Influence of steel composition on the mechanical properties and Zn-Mg-Al coating layer on the corrosion resistance of steel wire ropes for offshore applications

Steel rope is generally used for mooring application. Recently, higher strength and corrosion resistance are required to avoid the weight penalty with increase of the sea-water depth in offshore oil production. This can be achieved by increasing the carbon content and adding alloy elements in zinc c...

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Main Author:	Myung, Hyun Cho
Format:	Thesis
Language:	English
Published:	2016
Subjects:	TJ Mechanical engineering and machinery
Online Access:	http://eprints.utm.my/id/eprint/78811/1/MyungHyunChoPFKM2016.pdf
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spelling	my-utm-ep.788112018-09-17T04:13:06Z Influence of steel composition on the mechanical properties and Zn-Mg-Al coating layer on the corrosion resistance of steel wire ropes for offshore applications 2016-06 Myung, Hyun Cho TJ Mechanical engineering and machinery Steel rope is generally used for mooring application. Recently, higher strength and corrosion resistance are required to avoid the weight penalty with increase of the sea-water depth in offshore oil production. This can be achieved by increasing the carbon content and adding alloy elements in zinc coating. Three objectives of the research were conducted as follows; to investigate the effect of composition on strength and corrosion resistance of galvanized wire, to investigate the degradation mechanism of high tensile strength (2,150 ~2,250MPa) galvanized steel rope in sea-water and to develop a Zn-Al-Mg ternary alloy coating to enhance the corrosion resistance of steel ropes. Microstructural characterisation on coated steel wires was carried out using optical microscope, field emission scanning electron microscope (FESEM) equipped with energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD). Both Tafel polarization and salt spray tests were conducted to investigate the corrosion resistance of Zn-Mg-Al alloy coatings. Torsion, fatigue and tensile tests were conducted. The best fatigue property was obtained at 2,167MPa tensile strength. Tensile strength above 2,167MPa, fatigue and torsion properties were reduced and the susceptibility to surface defect also was increased during fatigue testing, by which cracks can be easily created and grown at different planes at the same time. It is the main cause of fatigue degradation. Degradation of mooring rope is caused by combination of fretting and corrosion which normally occurs in wire rope assembly type known as Independent Wire Rope Core (IWRC). Excellent corrosion resistance over 3,000 hours based on salt spray test was obtained by addition of magnesium and aluminium elements in the range of 1.0~3.0wt% but no improvement for over 3wt% Mg, which might be attributed to coarsening of the phase grains. The multi-layer coatings in which each layer consists of several different alloy phases has an advantage because each phase has a unique function and they exert their synergic functions in corrosion environment. As a conclusion, applying Zn-Mg-Al coating to mooring rope improves life span of rope due to reduced crack in the coating and excellent corrosion resistance. 2016-06 Thesis http://eprints.utm.my/id/eprint/78811/ http://eprints.utm.my/id/eprint/78811/1/MyungHyunChoPFKM2016.pdf application/pdf en public http://dms.library.utm.my:8080/vital/access/manager/Repository/vital:106019 phd doctoral Universiti Teknologi Malaysia, Faculty of Mechanical Engineering Faculty of Mechanical Engineering
institution	Universiti Teknologi Malaysia
collection	UTM Institutional Repository
language	English
topic	TJ Mechanical engineering and machinery
spellingShingle	TJ Mechanical engineering and machinery Myung, Hyun Cho Influence of steel composition on the mechanical properties and Zn-Mg-Al coating layer on the corrosion resistance of steel wire ropes for offshore applications
description	Steel rope is generally used for mooring application. Recently, higher strength and corrosion resistance are required to avoid the weight penalty with increase of the sea-water depth in offshore oil production. This can be achieved by increasing the carbon content and adding alloy elements in zinc coating. Three objectives of the research were conducted as follows; to investigate the effect of composition on strength and corrosion resistance of galvanized wire, to investigate the degradation mechanism of high tensile strength (2,150 ~2,250MPa) galvanized steel rope in sea-water and to develop a Zn-Al-Mg ternary alloy coating to enhance the corrosion resistance of steel ropes. Microstructural characterisation on coated steel wires was carried out using optical microscope, field emission scanning electron microscope (FESEM) equipped with energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD). Both Tafel polarization and salt spray tests were conducted to investigate the corrosion resistance of Zn-Mg-Al alloy coatings. Torsion, fatigue and tensile tests were conducted. The best fatigue property was obtained at 2,167MPa tensile strength. Tensile strength above 2,167MPa, fatigue and torsion properties were reduced and the susceptibility to surface defect also was increased during fatigue testing, by which cracks can be easily created and grown at different planes at the same time. It is the main cause of fatigue degradation. Degradation of mooring rope is caused by combination of fretting and corrosion which normally occurs in wire rope assembly type known as Independent Wire Rope Core (IWRC). Excellent corrosion resistance over 3,000 hours based on salt spray test was obtained by addition of magnesium and aluminium elements in the range of 1.0~3.0wt% but no improvement for over 3wt% Mg, which might be attributed to coarsening of the phase grains. The multi-layer coatings in which each layer consists of several different alloy phases has an advantage because each phase has a unique function and they exert their synergic functions in corrosion environment. As a conclusion, applying Zn-Mg-Al coating to mooring rope improves life span of rope due to reduced crack in the coating and excellent corrosion resistance.
format	Thesis
qualification_name	Doctor of Philosophy (PhD.)
qualification_level	Doctorate
author	Myung, Hyun Cho
author_facet	Myung, Hyun Cho
author_sort	Myung, Hyun Cho
title	Influence of steel composition on the mechanical properties and Zn-Mg-Al coating layer on the corrosion resistance of steel wire ropes for offshore applications
title_short	Influence of steel composition on the mechanical properties and Zn-Mg-Al coating layer on the corrosion resistance of steel wire ropes for offshore applications
title_full	Influence of steel composition on the mechanical properties and Zn-Mg-Al coating layer on the corrosion resistance of steel wire ropes for offshore applications
title_fullStr	Influence of steel composition on the mechanical properties and Zn-Mg-Al coating layer on the corrosion resistance of steel wire ropes for offshore applications
title_full_unstemmed	Influence of steel composition on the mechanical properties and Zn-Mg-Al coating layer on the corrosion resistance of steel wire ropes for offshore applications
title_sort	influence of steel composition on the mechanical properties and zn-mg-al coating layer on the corrosion resistance of steel wire ropes for offshore applications
granting_institution	Universiti Teknologi Malaysia, Faculty of Mechanical Engineering
granting_department	Faculty of Mechanical Engineering
publishDate	2016
url	http://eprints.utm.my/id/eprint/78811/1/MyungHyunChoPFKM2016.pdf
_version_	1747818077072916480

Influence of steel composition on the mechanical properties and Zn-Mg-Al coating layer on the corrosion resistance of steel wire ropes for offshore applications

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