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• Benzotriazole corrosion inhibition on 24.5, 4.3, and 0.6 µm grain steels was studied. • Inhibition efficiency on 24.5, 4.3, and 0.6 µm grain steel is 73.6 %, 81.7 %, and 90 %. • Benzotriazole is mixed physisorbed and chemisorbed on 4.3 and 0.6 µm grain steels. • Fine grain promotes stable, dense benzotriazole film, enhancing corrosion resistance. This study investigates the adsorption mechanism, the film formation process, and the inhibition performance of benzotriazole (BTAH) on carbon steels with different grain sizes (i.e., 24.5, 4.3, and 0.6 µm) in 3.5 wt. % NaCl solution. The results demonstrate that grain refinement significantly impacts the adsorption and inhibition performance of BTAH on carbon steels. Ultra-refinement of steel grains to 0.6 µm improves the maximum inhibition efficiency of BTAH to 90.0 % within 168 h of immersion, which was much higher than that of the steels with 24.5 µm (73.6 %) and 4.3 µm grain sizes (81.7 %). Notably, grain sizes of 4.3 and 0.6 µm facilitate a combination of physisorption and chemisorption of BTAH after 120 h of immersion, as evidenced by the X-ray photoelectron spectroscopy (XPS) results and Langmuir adsorption isotherms, while BTAH adsorbed on carbon steels with a grain size of 24.5 µm through physisorption during the 168 h of immersion. Ultra-refinement of grains has beneficial impacts on promoting the formation of a stable and dense corrosion inhibitor film, leading to improved corrosion resistance and the mitigation of non-uniform corrosion. These advantageous effects can be attributed to the higher adsorption energy at grain boundaries (approximately –3.12 eV) compared to grain interiors (ranging from –0.79 to 2.47 eV), promoting both the physisorption and chemisorption of organic corrosion inhibitors. The investigation comprehensively illustrates, for the first time, the effects of grain size on the adsorption mechanism, film formation process, and inhibition performance of organic corrosion inhibitors on carbon steels. This study demonstrates a promising approach to enhancing corrosion inhibition performance through microstructural design. Carbon steels with grain sizes of 24.5 µm, 4.3 µm, and 0.6 µm were prepared via cold-rolling and annealing, and grain refinement to 0.6 µm resulted in superior adsorption and corrosion inhibition of BTA. [Display omitted] [ABSTRACT FROM AUTHOR]

This study established a circulating system to control the concentration of substances and temperature in the aqueous solution. Simultaneously, sensors were used to continuously monitor the corrosion of three pipe materials: ductile iron (DI), surface-treated ductile iron (SDI), and carbon steel (CS). A corrosion decision model based on a machine learning framework was developed for data mining. The results show that the developed model provides accurate corrosion prediction strategies. Analysis revealed that high temperature is the primary factor accelerating corrosion in water systems. SDI accelerates at 60 °C, reaching its peak at 90 °C, while DI and CS peak at 80 °C. The superior corrosion resistance of SDI is attributed to its ability to withstand accelerated corrosion under high temperatures and environmental coupling, making it more stable when immersed in water.

Galvanized steel plates with Zn–Al–Mg coatings are extensively utilized due to their exceptional corrosion resistance. This study, focusing on the cracking behavior of coatings with varying Mg/Al ratios, was conducted using in-situ tensile tests on different samples. The influence of the Mg/Al ratio on the crack resistance of the sample coatings was systematically summarized. To elucidate this point, five types of Zn–Al–Mg coatings with varying Mg/Al ratios were prepared using the same galvanizing process and tensile testing performed using a scanning electron microscope equipped with in-situ tensile capabilities. Macroscopic digital image statistical techniques were employed to quantify the extent of coating cracking, demonstrating the impact of the Mg/Al ratio on the coatings' crack resistance. The findings suggest that an increase in the Mg/Al ratio deteriorates the crack resistance of the coating, while enhancing its hardness. Moreover, this research offers a novel perspective in evaluating the crack resistance of coatings by comparing the effects of different Mg/Al ratios.

High strength low alloy steels are extensively applied in marine engineering structures (cross-sea bridge, ocean platform, etc), which are usually subjected to severe corrosion in marine atmosphere. In this work, the corrosion behaviors of 550 MPa-grade high strength low alloy marine steels with varied Si content were studied in simulated marine atmosphere. Results show the increase of Si could significantly facilitate the formation of α-FeOOH and enrichment of Cr and Cu in inner rust layer, making the rust layer compact and cation-selective. Si and Cr can be co-enriched in inner rust layer to form mixed or complex oxides with amorphous network structure, which could greatly improve the compactness and stability of rust layer and thereby enhance the corrosion resistance of low alloy steel.

ABSTRACT An electrochemical method by submersing the HRB400 rebar specimen in simulated micro pore solution (47.125 [micro]L) is proposed to rapidly evaluate the corrosion rate of HRB400 in concrete. The [...]

ABSTRACT In this paper, cyclic voltammetry technique, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and Mott-Schottky measurement combined with surface morphology observation were applied to investigate the electrochemical behavior of carbon [...]

ABSTRACT Cr modified alloy steels using HRB400 steel as base alloy were produced by remelting in a vacuum. Their corrosion resistance were estimated by open circuit potential, electrochemical impedance spectroscopy, [...]

To prevent unpredictable hazards caused by stress corrosion cracking (SCC) of bolts, a new rapid evaluation methodology was developed to assess their susceptibility under real condition. This innovative approach involved conducting fast and slow sweep electrochemical experiments and slow strain rate test (SSRT) methods to determine the potential range and correlation constant associated with SCC. To confirm solution composition in the crevice, we design a device to extract the test solution. Additionally, we investigated the correlation between SCC behaviors and applied cathodic potential by analyzing the fracture morphology of tensile specimen and employing analytical techniques such as Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS).

Corrosion resistance is a critical consideration in the selection of materials for various applications. In this study, we employed a data-driven approach using machine learning techniques and a large dataset of corrosion data to design and test four different low-alloy steels with varying amounts of tin (Sn) microalloying (0.1 wt%, 0.2 wt%, 0.3 wt% and Sn-free) for improved corrosion resistance in Beijing outdoor atmosphere. Using experimental methods such as corrosion morphology and rust layer analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and potentiodynamic polarization measurements, we verified that the 0.2 wt% Sn microalloying steel exhibited the best corrosion resistance. Our findings demonstrate the potential of data-driven approaches and machine learning techniques, such as the use of corrosion big data, in the identification and optimization of optimal alloy compositions of corrosion-resistant materials for outdoor environments.

This paper reviews the previous literature on the alloy composition design of low-density steel (LDS), focusing on the effect of Al, Mn, Ni, and other alloy elements on the formation of the steel matrix and second phase, and provides classification. The microstructure of LDS after processing includes the matrix structure, к-carbide, and B2 (FeAl, NiAl, or MnAl) phase of ferritic LDS, austenitic LDS, and dual-phase LDS. The influence of alloy elements on the corrosion resistance of LDS is derived from the addition of Al and Mn for metallurgy. Additionally, the influence of Cr and Mo addition on the corrosion resistance improvement was studied. The electrochemical properties of the corrosion process in LDS are discussed. Further, the microstructure of LDS affects the corrosion resistance properties including pitting corrosion, hydrogen embrittlement, and SCC (stress corrosion cracking). Finally, future research directions are proposed.

The effect of aluminum (Al) on the corrosion resistance of structural steels were evaluated in chlorine-containing conditions by both immersion and neutral cyclic salt spray tests as well as electrochemical measurements. The results showed that the addition of Al had different effects on the corrosion resistance. In neutral cyclic salt spray condition, sufficient oxygen content promoted the formation of stable protective layer of Al compounds. Thus, Al could enhance the compactness of rust layer, repelled the invasion of Cl−, and finally improve the corrosion resistance. However, in immersion condition, the addition of Al increased the electrochemical activity of the matrix and the number of local corrosion sites, leading to the decrease of corrosion resistance.

• Corrosion big data technology was introduced in design of novel weathering steel. • Cr-addition increases the risk of localized corrosion of weathering steel. • Mechanisms for beneficial and detrimental effect of Cr element was proposed. In this work, we studied the effect of Cr element on the corrosion resistance evolution of weathering steel based on corrosion big data technology. It suggested that corrosion big data technology is suitable for evaluation of the effect of microalloying Cr element on the corrosion evolution behavior of weathering steel. New understandings prove that the effect of Cr on the corrosion process is dynamic rather than static, the processes is affected by both of the environmental factors and the electrochemical or chemical reactions in the rust layer. Besides, Cr element has both beneficial effect and detrimental effect on the corrosion resistance of weathering steel. The beneficial effect is that the general corrosion resistance of Cr-additional steel is better than that of Cr-free steel, while the detrimental effect is that localized corrosion is intensified as the increase of Cr content in the Cr-additional steel. [ABSTRACT FROM AUTHOR]

The corrosion resistance of Cr reinforced HRB400 rebar in the marine environment was investigated. The addition of Cr increases the amount of Cr(OH)3and α-FeOOH in the passivate film, resulting in a denser passivate film structure. This enhanced passivation film inhibits localized corrosion. The pitting potential and critical chloride concentration (CTL) of the steel increased with the increase in chromium content, indicating improved corrosion resistance of the steel. On the other hand, an increase in the concentration of Cl-in solution leads to a decrease in the pitting potential and resistance of the steel, which reduces the corrosion resistance. At higher Cl-concentrations, the Cl-ions form an electrochemical interface with the steel surface, resulting in a sharp decrease in the Rfvalue. In addition, the gradual decrease in solution pH leads to a decrease in the pitting potential and CTL of HRB400 and 1.5Cr steel. The corrosion resistance was also found to be reduced, pH reduction accelerated the intrusion of chloride ions, which led to a severe breakdown of the passivation film.

Atmospheric corrosion monitoring (ACM) sensors were employed to study the initial atmospheric corrosion of carbon steels over a one-month period in six outdoor dynamic atmospheric environments in China. Based on the ∼250,000 corrosion data sets collected, the environmental impacts of relative humidity, temperature and rainfall on the initial corrosion behavior of carbon steels were investigated. The results showed that rainfall was the strongest environmental factor influencing the initial atmospheric corrosion rate. Relative humidity significantly influenced the corrosion of carbon steels in low-precipitation environments and non-rainfall period. [ABSTRACT FROM AUTHOR]

Irregular grains, high interfacial stresses and anisotropic properties widely exist in 3D-printed metallic materials, and this paper investigated the effects of heat treatment on the microstructural, mechanical and corrosion properties of 316 L stainless steel fabricated by selective laser melting. Sub-grains and low-angle boundaries exist in the as-received selective laser melted (SLMed) 316 L stainless steel. After heat treatment at 1050 °C, the sub-grains and low-angle boundaries changed slightly, and the stress state and strength decreased to some extent due to the decrease of dislocation density. After heat treatment at 1200 °C, the grains became uniform, and the dislocation cells vanished, which led to a sharp decline in the hardness and strength. However, the ductility was improved after recrystallization heat treatment. The passive film thickness and corrosion potential of the SLMed 316 L stainless steel decreased after heat treatment, and the pitting potential also decreased due to the accelerated transition from metastable to steady-state pitting; this accelerated transition was caused by the presence of weak passive films at the enlarged pores after heat treatment, especially for an adequate solid solution treatment. [ABSTRACT FROM AUTHOR]

The passive behavior of 2205 duplex stainless steel (DSS) and its individual phases (α-phase, γ-phase) in neutral 3.5% NaCl solution was investigated by various electrochemical methods. The results indicated that galvanic effect between α and γ phases cannot deteriorate local corrosion, but favors the enhancement of the passive film. Under the galvanic effect, the diffusion of the dissolved passive cations would be promoted in a short distance between α and γ zones, leading to modifications of the chemical composition and semiconductive property of the passive film and therefore the enhancement of the corrosion resistance of DSS 2205. [ABSTRACT FROM AUTHOR]

•New low alloy steel resistant to corrosion is developed for steel rebar.•Cr modified steels exhibit lower corrosion rates in macrocell corrosion test.•Cr increases the content of α-FeOOH and reduces the content of γ-FeOOH.•Marine field test consistent with results of the indoor accelerated test.

Nanocrystalline nickel coatings with grain size of 50 nm were annealed in vacuum at 200 °C and 400 °C for 10 min. Their microstructures were investigated by transmission electron microscopy (TEM). And their corrosion behaviors were studied by means of polarization and electrochemical impedance spectroscopy (EIS). The results showed that their grain size grew up to about 60 nm (200 °C) and 500 nm (400 °C), respectively. The specimen annealed at 200 °C possessed higher density of twins in compared with the counterparts of as-deposited and annealed at 400 °C. The normal grain size effect on the corrosion behavior was not observed. However, it was found that the corrosion resistance of the coating linearly changed with the density of twins. [ABSTRACT FROM AUTHOR]

Nickel coatings with different microstructures were synthesized by pulse jet electrodeposition technique. Their morphology and microstructure were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The corrosion property of the coatings was studied by using polarization, electrochemical impedance spectroscopy (EIS), potential of zero free charge (PZFC) measurements and Mott–Schottky ( M–S ) relationship. The results showed that the coating with grain size of 50 nm possessed higher corrosion resistance than that with grain size of 10 nm. This abnormal behavior may be related to the existence of nanoscale twins in the coatings and the lower concentration of acceptor in the passive films. [ABSTRACT FROM AUTHOR]

New steels with different carbon contents were self-developed by thermo-mechanical controlled processing. The effects of the carbon content and the microstructure on the corrosion properties of new steels were investigated by immersion test and SEM. The results indicated that the ferrite phase (both the proeutectoid and eutectoid ferrite) dissolved preferentially. Cementite reserved and accumulated on the surface. As carbon content increased, the content of ferrite decreased and cathode/anode area ratio increased. Therefore, the corrosion rate of new steels increased from 0.30 to 0.90 mm/years when the carbon content rose from 0.05 to 0.13 wt%. The corrosion process of new steels was studied using electrochemical impedance spectroscopy experiments during 72 h. It indicated that the impedance modulus |Z|0.01 Hzof the new steels reduces with the increase of the immersion time. While the corrosion process of the new steel with 0.11 wt% C developed faster than that with 0.07 wt% C, although their |Z|0.01 Hzwas similar at the initial stage.

A new type of corrosion-resistant steel consisting of ferrite and bainite phases was developed for cargo oil tanks of crude oil tankers. The corrosion rate of this new steel was 0.22 mm/a, which was equivalent to ca. 1/5 of the criterion (= 1 mm/a) for corrosion-resistant steels. The composition and element distribution of the corrosion products were investigated by micro-Raman spectrometry and energy dispersive spectrometer. The results demonstrated that the corrosion product was composed of a-FeOOH, Fe3O4and a continuous Cu enrichment layer. This kind of corrosion product was protective to the steel matrix and accounted for the enhancement of the corrosion resistance of the new developed steel.

The reinforced concrete structures have to survive high temperature and carbonation at low latitude region. The research on the effect of temperature and the effect of carbonation are vital to the corrosion of the rebars in concrete structures. The coupled effect of temperature and carbonation on the corrosion of rebars was researched by using the open circuit potential (OCP), the electrochemical impedance spectroscopy (EIS), and the potentiodynamic polarization (PP) measurement in the simulated concrete pore solutions (SPSs). The high temperature environment is conducive to the formation of passivated surface of rebars in SPSs, but the dissolution velocity of passivated surface is higher. The rebars have the greater capacity of passivity at lower temperature. The corrosion rate of rebars at higher temperature is smaller in moderate pH value (10.6) SPSs. The rebars suffer from serious corrosion in the pH = 9.6 SPSs at 318 K temperature.