Zhiwei Li, Dingding Li, Yulong Zhou, Haoping Peng, Aijun Xie and Jianhua Wang
This paper aims to contribute to the performance improvement and the broader application of hot-dip galvanized coating.
Abstract
Purpose
This paper aims to contribute to the performance improvement and the broader application of hot-dip galvanized coating.
Design/methodology/approach
First, the ability to provide barrier protection, galvanic protection, and corrosion product protection provided by hot-dip galvanized coating is introduced. Then, according to the varying Fe content, the growth process of each sublayer within the hot-dip galvanized coating, as well as their respective microstructures and physical properties, is presented. Finally, the electrochemical corrosion behaviors of the different sublayers are analyzed.
Findings
The hot-dip galvanized coating is composed of η-Zn sublayer, ζ-FeZn13 sublayer, δ-FeZn10 sublayer, and Γ-Fe3Zn10 sublayer. Among these sublayers, with the increase in Fe content, the corrosion potential moves in a noble direction.
Research limitations/implications
There is a lack of research on the corrosion behavior of each sublayer of hot-dip galvanized coating in different electrolytes.
Practical implications
It provides theoretical guidance for the microstructure control and performance improvement of hot-dip galvanized coatings.
Originality/value
The formation mechanism, coating properties, and corrosion behavior of different sublayers in hot-dip galvanized coating are expounded, which offers novel insights and directions for future research.
Details
Keywords
Jiaxin Li, Zhiyuan Zhu, Zhiwei Li, Yonggang Zhao, Yun Lei, Xuping Su, Changjun Wu and Haoping Peng
Gallic acid is a substance that is widely found in nature. Initially, it was only used as a corrosion inhibitor to retard the rate of corrosion of metals. In recent years, with…
Abstract
Purpose
Gallic acid is a substance that is widely found in nature. Initially, it was only used as a corrosion inhibitor to retard the rate of corrosion of metals. In recent years, with intensive research by scholars, the modification of coatings containing gallic acid has become a hot topic in the field of metal protection. This study aims to summarize the various preparation methods of gallic acid and its research progress in corrosion inhibitors and coatings, as well as related studies using quantum chemical methods to assess the predicted corrosion inhibition effects and to systematically describe the prospects and current status of gallic acid applications in the field of metal corrosion inhibition and protection.
Design/methodology/approach
First, the various methods of preparation of gallic acid in industry are understood. Second, the corrosion inhibition principles and research progress of gallic acid as a metal corrosion inhibitor are presented. Then, the corrosion inhibition principles and research progress of gallic acid involved in the synthesis and modification of various rust conversion coatings, nano-coatings and organic resin coatings are described. After that, studies related to the evaluation and prediction of gallic acid corrosion inhibition on metals by quantum chemical methods are presented. Finally, new research ideas on gallic acid in the field of corrosion inhibition and protection of metals are summarized.
Findings
Gallic acid can be used as a corrosion inhibitor or coating in metal protection.
Research limitations/implications
There is a lack of research on the synergistic improvement of gallic acid and other substances.
Practical implications
The specific application of gallic acid in the field of metal protection was summarized, and the future research focus was put forward.
Originality/value
To the best of the authors’ knowledge, this paper systematically expounds on the research progress of gallic acid in the field of metal protection for the first time and provides new ideas and directions for future research.
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Haoping Peng, Zhaolin Luan, Jun Liu, Yun Lei, Junxiu Chen, Song Deng and Xuping Su
This paper aims to under the laboratory environment, the corrosion behavior of X80 pipeline steel in oilfield injection water in eastern China was studied by immersion test.
Abstract
Purpose
This paper aims to under the laboratory environment, the corrosion behavior of X80 pipeline steel in oilfield injection water in eastern China was studied by immersion test.
Design/methodology/approach
First, the corrosion product film was immersed in oilfield injection water and the effect on the corrosion behavior and the corrosion reaction mechanism were constantly observed during this period. The effect was displayed by potentiodynamic polarization curve and electrochemical impedance spectrums (EIS) measurements. Second, scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction were used to observe and test the corrosion product film immersed in the oilfield water for 30 days.
Findings
The results indicate that the tendency of metal corrosion becomes weaker at an early stage, but strengthened later, which means the corrosion rate is accelerating. Besides, it is indicated by impedance spectroscopy that with the decreasing of the capacitance arc radius, the reaction resistance is reducing in this progress. Meanwhile, the character of Warburg impedance could be found in EIS, which means that the erosional components are more likely to penetrate the product film to reach the matrix. The corrosion product is mainly composed of the inner Fe3O4 layer and outer shell layer, which contains a large number of calcium carbonate granular deposits. It is this corrosion under fouling that produces severe localized corrosion, forming many etch pits on the metal substrate.
Originality/value
The experiment chose the X80 steel, the highest-grade pipeline steel used in China, to conduct the static immersion test in the injection water coming from an oilfield in eastern China. Accordingly, the corrosion mechanism and the effect of corrosion product film on the corrosion of pipeline steel were analyzed and discussed.
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The purpose of this paper is to explore the reasons for the high‐frequency switches of lead underwriters by Chinese listed companies in their seasoned equity offerings. It…
Abstract
Purpose
The purpose of this paper is to explore the reasons for the high‐frequency switches of lead underwriters by Chinese listed companies in their seasoned equity offerings. It contributes to the literature by filling the gap and providing evidence that institutional and non‐market factors could affect listed companies' decisions to switch their lead underwriters in the Chinese capital market.
Design/methodology/approach
This paper employs a numerical measure of listed companies' loyalty to evaluate their frequency of switching lead underwriters, and employs a Logit model and an OLS model to identify the key determinants of switching lead underwriters by Chinese listed companies.
Findings
It is observed that the frequency of switching lead underwriters is very high among Chinese listed companies for their seasoned offerings. It is also found that underwriters' deficient reputation and the lack of industrial experience, together with the depreciation of relationship‐specific assets, could have important impacts on lead underwriters being frequently switched in China. Besides, the frequent switches of lead underwriters could also be attributable to the non‐market supervision and regulatory influences by Chinese authorities over the security underwriting market.
Originality/value
This paper could help further the understanding of the factors that could explain the listed companies' frequent switches of their lead underwriters for their seasoned offerings in China. In addition, this paper has policy implications on how to improve the listed companies' loyalty for regulators in China. These implications could help improve the regulatory environment and promote the overall performance of the Chinese security underwriting market.