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This paper aims to explore the transformation process and transformation mechanism of carbon steel under the marine environment.

In this paper, the transformation and rust layers corrosion products on 0Cu2Cr carbon steel with different cycles coupon test was investigated and deeply explored by scanning electron microscope, energy dispersive spectrometer, X-ray diffraction.

The results showed that the thickness of rust layers grew from 71.83 µm to 533.7 µm with increasing duration of corrosion. The initial corrosion product was γ-FeOOH, then part of the γ-FeOOH continued growing, and under the capillary action, the other part of the γ-FeOOH transformed to α-FeOOH.

To the best of the authors’ knowledge, this paper puts forward for the first time a new viewpoint of the development of corrosion products of low-carbon steel in two ways. This discovery provides a new idea for the future development of steel for marine engineering.

Some power plants in China that adopt reverse osmosis (RO) product water as their fresh water source face serious metal corrosion of their water distribution system. The corrosion process of carbon steel in RO product water is still not clear and there is no suitable anti‐corrosion method for the power plant to employ. The purpose of this paper is to study the corrosion behavior of carbon steel in RO product water, determine the factors leading to the high corrosion rate of carbon steel, and then suggest appropriate anti‐corrosion measures.

By measuring polarization curves and AC impedance values of the corrosion system and analyzing corrosion products using scanning electron microscopy (SEM), infrared spectroscopy (IR) and X‐ray diffraction (XRD), the corrosion behavior of Q235A carbon steel in the RO product water derived from seawater was studied.

The experimental results showed that the corrosion process of carbon steel in RO product water is controlled by the diffusion process of oxygen, and the corrosion products contain γ‐FeOOH, Fe₃O₄ and small amounts of α‐FeOOH. Although rust formed had a double layer structure, the outer rust layer, which contained γ‐FeOOH and a little α‐FeOOH, was thin. The inner rust layer, containing Fe₃O₄, was the main component of the rust layer. Due to the weak acidity of RO product water, γ‐FeOOH can be transformed to Fe₃O₄ very quickly and Fe₃O₄ will accumulate on the metal surface. Because of the electrical conductivity and fractured surface of the Fe₃O₄ layer, the corrosion product layer cannot inhibit the corrosion process by hindering the diffusion process of oxygen, and hence the corrosion rate of carbon steel is always high.

The paper describes the first systematic research to be carried out on the corrosion behavior of carbon steel in RO product water. It was found that the generation and accumulation of Fe₃O₄ on the metal surface was the primary reason leading to the high corrosion rate of carbon steel, and anti‐corrosion measures can be chosen following the following rules: deoxygenation, raising of the pH of the solution, or addition of corrosion inhibitors to the solution.

This paper aims to study the effect of ultraviolet (UV) light on the corrosion behavior of BC550 weathering steel in simulated marine atmospheric environment.

The effect of UV light on the corrosion behavior of BC550 weathering steel in simulated marine atmospheric environments were investigated by the corrosion weight gain experiment, in situ electrochemical noise, scanning electron microscope and X-ray diffraction.

UV light accelerated the corrosion process of BC550 weathering steel in the simulated marine atmospheric environment during the first 168 h. The maximum influence factor of UV light was 0.32, and it was only 0.08 after 168 h of corrosion process.

As the extension of corrosion time, the thickness and density of the corrosion product layer increased, which weakened the acceleration effect of UV light.

This study aims to study the effect of Sn on the corrosion behavior of weathering steel (WS) in a simulated tropical marine atmosphere.

Indoor alternate immersion tests, electrochemical measurements and real-time current-monitoring technology based on the galvanic corrosion principle were used and the scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy and electron probe microanalyzer were used to analyze the morphology and component of the rust layer.

The results indicated that Sn has a positive influence on the corrosion process. Sn participated in the composition of the rust layer in the form of SnO₂ and is enriched in the inner rust layer. SnO₂ participated in the coprecipitation process with iron oxides and oxyhydroxides, which promoted further transformation of γ-FeOOH to α-FeOOH. As a result, the rust layer of Sn-containing steel was continuous, compact and effectively blocked the invasion of aggressive Cl⁻. Therefore, the additive of Sn enhanced the corrosion resistance of WS in a simulated tropical marine atmosphere.

The corrosion behaviors of WS were researched by the real-time current-monitoring technology which was rarely used.

This paper aims to investigate the effect of alternating current (AC) on corrosion, it is not yet clear about the exact mechanism of the corrosion induced by AC. Previous reports indicated that AC corrosion was similar to the effect of continuous cathodic and anodic polarization on the corrosion process of the metals. Wan et al. studied the effect of negative half-wave AC on stress corrosion cracking behavior and mechanism of X80 pipeline steel in near-neutral solution.

This study attempted to understand the AC-induced corrosion by imposing the half-cycle AC on the X80 pipeline steel in an acid bicarbonate solution. The AC corrosion mechanism was determined by weight loss and potentiodynamic polarization curve measurements, as well as surface characterization.

The results show that the positive half-cycle AC accelerated the uniform corrosion in the NaHCO3 solution, the negative half-cycle AC would decrease the uniform corrosion and local corrosion was increased and some Ca and Mg deposited on the surface of X80 steel, so the corrosion rate decreased by negative half-cycle AC. The corrosion product was composed of α-FeOOH under the application of positive half-cycle AC. The oxygen reduction led to a local increase of pH near the electrode surface and led to the formation of α-FeOOH, which enhanced the protectability of corrosion products.

Researchers studied the effect of negative half-wave AC on stress corrosion cracking behavior and mechanism of X80 pipeline steel in near-neutral solution. However, the AC behavior and corrosion mechanism in acid solution are unknown. So to make clear about the corrosion behavior of metals in different polarization states and the mechanism involved, diode technology was used to research the AC corrosion, half-wave AC was applied on the metals after the full-wave rectified.

Transmission Mossbauer Spectroscopy of corrosion products of mild steel immersed in 3 per cent NaCl and 3 per cent NaCl containing 0.03 M concentrations of different inhibitors viz. sodium nitrite, sodium molybdate, sodium tungstate, sodium meta borate and sodium hexameta phosphate were carried out to understand the corrosion process occurring under these conditions. All corrosion products showed the presence of γ‐FeOOH and superparamagnetic (SPM) α‐FeOOH. However, the corrosion product obtained on mild steel in presence of nitrite showed non‐stoichiometric magnetite (Fe_3−xO₄) along with oxyhydroxides. The corrosion products of steel in presence of phosphate inhibitor showed the presence of ferrous phosphate. The Mossbauer results were supported by FTIR studies. Electrochemical studies showed a high polarisation resistance (Rp) in ease of nitrite inhibitors. Therefore, it can be concluded that an inhibitor which promote the formation Fe_3−xO₄ can provide better protection for steel substrate.

The purpose of this paper is to obtain the environmental factor, which has the greatest effect on the corrosion rate of Q235 carbon steel under thin electrolyte layer, and to analyze the effect of this factor on the corrosion morphology, corrosion products and polarization process of Q235 carbon steel.

An electrochemical device, which can be used under thin electrolyte layer is designed to measure the corrosion current in different environments. Response surface methodology (RSM) is introduced to analyze the effect of environmental factors on corrosion rate. Scanning electron microscope (SEM) and X-ray diffraction (XRD) technique are used to analyze the results. The Tafel slopes of anode and cathode in different humidity and solution are calculated by least square method.

The three environmental factors are ranked according to importance, namely, humidity, temperature and chloride ion deposition rate. In a high humidity environment, the relative content of α-FeOOH in the corrosion product is high and the relative content of β-FeOOH is low. The higher the humidity, the lower the degree of anodic blockage, whereas the degree of cathodic blockage is independent of humidity. The above experiments confirm the effectiveness and efficiency of the device, indicating it can be used for the screening of corrosive environmental factors.

In this paper, an electrochemical device under thin film is designed, which can simulate atmospheric corrosion well. Subsequent SEM and XRD confirmed the reliability of the data measured by this device. The introduction of a scientific RSM can overcome the limitations of orthogonal experiments and more specifically and intuitively analyze the effects of environmental factors on corrosion rates.

The eastern coast of Saudi Arabia has one of the most corrosive environments in the world. Dhahran is therefore an ideal location for the study of atmospheric corrosion. One out of every seven cars in the region is corroded. The atmosphere is contaminated by SO₂ and a high concentration of suspended particulate matter (SPM) containing sand, salt and carbon particles, exceeding the World Health Organization (WHO) and Middle East Environmental Protection Agency (MEPA) limits most of the time. Corrosion proceeds in the Dhahran atmosphere at a R.H. as low as 40 per cent. At locations close to the sea (1.5 Km), β‐FeOOH is the major corrosion product and α‐ and γ‐FeOOH with some aluminates, silicates and hydrocarbons the minor products. At a location remote from the sea α‐ and γ‐FeOOH are found to be the major corrosion products as shown by XRD and FTIR spectroscopy. The concentration of hydrogen ions, chloride ions and SO₂ appears to control the corrosion process during the initial exposure period up to one year and the adsorption of anions on the corrosion product films in the later period.

The purpose of this paper is to study the influence of temperature on the acceleration and simulation of indoor corrosion tests and the corrosion behavior of Q235 carbon steel.

The indoor corrosion test was carried out by continuous salt spray in a salt spray chamber. Weight loss analysis, X-ray diffraction, cannon 1500 D, scanning electron microscopy and electrochemical techniques are used to analyze the results.

It was found that thickness loss of Q235 carbon steel increases with higher temperature and it can reach 0.095 mm at 50°C. Compared with the Xisha exposure test, the acceleration rate can achieve 230 times. This phenomenon indicates that decreasing the experimental temperature is beneficial to the anti-corrosion of the Q235 carbon steel. It is fascinating to find that acceleration and simulation increase with temperature simultaneously, which shows that β-FeOOH promotes the corrosion rate and α-FeOOH provides high simulation. Meanwhile, electrochemical impedance spectroscopy indicates that the resistance of the rust layer improves with temperature.

Through the study, the authors found that with the increase of temperature, the acceleration and simulation of indoor corrosion test improved, corrosion products and kinetics are the same as those in outdoor exposure test, and which means that the laboratory can achieve the long-term corrosion degree of outdoor exposure in a short time, and the similarity with outdoor exposure is high. This helps to the study of marine atmospheric corrosion, and indoor accelerated corrosion tests can largely eliminate regional differences by adjusting some environmental factors, and lay a foundation for marine atmospheric corrosion.

The effects of temperature on the acceleration and simulation of indoor corrosion tests are discussed. Through laboratory experiments, the long-term service life of Q235 carbon in the Xisha marine atmosphere can be predicted effectively.

This paper aims to study the corrosion behavior of D32 steel suffered to marine splash zone. Type D32 structural steel has good mechanical properties and is commonly used for offshore oil platform construction in China. To ensure the safety of marine steel structure, it is important to study the corrosion process of D32 steel in the splash zone.

The corrosion behavior of D32 steel in splash zone environments was studied using polarization curves and electrochemical impedance spectroscopy. The electrochemical results were obtained from the corroded steel samples exposed in the splash zone of a bespoke simulate device, while corrosion morphologies and corrosion products of the steel samples were characterized using scanning electron microscopy and X-ray diffraction.

In wet–dry cyclic exposure, the reaction was a self-perpetuating process of chemical oxidation and electrochemical reduction. The rust itself took part in the reduction processes and, hence, increased the corrosion rate of the steel samples.

Finally, the corrosion process of D32 steel in splash zone is considered.