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1 – 10 of 60De Ding, Yue Zhang, Xiaobing Yu, Benling Fang, Jipu Guo, Jun Li, Lei Liu and Cuiwei Du
High-silicon cast iron has excellent corrosion resistance in some specific medium. But the effects of pH value, chloride concentration and soil moisture content on corrosion…
Abstract
Purpose
High-silicon cast iron has excellent corrosion resistance in some specific medium. But the effects of pH value, chloride concentration and soil moisture content on corrosion behavior are still unknown. This study aims to provide reference for the application of high-silicon cast iron in different environments.
Design/methodology/approach
Electrochemical impedance spectroscopy and potentiodynamic polarization curves were used to investigate the corrosion mechanism and rate. The morphology was observed by scanning electron microscopy. The chemical compositions of the corrosion products were detected by energy-dispersive spectroscopy and X-ray diffraction.
Findings
When the solution is acidic, the corrosion of high-silicon cast iron is more serious. When the chloride concentration is 0.1 per cent, the corrosion rate of high-silicon cast iron is the largest. A passive film is formed on the surface to prevent the corrosion reaction with the increasing of chloride concentration. The corrosion rate is the largest when water content is 15 per cent, and the corrosion is the lightest when water content is 30 per cent.
Originality/value
This study provides support for the selection of high-silicon cast iron as grounded material.
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Yue Zhang, Jun Xiao, Shaoguang Yang and Aimin Zhao
High silicon iron-based alloys possess excellent corrosion resistance in certain specific media, but the effects of electrolysis parameters on corrosion resistance remain unknown…
Abstract
Purpose
High silicon iron-based alloys possess excellent corrosion resistance in certain specific media, but the effects of electrolysis parameters on corrosion resistance remain unknown. This study aims to guide the development and application of an extra-low carbon high silicon iron-based alloy (ECHSIA) in electrode plates.
Design/methodology/approach
The corrosion resistance of ECHSIA and a conventional high-silicon cast iron (CHSCI) was analyzed through experimental characterizations. The morphology was observed by scanning electron microscopy. The influence of electrolysis parameters on the corrosion resistance of ECHSIA was investigated through corrosion experiments. The relationship between the electrolysis parameters and the corrosion resistance of ECHSIA was statistically investigated using the grey correlation analysis method.
Findings
The corrosion resistance of the ECHSIA is better than that of the CHSCI. The corrosion rate showed an increasing tendency with the increase in the nitric acid concentration (CHNO3), electrolyte temperature and current density. The grey correlation analysis results showed that the CHNO3 was the main factor affecting the corrosion rate of the ECHSIA.
Originality/value
An ECHSIA with a single ferrite microstructure was prepared. This study provides a guideline for the future development and application of ECHSIAs as electrode plates.
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Kechen Lv, Xinyu Yang, Tangqing Wu, Song Xu, Lanlan Liu, Lin Sun and Xinming Wang
High-silicon chromium iron (HSCI) has been used in ground grids in southern China, while there was a lack of study on its corrosion behavior in this soil environment. The purpose…
Abstract
Purpose
High-silicon chromium iron (HSCI) has been used in ground grids in southern China, while there was a lack of study on its corrosion behavior in this soil environment. The purpose of this paper is to discover the corrosion of HSCI in acidic and alkaline soil solutions.
Design/methodology/approach
The original defects on the HSCI surface were observed using optical microscopy, and the corrosion behavior of the HSCI in the acidic and alkaline soil solutions were jointly detected using electrochemical measurements and scanning electron microscopy/energy dispersive spectrometer.
Findings
The results showed the corrosion rates of the HSCI in the acidic and alkaline soil solutions were limited, and the high contents of Cr and Si in matrix was responsible for its high corrosion resistance. The HSCI showed a similar corrosion tendency in the two solutions, while its corrosion rate in the acid soil solution was higher than that in the alkaline soil solution. The corrosion pits on the specimen surface were originated from the original defects in matrix, and the edges of the corrosion pits were more rounded than the original defects after 720 h immersion in the two solutions. The original defects in the HSCI matrix played a significant role in the corrosion process.
Originality/value
The paper discovered the corrosion evolution of HSCI in the acidic and alkaline soil solutions. What is more, the acceleration role of the original defects on the corrosion of the HSCI in the acidic and alkaline soil solutions was discovered in the paper. The results are beneficial for the material selection of ground grid equipment in engineering.
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The U.S. National Bureau of Standards has carried out investigations on the corrosion of metals in soils over a period of 45 years. This basic research work has recently been…
Abstract
The U.S. National Bureau of Standards has carried out investigations on the corrosion of metals in soils over a period of 45 years. This basic research work has recently been published in a special report of the Bureau—the most thorough and elaborate one of its kind ever attempted—aiming to provide a highly useful reference material for the technician who is interested or involved in the theoretical and mechanical aspects of the problem. The report has been written and summarised by Melvin Romanoff. This article is a summary of that section of the report dealing with the results of the Bureau's study of the effect of soils free of stray currents on commonly used pipe materials.
Ayomide Osundare, Daniel Toyin Oloruntoba and Patricia Popoola
The purpose of this paper is to develop technically efficient and economically effective sacrificial anodes that can be used for cathodic protection (CP) of pipelines in marine…
Abstract
Purpose
The purpose of this paper is to develop technically efficient and economically effective sacrificial anodes that can be used for cathodic protection (CP) of pipelines in marine environment and fill the knowledge gap in the use of carbon anodes for CP.
Design/methodology/approach
A sacrificial anode was produced via sand casting by adding varying weight-percent of coal and ferrosilicon to a constant weight-percent of grey cast iron. The hardness of the produced anodes was evaluated using a Rockwell hardness tester. The microstructure of the anodes was observed with scanning electron microscope/energy-dispersive spectroscopy (SEM/EDS). X-ray diffraction (XRD) was used to study the phases present. A potentiostat was used to assess the corrosion behaviour of the produced anodes and mild steel in 3.5 Wt.% NaCl solution.
Findings
The SEM results showed that some anodes had interdendritic graphite formation, while others had pronounced graphite flakes. The EDS analysis showed carbon and iron to be the prominent elements in the anode. Anodes Bc, B2 and B5 with a corrosion rate of two order of magnitudes were observed to have similar dendritic structures. Anode B4 is the most electronegative with an Ecorr of −670.274 mV Ag/AgCl and a corrosion rate of 0.052475 mmpy. The produced anodes can be used to protect mild steel in the same environment owing to their lower Ecorr values compared to that of mild steel −540.907 mV Ag/AgCl.
Originality/value
Alloying has been majorly used to improve the efficiency of sacrificial anodes and to alleviate its setbacks. However, development of more technically efficient and economically effective sacrificial anodes via production of composite has not been exhaustively considered. Hence, this research focuses on the development of a carbon based anode by adding natural occurring coal and ferrosilicon to grey cast iron. The corrosion behaviour of the produced anode was evaluated and compared to that of mild steel in marine environment.
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In the manufacture of ammonium sulphate, whether by using evaporators or saturators, the erosive effect of crystals present in solution, the low sulphuric acid concentrations…
Abstract
In the manufacture of ammonium sulphate, whether by using evaporators or saturators, the erosive effect of crystals present in solution, the low sulphuric acid concentrations usually present, and the relatively high temperatures of operation give rise to serious corrosion problems which begin at the drawing board stage of design and continue through all stages of manufacture. These corrosion problems are discussed in detail in this article and advice is given on materials of construction, including stainless steels, nickel alloys, rubber‐lined mild steel, lead, silicon irons, aluminium and a number of plastics.
Background An increasing number of requests from the engineering industry are being received by the author's company to advise on procedures for modern anti‐corrosive treatment…
Abstract
Background An increasing number of requests from the engineering industry are being received by the author's company to advise on procedures for modern anti‐corrosive treatment and protection of valves, pumps, compressors, heat exchangers, filters etc.
Zhenxing Ren, Daowu Yang, Jun Liu, Yong Ma, Zhongtang Huo and Shaochang Zheng
The purpose of the paper was to design an anti-corrosion system that combined conductive coatings with cathodic protection for a 500-kV substation ground grid, and provide a basis…
Abstract
Purpose
The purpose of the paper was to design an anti-corrosion system that combined conductive coatings with cathodic protection for a 500-kV substation ground grid, and provide a basis for the anti-corrosion construction of the installation.
Design/methodology/approach
The study took the Shaoguan 500-kV substation grounding grid as the research object. The anti-corrosion performance of KV conductive coatings on grounding metal was researched. In parallel, the alkalinity of substation soil was evaluated according to the German DIN50929 Standard, and the combined protection system comprising conductive coatings and impressed current cathodic protection was designed.
Findings
KV conductive coatings, that have resistance to acids, alkalis and salts, can effectively slow down the corrosion rate of the grounding grid. The investigation also provided the outline design, installation, construction requirements and monitoring methods for the 500-kV substation grounding grid.
Originality/value
This report contains some guiding significance for anti-corrosion engineering of 500-kV substation grounding grids.
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W. Shepherd and CEng
There is a paramount need in process plant for effective control of corrosion. Corrosion can contaminate the product handled, cause unsafe conditions to develop or cause pollution…
Abstract
There is a paramount need in process plant for effective control of corrosion. Corrosion can contaminate the product handled, cause unsafe conditions to develop or cause pollution if a vessel or pipeline leaks or collapses. Viewed in a positive light, efficient corrosion prevention can lead to economic plant life, a reduction in downtime for plant replacement, a good product and a safer working environment.
Summary This paper examines the function, protection and applications of complex components such as valves in off‐shore environments. Materials of Construction and the…
Abstract
Summary This paper examines the function, protection and applications of complex components such as valves in off‐shore environments. Materials of Construction and the coating/lining techniques and procedures available to ensure acceptable function and protection are discussed, while the limitations of existing painting specifications from the point of view of the component manufacturer are emphasised. Off‐shore services utilising valves are summarised and the types of valves to be found in service on production platforms are indicated.