Corrosion Resistance Of Low Alloy Steel Research Articles

Corrosion behaviour and mechanism of acid-resistant steel in acidic solutions with different Cl− concentrations

This study aimed to enhance the corrosion resistance of low-alloy steel in acidic solutions with varying Cl− concentrations. A new acid-resistant steel incorporating Cu and Sb was developed. Various analyses, including immersion tests under different Cl− concentrations and pH values, corrosion weight loss tests, electrochemical tests, morphological observations, and X-ray diffraction (XRD) analysis, were conducted to investigate the corrosion behaviour and mechanism. The results show that in chlorine-containing acidic environments, acid-resistant steel undergoes chemical dissolution at the anode, with hydrogen gas precipitation at the cathode. The corrosion current density is influenced mainly by the pH and immersion time. The primary corrosion products include Fe2O3, Fe3O4, α-FeOOH, γ-FeOOH, Cu, and Sb oxides, and the intensities of the diffraction peaks of Sb2O3 and Sb2O5 increase as the pH decreases. Acid resistance primarily comes from the protective effects of Sb2O3 and Sb2O5. An increase in H+ concentration promotes uniform coverage of Sb2O3 and Sb2O5. A higher H+ concentration has a greater protective effect on the corrosion product layer than does an increased Cl− concentration, although the influence of Cu cannot be ignored.

Structure and Protectiveness of Rust Layers Grown on Low-Alloyed Steels Under Cyclic Wet/Dry Corrosion Tests

Carbon steels are widely used in various infrastructures due to their superior mechanical properties in addition to low cost, but the mechanical properties can be deteriorated when steels are corroded. It is well-known that the weathering steels where small amounts of alloying elements such as Cu, Cr, Ni, Si and Mn are included form compact protective rust layers during the long-term exposure to atmospheric environment, resulting in superior corrosion resistance. However, as some of the alloying elements such as P that are effective to improve the atmospheric corrosion resistance of carbon steel cause segregation in the solidification process during welding, the amounts of such alloying elements have been strictly limited. The segregation of additive elements can be suppressed in stir friction welding, so-called FSW, in which metallic materials are joined in a solid state, leading to the assumption that the restrictions on the types and amounts of alloying elements can be reduced when FSW is applied instead of conventional welding. In the present work, the structure and corrosion resistance of rust layers formed on various low-alloyed steels designed for FWS are evaluated. Ingots of various low-alloyed steels including Al and P, both of which have been proved to be effective to improve the atmospheric corrosion resistance of carbon steel, were prepared using a high-frequency vacuum induction furnace. The ingots were hot-rolled at 1273 K into a plate with the thickness of approximately 2 mm and then cut into specimens with the dimension of 20 mm × 30 mm. All specimens were subjected to a laboratory cyclic corrosion test according to SAE J2334 which simulates a severe coastal atmosphere environment. In the SAE J2334 test, the specimens were kept for 6 h in a tightly sealed box where the temperature and relative humidity (R. H.) were controlled at 323 K and 100%, respectively (humid stage). Then the specimens were immersed in an aqueous solution containing 0.5 mass% NaCl, 0.1 mass% CaCl2 and 0.075 mass% NaHCO3 for 15 min. (immersion stage), followed by holding for 17h 45 min. in the sealed box at 333 K and 50%R. H. (dry stage). These three stages were repeated up to 30 cycles. After the cyclic corrosion test, rust layers on the specimens were characterized with X-ray diffraction and elemental distributions in the rust layers were evaluated with energy-dispersive spectroscopy. The corrosion current density was estimated from extrapolating Tafel slopes in polarization curves measured for the specimens subjected to the cyclic corrosion test. In XRD measurements for the specimens after 30 cycles of the cyclic corrosion test, peaks derived from α-FeOOH, β-FeOOH, γ-FeOOH and Fe3O4 were found. The fraction of the components in rust layers grown on the specimens was estimated, providing the fractions: 30-50% of α-FeOOH, 20-40% of β-FeOOH, 4% of γ-FeOOH and 30-50% of Fe3O4. Among the components, the fraction of α-FeOOH which is well-known as protective rust increased with increasing the addition of Al and P in specimen. Furthermore, it was found from EDS analysis on the cross-sections of the specimens that Al and P were distributed in the rust layers formed on the specimens in which Al and/or P were included. This indicates that Al and P can be related to the imcreased fraction of α-FeOOH in rust layers. The corrosion current density decreased with increasing the amounts of Al and P in the specimens, implying that Al and P improved the protectiveness of rust layers, that is, the increased corrosion resistance of low-alloyed steels. Similar trend was found in the corrosion rate estimated by the weight-loss method. These beneficial effects of Al and P are attributed to the increased fraction of protective α-FeOOH in rust layers.

The Influence of 1 wt.% Cr on the Corrosion Resistance of Low-Alloy Steel in Marine Environments

In this study, the effects of 1 wt.% Cr addition on the corrosion behavior and mechanisms of low-alloy structural steel in a marine environment were investigated through immersion experiments, corrosion product analysis, and electrochemical experimental systems. The results demonstrate that the addition of 1 wt.% Cr significantly enhances the corrosion resistance of low-alloy steel in marine environments. The influence of Cr addition on the corrosion product layer was analyzed through rust layer morphology, cross-sectional morphology, elemental distribution, and electrochemical systems. Cr addition effectively promotes the densification of the corrosion product layer on the surface of low-alloy steel in marine environments, hindering the penetration of corrosive ions and thus improving corrosion resistance. This study’s findings can promote the optimization of corrosion resistance in low-alloy steel in marine environments and enhance its application prospects in marine environments.

Rapid formation of titanium nitride coating by atmospheric-controlled induction-heating fine particle peening and investigation of its wear and corrosion resistance

To create a coating of titanium nitride, atmospheric-controlled induction-heating fine particle peening using fine particles of pure titanium was conducted for low-alloy steel in a nitrogen atmosphere, and the surface characteristics of the treated specimens were investigated. The formation of hard titanium nitride coatings with a thickness of 100–200 μm was achieved by peening at 1373 K for 10 s and subsequent heating at 1373 K for 120 s. Titanium particles adhered to the treated surfaces during peening at the high temperature, which reacted with nitrogen in the atmosphere during the heating after peening. Ball-on-disk wear tests were conducted to examine the wear resistance of the specimens, and it was found that the created coating by AIH-FPP improved the wear resistance of low-alloy steel owing to its high hardness. The improvement was more significant at high testing temperatures because the high testing temperature and frictional heat caused oxygen in the air to react with titanium in the coating during the wear test. Immersion of the specimens into sodium chloride solution was also conducted to investigate the corrosion resistance, which revealed that the coating created improved corrosion resistance of low-alloy steel.

Corrosion resistance of low-alloy steel in concrete subjected to long-term chloride attack: Characterization of surface conditions and rust layers

Long-term corrosion behavior of a Cr-bearing low-alloy (LA) steel with different surface conditions (as-received, pickled and pre-rusted) in concrete when partially exposed to 3.5 wt% NaCl solution was measured using electrochemical impedance spectroscopy during the 8-year exposure period. According to the results of BSE/EDS elemental mapping, FT-IR and XPS measurements, the morphology and composition of different rust layers were identified for LA steel. The improved corrosion resistance of LA steel was primarily attributed to the formation of a compact and protective inner rust layer enriched with Cr and Si, which can be further protected by the mill scale.

Effect of Carbonitride Precipitates on the Corrosion Resistance of Low-Alloy Steels under Operating Conditions of Oil-Field Pipelines

An investigation into the corrosion resistance of steels with various contents of carbon and microalloying elements was carried out. It was shown that the presence of a large amount of nanosized (2–3 nm and less) precipitates of the interphase type, particularly niobium carbonitride and vanadium carbonitride, leads to a decrease in the corrosion resistance of hot-rolled sheet products. It was found that, after heat treatment of rolled products at 710 °C, the corrosion resistance of the metal is improved. One of the reasons for this is a decrease in the amount of interphase precipitates, which negatively affect the corrosion resistance of steel, while particles formed in austenite and ferrite do not have such an effect. To ensure high corrosion resistance of steels for oil-field pipelines, microalloying with niobium instead of vanadium is advisable, as well as heat treatment at temperatures above 710 °C.

Effect of Chemical Composition and Parameters of Microstructure on Corrosion Resistance of High-Strength Rolled Products from Low-Alloy Steels in Aqueous Environments

The effect of the chemical composition and microstructural parameters on the corrosion resistance of low-alloy steels serving in oilfield pipelines is studied. The causes of lowering of the corrosion resistance of the steels are determined. Recommendations are given for raising this characteristic without lowering the strength of the steels.

Improvement of the machine learning-based corrosion rate prediction model through the optimization of input features

The corrosion resistance of low-alloy steel seriously influences its performance, particularly as a class of materials widely used in marine environments. In this study, we collected the marine corrosion data of low-alloy steels and established corrosion rate prediction models with machine learning algorithms. Both the chemical composition of low-alloy steel and environmental factors were used as input features, and the random forest algorithm was selected as the modeling algorithm. Feature reduction methods, including the gradient boosting decision tree, Kendall correlation analysis and principal component analysis, were first applied to select the dominating factors on the corrosion rate. Then, we proposed two feature creation methods to convert the chemical composition features into a set of atomic and physical property features. As a result, the feature creation method crafted a model no longer limited to materials with specific chemical compositions. The machine learning-based corrosion rate prediction model also showed good prediction accuracy of the corrosion rate. This study improved the generalization ability of the corrosion rate prediction model and proved the feasibility of machine learning in corrosion resistance evaluation.

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.

Improvement of corrosion resistance of low-alloy steels by resurfacing using multifunction cavitation in water

Low-alloy steels are based on carbon steel in combination with several percent or less (in many cases, 1 mass%) alloying elements, and they offer improved resistance to corrosion at a cost slightly higher than that of carbon steel. However, these materials do not exhibit the same corrosion resistance as stainless steel. The authors have previously developed a novel multifunction cavitation (MFC) technique, which combines ultrasonic cavitation with water jet cavitation. In this study, MFC was used to modify the surface of Cr-Mo steel (SCM435) and Ni-Cr-Mo steel (SNCM630). MFC was found to improve the residual stress value of the material as the result of surface modification while also imparting high strength and superior corrosion resistance.

Effect of immersion time in a modified green death solution on the rust layer of Cu-containing low-alloy steel

The corrosion resistance of low-alloy steel containing 0.35 wt% copper, as a function of immersion time in a modified green death solution, was investigated using electrochemical methods and surface analysis. After 30 min of immersion, the steel surface was covered with a Cu-enriched film. Improvement of the film properties and increases in the corrosion resistance were realized for the immersion time up to 6 h due to the development of the Cu-enriched layer. However, the Cu particle was formed in the Cu-enriched layer for the immersion time beyond 6 h. Since the formation of the Cu particle generated a Cu-depletion region, micro-galvanic corrosion between the Cu particle and the Cu-depletion region lead to the localized film breakdown on the surface film. The localized film breakdown, which decreased the corrosion properties of the Cu-containing steel, was accelerated by the continuous formation of Cu particles in the rust layer.

Influence of mill scale and rust layer on the corrosion resistance of low-alloy steel in simulated concrete pore solution

Electrochemical impedance spectroscopy, cyclic potentiodynamic polarization measurements, and scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy were used to investigate the influence of mill scale and rust layer on the passivation capability and chloride-induced corrosion behaviors of conventional low-carbon (LC) steel and low-alloy (LA) steel in simulated concrete pore solution. The results show that mill scale exerts different influences on the corrosion resistance of both steels at various electrochemical stages. We propose that the high long-term corrosion resistance of LA steel is mainly achieved through the synergistic effect of a gradually formed compact, adherent and well-distributed Cr-enriched inner rust layer and the physical barrier protection effect of mill scale.

Increase in Corrosion Resistance in Aqueous Media of Low-Alloy Steel Used as the Main Layer of Corrosion-Resistant Bimetals

The article is devoted to a study of corrosion resistance of low-alloy steels, in relation to chemical composition, heat treatment conditions, other steel properties, and heat treatment regimes. The effect of chemical composition, degree of deoxidation, and steel cleanliness with respect to nonmetallic inclusions on steel corrosion resistance is demonstrated, including those that may be used as a main layer in corrosion-resistant bimetals.

Increasing wear and corrosion resistance of low-alloy steel by anode plasma electrolytic nitriding

Abstract In this work, we investigate the properties of the low-alloy steel (0.4% C, 1% Cr) which is obtained as a result of anode plasma electrolytic nitriding (PEN) followed by hardening in the same electrolyte. An X-ray diffractometer and a scanning electron microscopy (SEM) were used to characterize the phase composition of the modified layer and its surface morphology. Surface roughness was studied with the use of a roughness tester. The hardness of the treated and untreated samples was measured using a microhardness tester. A pin-on-disk tribometer was occupied to evaluate weight loss of the untreated and treated samples at lubricated conditions. Corrosion properties of the samples treated surfaces were evaluated using potentiodynamic polarisation tests in solution of sodium sulfate. The effect of nitriding regimes on the weight wear and corrosion resistance of treated steel is considered. It is established that competition of the anodic dissolution and iron oxidation determined the oxide layer thickness affects microhardness layer, surface roughness, and wear and corrosion resistance. The electrolyte composition (10 wt% ammonium chloride, 5 wt% ammonia) and processing mode (650 °C, 5 min) of low-alloy steels allowing one to obtain the hardened surface layer with microhardness 780 HV and with decrease in the weight loss after lubricant wear testing of 3 times or 4.6 times for dry friction are proposed. The anode PEN (800 °C, 5 min) can decrease the corrosion current density of steel in 0.05 mol/L solution of sodium sulfate by a factor of 7.7.

Influence of the pulsed plasma treatment on the corrosion resistance of the low-alloy steel plated by Ni-based alloy

This paper presents investigation results of the influence of high temperature pulsed plasma flows (HTPPF) treatment on the corrosion resistance of low-alloy steel 0.2C-Cr-Mn- Ni-Mo cladded by the rapidly quenched nickel-based alloy. A technique that allows obtaining a defect-free clad layer with a good adhesion to the substrate was developed. It is shown that the preliminary treatment of steel samples by nitrogen plasma flows significantly increases their corrosion resistance in the conditions of intergranular corrosion test in a water solution of sulfuric acid. A change of the corrosion mechanism of the clad layer from intergranular to uniform corrosion was observed as a result of sub-microcrystalline structure formation and homogeneous distribution of alloying elements in the plasma treated surface layer thus leading to the significant increase of the corrosion resistance.

Influence of chloride concentration and pre-passivation on the pitting corrosion resistance of low-alloy reinforcing steel in simulated concrete pore solution

The effect of chloride concentration and pre-passivation on the pitting corrosion resistance of low-alloy steel and conventional low-carbon steel in simulated concrete pore solution was investigated using electrochemical techniques and surface analysis measurements. The results show that the passive film could enhance the pitting corrosion resistance for both investigated steels. Low-alloy steel exhibits slightly lower pitting corrosion resistance at low chloride concentration compared to low-carbon steel, regardless of the passivation condition. However, at high chloride concentration, low-alloy steel shows higher pitting corrosion resistance due to the formation of Cr-enriched protective rust layer.

Influence of silicon addition on the mechanical properties and corrosion resistance of low-alloy steel

The addition of silicon to low-alloy steel allows to modify the materials’ microstructure and thus to improve their corrosion resistance and mechanical properties. The influence of adding different amounts of silicon on the properties (density, transverse rupture strength, microhardness and corrosion resistance) and microstructure of low-alloy steel was investigated. Samples were prepared via the mechanical alloying process, which is the most useful method to homogeneously introduce silicon to low-alloy steel. Sintering was performed by using the spark plasma sintering (SPS) technique. After the SPS process, half of each of the obtained samples was heat-treated in a vacuum furnace. The results show that high-density materials were achieved, and a homogeneous and fine microstructure was obtained. The investigated compositions containing 1 wt% of silicon had better corrosion resistance than samples with 3 wt% of silicon addition. Furthermore, corrosion resistance as well as the mechanical and plastic properties of the samples with 1 wt% of silicon can be further improved by applying heat treatment.

Development of Sulfuric and Hydrochloric Acid Dew-Point Corrosion-Resistant Steels: 1. Effect of Alloying Elements on the Corrosion Resistance of Low-Alloy Steels

Development of Sulfuric and Hydrochloric Acid Dew-Point Corrosion-Resistant Steels: 1. Effect of Alloying Elements on the Corrosion Resistance of Low-Alloy Steels

Effect of W, Mo, and Ti on the Corrosion Behavior of Low-Alloy Steel in Sulfuric Acid

The effects of W (0.05 wt% W), Mo (0.05 wt% Mo), and Ti (0.05 wt% Ti) addition on the corrosion resistance of low-alloy steel used in flue gas desulfurization systems were examined using electrochemical measurements in a 10 wt% sulfuric acid (H2SO4) solution. The corrosion rate increased in the following order: W steel < Mo steel << Ti steel. The surface analysis indicated that the type and quantity of inclusions by steel are as follows: W steel (manganese sulfide [MnS]) < Mo steel (MnS, molybdenum disulfide [MoS2]) << Ti steel (MoS2, titanium sulfide [TiS]). The corrosion rate was influenced by sulfide inclusions in the steels. In particular, the corrosion rate of Ti-containing steel was the highest due to a large number of TiS inclusions formed during the steel manufacturing or corrosion processes.

Effect of tin on the corrosion behavior of low-alloy steel in an acid chloride solution

This study examined the effect of Sn addition ranging from 0 to 0.1 wt.% on the electrochemical properties of low-alloy steel using electrochemical techniques in an acid chloride solution and surface analysis techniques. The potentiodynamic test showed the active corrosion behavior of all specimens and the corrosion rate decreased with increasing Sn addition. EIS showed that the Sn-containing steels had higher rust layer resistance. These results confirmed that the interaction of Sn with Cu and Sb improves the corrosion resistance of low-alloy steel due to the formation of the continuous tin oxide, copper oxide and antimony oxide layer.