evaluated and found to be four-orders of magnitude greater than that of ASS. The corrosion product morphologies of the DI showed that the nodular matrix was gradually covered up as immersion time progressed while the corrosion channels and volume of pits that initially formed in ASS respectively deepened and increased with increased exposure time. This work is important as a reference point for the quantification of the corrosion effectiveness of alloying DI. The microstructures of the corroded samples showed corro-sion initiation and gradual accumulation of corrosion products.

Atmospheric corrosion behavior of Nb-and Sb-added weathering steels exposed to the South China Sea

The atmospheric corrosion behavior of new-type weathering steels(WSs)was comparatively studied,and the effects of Nb and Sb during corrosion were clarified in detail through field exposure and characterization.The results showed that the addition of Nb and Sb played positive roles in corrosion resistance,but there was a clear difference between these two elements.Nb addition slightly improved the rust property of conventional WS but could not inhibit the electrochemical process.In contrast,Sb addition significantly improved the corrosion resistance from the aspects of electrochemistry and rust layer.Compared with only 0.06wt%Nb,the combination of 0.05wt%Sb and 0.06wt%Nb could better optimize the rust structure,accelerate the formation of a high proportion of dense and protectiveα-FeOOH,repel the invasion of Cl^(−),and retard the localized acidification at the bottom of the pit.

Atmospheric corrosion of carbon steel in acid rain by accelerated weathering test

In this work, the accelerated weathering test of immersion-wet-dry combined cycles was carried ont. The artificial acid rain of NaHSO3-(NH4)2SO4-H2SO4 solution system was selected as immersion solution. Acidity of artificial acid rain affected corrossion weight loss of carbon steel, and pH 4.1 was found to be a critical point. Anodic reaction resistance of the samples during accelerated weathering test increased with exposed time by electrochemical measurement.

Northeastern Brazilian Marine Atmospheric Corrosion Performances of Galvanized Steel and Copper Specimens

Copper, in turn, is the most useful material in the field of electricity, especially in electrical contacts. Already, the zinc is the most useful metal in atmospheric exposure conditions which is used in sheet form as castings, but whose most important application is as a coating for corrosion protection of steel structures. Salvador, it has disadvantages as an environment conducive to corrosion, by setting up a wet surface time t4, high corrosive environment （C4）. This work was proposed to study the performance of these metals compared to the effects of air pollution of an industrial site. For both atmospheric corrosion sites （ACS） were implanted natural weathering standard in order to assess the aggressiveness of atmospheric contaminants on the performance of metal specimens （galvanized steel and copper）. In determining their corrosion rates which were analyzed for sulfate and chloride ions, atmospheric, given the proximity of this ACS to the seafront, due to these propitiate the acceleration of corrosion. The results allowed observation that the average local concentration of the sulfate was higher than the chloride, because of the proximity of the pollutant source, and that the corrosion rate of galvanized steel was more significant than 61.5% of copper.

Anticorrosive Properties of Hot-Dip Galvanized Weathering Steel in Atmospheric Exposure

Hot-dip galvanized steel is one of the most used materials in equipment and metallic structures of the Brazilian electric sector. Although carbon steel is the main substrate in the galvanizing hot-dip process, recently, weathering steel has been used as an alternative material to be galvanized. In the transmission line segment of the Brazilian electric sector, for instance, compact towers made of galvanized weathering steel have been installed to conduct energy through urban sites. It is well known that weathering steel, depending on wet and dry cycles and on the pollutants present in the atmosphere, develops a protective patina made of its corrosion products. The patina is dense and strongly adhered to the substrate, blocking the active surface and, thus, reducing the corrosion rate of the base metal. However, when the weathering steel is galvanized, the substrate surface has a layer of zinc and zinc-iron intermetallic alloys. When the sacrificial layer is consumed by atmospheric corrosion, critical questions remain to be answered regarding the underlying substrate. Will the patina of weathering steel be formed? In what condition? Does the hot-dip galvanizing process modify the weathering steel microstructure? The present work carried out an experimental research to shed light on the anticorrosive behavior of hot-dip galvanized weathering steel, after the zinc layer is corroded. This was done by a controlled pickling process, where the zinc layer was removed simulating its consumption during real corrosion processes. The results, obtained through electrochemical techniques and different accelerated corrosion tests, showed that galvanizing weathering steel is a promising technology to enhance the lifetime of structures used in the Brazilian electric sector.

Corrosion behavior and corrosion products of a low-alloy weathering steel in Qingdao and Wanning

A newly developed low-alloy weathering steel has been exposed in two coastal sites （Qingdao in the north, Wanning in the south） in China for one year. The samples in Wanning corroded far more seriously than those in Qingdao. The rust layer formed on the steel was analyzed by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, N2 adsorption approach, polarization curves, and electrochemical impedance spectroscopy （EIS）. The rust formed in Qingdao contains more X-ray amorphous compounds and is more compact than that formed in Wanning. Cr and Cu are enriched in the rust layer near the steel matrix, and the phenomenon is more obvious in Qingdao than in Wanning. The rust layer formed in Qingdao suppresses the anodic and cathodic reaction more remarkably than that formed in Wanning does. The rust layer formed in Qingdao possesses a higher ability to block the permeation of chloride ions than that formed in Wanning does.

Characterization of Rust Layer Formed on Low Alloy Steel Exposed in Marine Atmosphere

The iron rust phases formed on low alloy steels containing different quantities of Cr element have been characterized using EPMA, Raman spectroscopy, TEM, optical microscopy etc. The ion selective properties of synthesized rust films with the same phase constituent as the atmospheric corrosion products were investigated using self-made apparatus. The results showed that corrosion loss of steels exposed in marine atmosphere decreased rapidly as the Cr content of the steel was increased. Cr-containing steels were covered by a uniform compacted rust layer composed of fine particles with an average diameter of several nanometers. Inner rust layer of Cr-containing steel (2 mass fraction) was composed of a-CrxFe1-xOOH, with Cr content of about 5 mass fraction. Such rust layer showed cation selective property, and could depress the penetration of Cl- to contact substrate steel directly.

Incubation and development of corrosion in microstructures of low alloy steels under a thin liquid film of NaCl aqueous solution

Electrochemical measurement, optical microscopy, and scanning electron microscopy were employed to investigate the corrosion behavior of some low alloy steels. The steels were held under a thin liquid film of 0.5wt% NaCl aqueous solution. It is found that the steels with the same chemical composition but different micmstructures exhibit obviously different corrosion behaviors. However, the corrosion behavior of the steels with different compositions but the same microstructnres may be similar in the present investigation. The corrosion rate of bainite is slower than that of ferrite and pearlite. The corrosion products of bainite are uniform and fine. The size of carbon-rich phases produces a great impact on the corrosion of the steels, whether in the initial stage or in the long tenn. It is easy to induce large pitting for carbon-rich phases with large size, which damages the compactness of the rust layer.

Corrosion behavior of 907 steel under thin electrolyte layers of artificial seawater

The corrosion behavior of 907 steel under thin electrolyte layer(TEL) has been investigated by means of cathodic polarization curve measurement, electrochemical impedance spectroscopy(EIS) and scanning electron microscopy(SEM). The results show that the cathodic diffusion current density presents the variation trend of initial increase and subsequent decrease with the decrease of TEL thickness, and the maximum deposits at 58 μm. The cotangent-hyperbolic impedance(O) is rationally first introduced to study the diffusion process of the reactants through the corrosion products layer with many permeable holes. The initial corrosion rate of 907 steel under different TEL thickness increases with the decrease of TEL thickness except that of 104 μm,whereas the corrosion rate after long time corrosion can be ranked as 104 μm﹥402 μm﹥198 μm﹥301 μm﹥bulk solution.

Deposition of SiO_x on Metal Surface with a DBD Plasma Gun at Atmospheric Pressure for Corrosion Prevention

In this study, SiOx films were deposited by a dielectric barrier discharge （DBD） plasma gun at an atmospheric pressure. The relationship of the film structures with plasma powers was investigated by Fourier transform infrared spectroscopy （FTIR）, and scanning electron microscope （SEM）. It was shown that an uniform and cross-linking structure film was formed by the DBD gun. As an application, the SiOx films were deposited on a carbon steel surface for the anti-corrosion purpose. The experiment was carried out in a 0.1 M NaCl solution. It was found that a very good anti-corrosive property was obtained, i.e., the corrosion rate was decreased c.a. 15 times in 5% NaCl solution compared to the non-SiOx coated steel, as detected by the potentiodynamic polarization measurement.