Coastal-industrial Atmosphere Research Articles

Understanding the role of alloyed Cu and P in the initial rust composition of weathering steel formed in a simulated coastal-industrial atmosphere

A combination of SR-XRD, Raman spectrum, EPMA and electrochemical measurements were used to investigate the role of alloyed Cu and P in the initial rust composition of weathering steel formed in a simulated coastal-industrial atmosphere. Results indicated that the addition of Cu inhibits the electrochemical cathodic and anodic process in the corrosion process and is beneficial to the formation of α-FeOOH in the internal rust layer. The addition of Cu and P was more effective in promoting the formation of α-FeOOH and inhibiting the formation of Fe3O4/γ-Fe2O3, resulting in the lowest corrosion rate. Data availability statementThe original/processed data required to reproduce these findings cannot be shared at this time as the data is related to an ongoing study.

The Initial Corrosion Behavior of Carbon Steel Exposed to the Coastal-Industrial Atmosphere in Hongyanhe

The Initial Corrosion Behavior of Carbon Steel Exposed to the Coastal-Industrial Atmosphere in Hongyanhe

Corrosion kinetics and patina evolution of galvanized steel in a simulated coastal-industrial atmosphere

The corrosion kinetics and patina (corrosion products) layer evolution of galvanized steel submitted to wet/dry cyclic corrosion test in a simulated coastal-industrial atmosphere was investigated. The results show that zinc coating has a greater corrosion rate during the initial period and a lower corrosion rate during the subsequent period, and the patina composition and structure can greatly affect the corrosion kinetics evolution of zinc coating. Moreover, Zn5(OH)6(CO3)2 and Zn4(OH)6SO4 are identified as the main stable composition and exhibit an increasing relative amount; while Zn12(OH)15Cl3(SO4)3 cannot stably exist and diminish in the patina layer as the corrosion develops.

Effect of tin addition on corrosion behavior of a low-alloy steel in simulated costal-industrial atmosphere

The effect of tin addition on the atmospheric corrosion behavior of a low-alloy steel in simulated coastal-industrial atmosphere has been investigated by indoor wet/dry cyclic corrosion test (CCT). The results indicate that tin addition can obviously make the steel substrate more resistant to atmospheric corrosion by suppressing the cathodic H+ reduction reaction, and but tin addition is not of obvious beneficial effect when the steel is covered with a thicker rust layer during long-term corrosion process. The reason lies in the fact that the presence of un-reduced H+ can lower the electrolyte pH value and lead to a loose and porous rust layer on tin-containing steel sample than that on tin-free steel sample. In addition, the 120 CCT cycles corrosion process of the two steels can be divided into three stages. Both the tin-free and tin-containing steels show an increasing corrosion rate during the initial corrosion stage and then exhibit a decreasing corrosion rate during the second and third corrosion stages. Moreover, tin addition makes the tin-containing steel rust layer have a higher amount of α-FeOOH and lower amount of γ-FeOOH and Fe3O4 than the tin-free steel rust layer.

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 (0.20wt%, 0.42wt%, 1.50wt%) and a higher content of Ni (3.55wt%) 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 (≤0.42wt%), the crystallization process of the corrosion products was substantially promoted, enhancing the stability of the rust layer. When the Ni content was higher (~3.55wt%), 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 NiFe2O2 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 0.42wt% to 1.50wt%, the corrosion resistance of the bridge steel increased only slightly.

A Study on the Initial Corrosion Behavior of Carbon Steel Exposed to a Simulated Coastal-Industrial Atmosphere

A Study on the Initial Corrosion Behavior of Carbon Steel Exposed to a Simulated Coastal-Industrial Atmosphere

Corrosion Mechanism Analysis of a 20<sup>#</sup> Carbon Steel Lightning Rod on a Substation

A lightning rod on a coastal substation cracked, so the related equipment is forced to be shut down. Optical microscope, spectrometer, SEM, EDS and ion chromatograph were adopted to analyze the corrosion mechanism. Results show that the lightning rod is corroded severely. The material of this lightning rod is 20# carbon steel. The corroded part and the uncorroded part are divided into two layers. Nodulizing of pearlites is evident in the microstructure of corroded area. Both of EDS and ion chromatograph detect high concentration of chloride ion and sulfate ion from the corrosion products. In this sense, corrosion is probably induced by coastal-industrial atmosphere and rainwater pollution. Besides, improper structure of the lightning rod is also a factor to cause the corrosion.

Atmospheric Corrosion of Copper Exposed in a Simulated Coastal-Industrial Atmosphere

The corrosion behavior of copper exposed in a simulated coastal-industrial atmosphere has been investigated using weight loss measurement, scanning electron microscopy, X-ray diffraction, potentiodynamic polarization and in-situ electrochemical impedance spectroscopy (EIS) with micro-distance electrodes. The results show that corrosion kinetics follows the empirical equation D = Atn. The main corrosion products are composed of Cu2O, Cu2Cl(OH)3 and Cu4Cl2(OH)6. A two-layer structure comprising a loose outer layer and a compact inner layer forms the corrosion products during corrosion process. SO2 has been found to promote the formation of Cu4Cl2(OH)6.

STRESS CORROSION BEHAVIORS OF E690 HIGH-STRENGTH STEEL IN SO2-POLLUTED MARINE ATMOSPHERE

With the development of industry, the atmosphere in many cities along the coastal lines such as Qingdao in China has been polluted with SO2, and has been changed to coastal-industrial atmosphere with the coexistence of SO2 and Cl-. The corrosion and stress corrosion cracking (SCC) behavior and mechanism of steel in this environment is different from that in the coastal atmosphere containing only Cl- or the industrial atmosphere containing only SO2. Previous study have indicated that SO2 in the marine atmosphere can greatly promote the stress corrosion cracking of high-strength steel due to acidification of thin electrolyte layer and reproduction of H+ through FeSO4. E690 steel, as a newly-developed high strength steel, is very promising to be widely used in offshore platform in the near future for its excellent performance. However, there is few research about its SCC behavfor in marine atmosphere, especially in SO2-polluted atmosphere. Therefore, it's of great importance to investigate the SCC behavior and mechanism of E690 steel in this environment. In this work, U-bend specimen corrosion test under dry/wet cyclic condition, electrochemical measurements, crack morphology observation and rust layer analysis, were conducted to investigate the effect of SO2 on SCC behavior of E690 steel in simulated SO2-polluted marine atmosphere. The results indicated that E690 steel has a high SCC susceptibility in SO2-polluted marine atmosphere with a combined mechanism of anodic dissolution (AD) and hydrogen embrittlement (HE). SO2 in the atmosphere can facilitate the densification of inner rust layer by promoting the formation of alpha-FeOOH and enrichment of Ni and Cr in the inner rust layer, leading to the concentration of Cl- under the rust layer, which may result in the initiation and propagation of SCC cracks significantly and therefore enhance the SCC susceptibility.

EFFECT OF pH VALUE ON THE CORROSION EVOLUTION OF Q235B STEEL IN SIMULATED COASTAL-INDUSTRIAL ATMOSPHERES

The atmosphere in many cities along the coastal lines such as Qingdao in China has been polluted with SO2 due to the development of industry, and the atmosphere therefore has been changed to coastal-industrial atmosphere. The corrosion behavior and mechanism of steels in coastal-industrial atmosphere with the co-existence of SO2 and Cl are different from that in the coastal atmosphere containing only Cl or the industrial atmosphere containing only SO2. In addition, pH value is diverse in different coastal-industrial atmosphere. However, there are only few researches on the effect of pH value on the corrosion evolution of steels in the coastalindustrial atmosphere. Almost all the atmospheric corrosion data of steels were obtained by the field exposure test, which could not reflect the dependence of the atmospheric corrosion evolution of steels on pH value due to the difficulties in *国家自然科学基金项目 51201170和51131007,国家重点基础研究发展计划项目2014CB643300和国家材料环境腐蚀平台项目资助 收到初稿日期: 2014-07-23,收到修改稿日期: 2014-11-14 作者简介:陈文娟,女, 1986年生,博士生 DOI: 10.11900/0412.1961.2014.00407 第191-200页 pp.191-200

Numerical Approach for Atmospheric Corrosion Monitoring Based on EIS of a Weathering Steel

Electrochemical impedance spectroscopy (EIS) and film thickness measurement have been employed to study the atmospheric corrosion of a weathering steel covered with a thin electrolyte layer in a simulated coastal–industrial atmosphere. The results indicate that the corrosion rate is a function of the covered electrolyte thickness and the wet/dry cycle. Within each wet/dry cycle, the increased corrosion rate is related to the increased Cl− and SO4 2− concentration and an enhancement of oxygen diffusion rate with the evaporation of the electrolyte. In addition, the corrosion rate increases during the initial corrosion stage and then decreases as the wet/dry cycle proceeds. Moreover, one mathematical approach based on the numerical integration method to obtain corrosion mass loss of steel from the measurements of EIS has been developed, and this would be useful for the development of indoor simulated atmospheric corrosion tests.

EFFECT OF SO2 ON CORROSION EVOLUTION OF Q235B STEEL IN SIMULATED COASTAL-INDUSTRIAL ATMOSPHERE

The atmosphere in many cities along the coastal lines such as Qingdao in China has been polluted with SO2 due to the development of industry, and has been changed to coastal-industrial atmosphere. The corrosion behavior and mechanism of steel in coastal-industrial atmosphere with the co-existence of SO2 and Cl is different from that in the coastal atmosphere containing only Cl or the industrial atmosphere containing only SO2. It is necessary to study the corrosion mechanism of steel in the coastal-industrial atmosphere. However, almost all the atmospheric corrosion data of steels was obtained by the field exposure test, which could not reflect the dependence of SO2 or Cl on the atmospheric corrosion evolution of steels due to the difficulties in controlling the field conditions. So the effect of SO2 on the corrosion evolution of Q235B steel in the simulated coastal-industrial atmospheres was investigated by the dry/wet cyclic corrosion test (CCT), as well as XRD, electrochemical impedance spectroscopy (EIS) and polarization curve measurements. The results indicate that in the initial stage, the SO2 inhibits corrosion of Q235B steel. During the later stage, the corrosion rate of the steel increases with increasing the SO2 concentration to a certain level but further increasing the SO2 concentration contributes to a decreased corrosion rate. Besides, higher SO2 concentration can promote the formation of a-FeOOH while inhibit the formation of g-FeOOH and bFeOOH. Evolution of Q235B steel corrosion rate in the atmosphere with SO2 concentration is due to the *国家自然科学基金项目 51201170和 51131007资助 收到初稿日期: 2013-11-15,收到修改稿日期: 2014-03-13 作者简介:陈文娟,女, 1986年生,博士生 DOI: 10.3724/SP.J.1037.2013.00738

Effect of sulphur dioxide on the corrosion of a low alloy steel in simulated coastal industrial atmosphere

This investigation aims to study the effect of SO2 on the corrosion of a low alloy steel in simulated coastal industrial atmospheres. The results indicate that the corrosion weight gain of the steel firstly increases with increasing SO2 content to a certain level and then decreases with further increasing the SO2 content. Besides, higher SO2 content promotes the formation of α-FeOOH and inhibits the formation of γ-FeOOH. Moreover, it seems that the deterioration effect of SO2 to steel corrosion is not obvious in the initial corrosion stage and SO2 begins to accelerate the steel corrosion as the corrosion process increases.

Influence of RE Elements on Corrosion Rust Layer of Low Carbon Steel in CSP in Simulated Coastal Atmosphere

The influence of RE on corrosion rust layer of low carbon steel in CSP in a simulated coastal-industrial atmosphere was investigated by weight loss, SEM, XRD, and electrochemical measurements. The results demonstrate that the corrosion rate of low carbon steel in CSP with RE is higher at the initial stage and then lower in the late stage than that of samples without RE, which is caused by the formation of a compact and continuous rust layer with the addition of RE. The relative content of α-FeOOH and Fe3O4 in rust increased in the low carbon steel with RE indicates an improved protective ability of the rust. Using the analysis of resistance, the EIS results also indicate that the enhancement of protective ability of the rust layer by the RE is the main reason for increasing corrosion resistance of low carbon in CSP in simulated coastal atmosphere.

Evolution of atmospheric corrosion of MnCuP weathering steel in a simulated coastal-industrial atmosphere

The evolution of atmospheric corrosion of MnCuP weathering steel in a simulated coastal-industrial atmosphere was investigated by weight gain, SEM, XRD, and electrochemical measurements. The results indicate that the corrosion kinetics divides into two stages with a higher corrosion rate in the first stage and a lower rate in the second stage. The increased amount of α-FeOOH indicates an improved resistance of the rust. The rust enhances initially and then stabilizes the cathodic process, but the anodic process tends to be inhibited. The EIS results indicate that the protective ability of the rust layer can be evaluated by the charge transfer resistance.

Corrosion Behavior of New Weathering Steel in the Environment Simulating Coastal Industrial Atmosphere

The corrosion behavior of low carbon bainitic steel with Cu-P alloying in the environment simulating coastal industrial atmosphere was investigated by using dry-wet cycling corrosion test. 09CuPCrNi steel and low carbon bainitic steel without Cu-P alloying were used as comparative steels. The corrosion kinetics and electrochemical impedance spectra of the steels were measured, respectively. The morphologies of rust layers were observed by SEM and the phase constitutes of the rust layers were analyzed by XRD. Low carbon bainitic steel with Cu-P alloying behaves the lowest corrosion rate and the highest resistance of rust layer. Bainite microstructure is responsible for the uniform corrosion and the formation of dense rust layer. Cu-P alloying accelerates the transformation of gamma-FeOOH and Fe3O4 to thermodynamic stable phase alpha-FeOOH, which improves the protective effect of the rust layer.