Please wait a minute...
Acta Metall Sin  2018, Vol. 54 Issue (4): 527-536    DOI: 10.11900/0412.1961.2017.00149
Orginal Article Current Issue | Archive | Adv Search |
Investigation of Corrosion Behavior of Welded Joint of X70 Pipeline Steel for Deep Sea
Ge MA, Xiurong ZUO(), Liang HONG, Yinglun JI, Junyuan DONG, Huihui WANG
Key Laboratory of Material Physics, Ministry of Education, Zhengzhou University, Zhengzhou 450052, China
Download:  HTML  PDF(6540KB) 
Export:  BibTeX | EndNote (RIS)      

X70 pipeline steel with thick specifications (40.5 mm) for 3500 m deep sea reached the international advanced level in the wall thickness and service depth. Due to the high heat input during the welding process, the corrosion resistance of inside welding and outside welding would vary depending on the microstructure differences. The corrosion resistance of the welded joints of X70 pipeline for deep sea was studied by the immersion test, the weight loss test, the electrochemical test in this work. The components of the passive film were analyzed by XRD and the microstructure was observed by SEM. The results show that the corrosion resistance of the weld metal is the best. The corrosion resistance of the heat affected zone follows. The corrosion resistance of the base metal is the worst. And for the same area, the corrosion resistance of the inside welding is better than that of the outside welding. The formation of dense Fe3O4 passivation film can effectively slow down the progress of the reaction, and the corrosion products of Fe2O3, FeOOH and Fe(OH)3 which are loose in the outer layer, have no protective effect on the matrix. The microstructure of the weld metal with the best corrosion resistance is mostly the intragranular nucleation ferrite and martensite-austenite (M-A) constituent is fine and uniform. The microstructure gradient of the heat affected zone is the largest, the M-A constituent is coarse and the corrosion resistance is inferior to the weld metal. The base metal consists of ferrite and bainite, the bainite is island-like distribution and the corrosion resistance is the worst. Microstructure of the inside welding is more refined, owing to the influence of outside welding thermal cycle, and the volume fraction of M-A constituent in inside welding is higher than that of the outside welding, so the corrosion resistance is better than that of the outside welding.

Key words:  X70 pipeline      pitting      inclusion      microstructure      M-A constituent     
Received:  25 April 2017     
ZTFLH:  TG172.6  

Cite this article: 

Ge MA, Xiurong ZUO, Liang HONG, Yinglun JI, Junyuan DONG, Huihui WANG. Investigation of Corrosion Behavior of Welded Joint of X70 Pipeline Steel for Deep Sea. Acta Metall Sin, 2018, 54(4): 527-536.

URL:     OR

Fig.1  Diagram (a) and macroscopic morphology (b) of X70 pipeline steel (BM—base metal, HAZ—heat affected zone, WM—weld metal, WMin—inside weld metal, HAZin—inside heat affected zone, BMin—inside base metal, WMout—outside weld metal, HAZout—outside heat affected zone, BMout—outside base metal)
Position C Mn P S Si Ni+Cr+Cu+Mo Nb+Ti Fe
Base metal 0.044 1.56 0.009 0.009 0.25 0.475 0.069 Bal.
Weld metal 0.074 1.54 0.011 0.002 0.28 0.691 0.043 Bal.
Table 1  Chemical compositions of base metal and weld metal in X70 pipeline steel (mass fraction / %)
Fig.2  Macro morphologies of welded joints after immersion 2 h in 3.5%NaCl solution

(a) untreated (b) polished

Fig.3  OM images of welded joints after immersion 2 h in 3.5%NaCl solution (d—diameter)

(a) WMin (b) HAZin (c) BMin (d) WMout (e) HAZout (f) BMout

Fig.4  Statistical results of pitting corrosion of welded joints after immersion 2 h in 3.5%NaCl solution

(a) number of pits per unit area (b) proportion of pits in a certain diameter range

Fig.5  Results of weight loss test of welded joints in 3.5%NaCl solution

(a) average mass change curve (b) average corrosion rate curve

Fig.6  XRD spectra of passive film of welded joints after immersion 96 h in 3.5%NaCl solution
Fig.7  Open circuit potentials of each region of welded joints
Fig.8  Potentiodynamic polarization curves in each region of welded joints (E—potential, i—current density)

(a) outside welding (b) inside welding

Position Ecorr / mV icorr / (mAcm-2)
BMout -691 1.340×10-4
HAZout -689 2.608×10-4
WMout -680 6.934×10-5
BMin -648 6.644×10-4
HAZin -609 6.996×10-4
WMin -583 4.919×10-4
Table 2  Self corrosion potential (Ecorr) and self corrosion current density (icorr) in different regions of welded joints
Fig.9  Different morphologies (a, b) and corresponding EDS analyses (c, d) of oxide inclusions of Ti (a, c) and composite oxide inclusions (b, d) in welded joints after immersion 96 h in 3.5%NaCl solution
Fig.10  SEM images of welded joints in different regions (AF—acicular ferrite, LB—lath bainite, GB—granular bainite, PF—polygonal ferrite, M-A—martensite-austenite)

(a) WM (b) coarse grain heat affected zone (CGHAZ) (c) fine grain HAZ (FGHAZ) (d) intercritical HAZ (ICHAZ) (e) BM

Fig.11  OM images of M-A constituents in each area of the outside welding

(a) WM (b) CGHAZ (c) FGHAZ (d) IGHAZ (e) BM

Fig.12  M-A constituent size distributions of per unit area of welded joints

(a) outside welding (b) inside welding

[1] Li S S, Liu M, Zuo X R, et al.Prospect of development and application of pipeline steel for deep water[J]. Hot Work. Technol., 2013, 42(18): 23(李树森, 刘敏, 左秀荣等. 深海管线用钢开发及应用前景[J]. 热加工工艺, 2013, 42(18): 23)
[2] Rihan R O.Galvanic corrosion of electric resistance welded X52 steel in CO2-containing solution[J]. Anti-Corros. Method. Mater., 2014, 61: 431
[3] Zhao W, Zou Y, Matsuda K, et al.Corrosion behavior of reheated CGHAZ of X80 pipeline steel in H2S-containing environments[J]. Mater. Des., 2016, 99: 44
[4] Alizadeh M, Bordbar S.The influence of microstructure on the protective properties of the corrosion product layer generated on the welded API X70 steel in chloride solution[J]. Corros. Sci., 2013, 70: 170
[5] Huang M, Zhang M X, Wang Y, et al.Electrochemical behaviour of X80 pipeline steel with alumina coating[J]. Surf. Eng., 2015, 31: 295
[6] Kuang D, Cheng Y F.Study of cathodic protection shielding under coating disbondment on pipelines[J]. Corros. Sci., 2015, 99: 249
[7] Zhao P X, Zuo X R, Chen K, et al.Corrosion behavior of X80 pipeline steel with strain-based design[J]. Trans. Mater. Heat Treat., 2013, 34(suppl.2): 221(赵鹏翔, 左秀荣, 陈康等. X80大变形管线钢的腐蚀行为[J]. 材料热处理学报, 2013, 34(增刊 2): 221)
[8] Wang Y P, Zuo X R, Li J L.Corrosion resistance of the welded joint of submarine pipeline steel with ferrite plus bainite dual-phase microstructure[J]. Steel Res. Int., 2015, 86: 1260
[9] Cai G J, Li C S.Effects of Ce on inclusions and corrosion resistance of low-nickel austenite stainless steel[J]. Mater. Corros., 2015, 66: 1445
[10] Liu C, Guo Y B, Wang D G, et al.Effects of alternating stray current on corrosion behavior of X80 pipeline steel[J]. Corros. Prot., 2015, 36: 213(刘骋, 郭岩宝, 王德国等. 交流杂散电流对X80管线钢腐蚀行为的影响[J]. 腐蚀与防护, 2015, 36: 213)
[11] Xie Y, Li Y, Sun T, et al.Study on the protection of Q235 steel by in situ grown pure γ-FeOOH and α-FeOOH rust film[J]. Chin. Sci. Bull., 2008, 53: 2848(谢颖, 李瑛, 孙挺等. 原位生长的纯γ-FeOOH和α-FeOOH锈膜对Q235钢保护性能的研究[J]. 科学通报, 2008, 53: 2848)
[12] Zhu J Y, Xu L N, Feng Z C, et al.Galvanic corrosion of a welded joint in 3Cr low alloy pipeline steel[J]. Corros. Sci., 2016, 111: 391
[13] Shim J H, Cho Y W, Chung S H, et al.Nucleation of intragranular ferrite at Ti2O3 particle in low carbon steel[J]. Acta Mater., 1999, 47: 2751
[14] Grigorovich K V, Shibaeva T V, Arsenkin A M.Effect of a pipe-steel killing technology on the composition and number of nonmetallic inclusions[J]. Russ. Metall., 2011, 2011: 927
[15] Zheng S Q, Chen C F, Chen L Q.Influence of S contents on the hydrogen blistering and hydrogen induced cracking of A350LF2 steel[J]. Mater. Sci. Appl., 2011, 2: 917
[16] Cheng Y Y, Chen Z Z, Niu Y J, et al. Influence of inclusions on strength and toughness of X70 pipeline steel Girth Weld [J]. Appl. Mech. Mater., 2012, 182-183: 1554
[17] Lang F J, Huang X Q, Pang T, et al. Effect of inclusion on pitting corrosion of X80 pipeline steel [J]. Adv. Mater. Res., 2015, 1120-1121: 999
[18] Wang J Q, Atrens A, Cousens D R, et al.Measurement of grain boundary composition for X52 pipeline steel[J]. Acta Mater., 1998, 46: 5677
[19] Zhu Z X, Kuzmikova L, Li H J, et al.Effect of inter-critically reheating temperature on microstructure and properties of simulated inter-critically reheated coarse grained heat affected zone in X70 steel[J]. Mater. Sci. Eng., 2014, A605: 8
[20] Alé R M, Rebello J M A, Charlier J. A metallographic technique for detecting martensite-austenite constituents in the weld heat-affected zone of a micro-alloyed steel[J]. Mater. Charact., 1996, 37: 89
[21] Hrivnak I, Matsuda F, Li Z L, et al.Investigation of metallography and behavior of M-A constituent in Weld HAZ of HSLA steels (Materials, Metallurgy & Weldability)[J]. Trans. JWRI, 1992, 21: 241
[22] Pardal J M, da Silva M R, Bastos I N, et al. Influence of tempering treatment on microstructure and pitting corrosion resistance of a new super ferritic-martensitic-austenitic stainless steels with 17%Cr[J]. Corros. Eng., Sci. Technol., 2016, 51: 337
[23] Wang L W, Du C W, Liu Z Y, et al.Influence of carbon on stress corrosion cracking of high strength pipeline steel[J]. Corros. Sci., 2013, 76: 486
[24] Masumoto T.Studies on electrolytic extraction of carbides in iron and steels[J]. Tetsu Hagané, 1969, 55: 1347(増本健. 鉄鋼中の炭化物の電解抽出条件の検討[J]. 鉄と鋼, 1969, 55: 1347)
[25] Tsai W T, Chen J R.Galvanic corrosion between the constituent phases in duplex stainless steel[J]. Corros. Sci., 2007, 49: 3659
[1] JIANG He,DONG Jianxin,ZHANG Maicang,YAO Zhihao,YANG Jing. Stress Relaxation Mechanism for Typical Nickel-Based Superalloys Under Service Condition[J]. 金属学报, 2019, 55(9): 1211-1220.
[2] ZHANG Beijiang,HUANG Shuo,ZHANG Wenyun,TIAN Qiang,CHEN Shifu. Recent Development of Nickel-Based Disc Alloys andCorresponding Cast-Wrought Processing Techniques[J]. 金属学报, 2019, 55(9): 1095-1114.
[3] Jinyao MA,Jin WANG,Yunsong ZHAO,Jian ZHANG,Yuefei ZHANG,Jixue LI,Ze ZHANG. Investigation of In Situ 1150 High Temperature Deformation Behavior and Fracture Mechanism of a Second Generation Single Crystal Superalloy[J]. 金属学报, 2019, 55(8): 987-996.
[4] Sensen HUANG,Yingjie MA,Shilin ZHANG,Min QI,Jiafeng LEI,Yaping ZONG,Rui YANG. Influence of Alloying Elements Partitioning Behaviors on the Microstructure and Mechanical Propertiesin α+β Titanium Alloy[J]. 金属学报, 2019, 55(6): 741-750.
[5] Qiaomu LIU,Shunzhou HUANG,Fang LIU,Yan YANG,Hongqiang NAN,Dong ZHANG,Wenru SUN. Effect of Boron Content on Microstructure Evolution During Solidification and Mechanical Properties of K417G Alloy[J]. 金属学报, 2019, 55(6): 720-728.
[6] Chunbo LAN,Jianeng LIANG,Yuanxia LAO,Dengfeng TAN,Chunyan HUANG,Xianzhong MO,Jinying PANG. Anomalous Thermal Expansion Behavior of Cold-RolledTi-35Nb-2Zr-0.3O Alloy[J]. 金属学报, 2019, 55(6): 701-708.
[7] Zheng LIU,Jianrong LIU,Zibo ZHAO,Lei WANG,Qingjiang WANG,Rui YANG. Microstructure and Tensile Property of TC4 Alloy Produced via Electron Beam Rapid Manufacturing[J]. 金属学报, 2019, 55(6): 692-700.
[8] Jianxiang DING,Wubian TIAN,Dandan WANG,Peigen ZHANG,Jian CHEN,Zhengming SUN. Arc Erosion and Degradation Mechanism ofAg/Ti2AlC Composite[J]. 金属学报, 2019, 55(5): 627-637.
[9] Tongbang AN,Jinshan WEI,Jiguo SHAN,Zhiling TIAN. Influence of Shielding Gas Composition on Microstructure Characteristics of 1000 MPa Grade Deposited Metals[J]. 金属学报, 2019, 55(5): 575-584.
[10] Ping LI, Quan LIN, Yufeng ZHOU, Kemin XUE, Yucheng WU. TEM Analysis of Microstructure Evolution Process of Pure Tungsten Under High Pressure Torsion[J]. 金属学报, 2019, 55(4): 521-528.
[11] Dechun REN, Huhu SU, Huibo ZHANG, Jian WANG, Wei JIN, Rui YANG. Effect of Cold Rotary-Swaging Deformation on Microstructure and Tensile Properties of TB9 Titanium Alloy[J]. 金属学报, 2019, 55(4): 480-488.
[12] Kaiqiang LI, Lujia YANG, Yunze XU, Xiaona WANG, Yi HUANG. Influence of SO42- on the Corrosion Behavior of Q235B Steel Bar in Simulated Pore Solution[J]. 金属学报, 2019, 55(4): 457-468.
[13] Yaohong LIU,Zhaohui WANG,Ke LIU,Shubo LI,Wenbo DU. Effects of Er on Hot Cracking Susceptibility of Mg-5Zn-xEr Magnesium Alloys[J]. 金属学报, 2019, 55(3): 389-398.
[14] Zhaozhao Lü,Yufei ZU,Jianjun SHA,Yuqiang XIAN,Wei ZHANG,Ding CUI,Conglin YAN. Fabrication and Mechanical Properties of Carbon Fiber-Reinforced Aluminum Matrix Compositeswith Cu Interphase[J]. 金属学报, 2019, 55(3): 317-324.
[15] Chengwei SHAO, Weijun HUI, Yongjian ZHANG, Xiaoli ZHAO, Yuqing WENG. Microstructure and Mechanical Properties of a Novel Cold Rolled Medium-Mn Steel with Superior Strength and Ductility[J]. 金属学报, 2019, 55(2): 191-201.
[1] . [J]. Acta Metall Sin, 2000, 36(12): 1240 -1243 .
[2] . Effects of Al2O3 and Cr Interlayers on the Optical Property and Adhesion of Ag Film[J]. Acta Metall Sin, 2007, 43(3): 307 -310 .
[3] Yuan Liu. Fabrication of Regular Porous Magnesium with Radial Pore Distribution[J]. Acta Metall Sin, 2006, 42(10): 1075 -1080 .
[5] WANG Weimin; BIAN Xiufang ;QIN Jingyu(College of Meterial Science and Technology Shandong University of Technology Jinan 250061)S.LSliusarenko(Institute of metal physics ; Ukraine Academy of Science; Kiev-142; 252142; Ukraine)Correspondent : WANC Weimin; E-mail.. weiminw dms sudt edu cn. THE COVALENT BOND IN LIQUID Al-Si ALLOY AND EFFECT OF Sr ON THE BOND[J]. Acta Metall Sin, 1998, 34(6): 645 -649 .
[6] ZHANG Ji;ZHANG Zhihong;ZOU Dunxu;ZHONG Zengyong(Central Iron and Steel Research Institute;Ministry of Metallurgical Industry;Beijing 100081)(Manuscript received 1995-12-25)(Department 5;Central Iron and Steel Research Institute;MMI;BeiJing 100081). FRACTURE MECHANISMS OF FFL MICROSTRUCTURE IN TiAl ALLOY[J]. Acta Metall Sin, 1996, 32(10): 1044 -1048 .
[7] FAN Yunchang; JIA NG Zhiqing (Shijiazhuang Railway institute;Shijiazhuang 050043)(Manuscript received 1995-03-30; in revised form 1995-05-29). HYDROGEN EMBRITTLEMENT OF SPHEROIDIZED HIGH CARBON STEEL SHEET UNDER MULTIAXIAL STRESS STATE[J]. Acta Metall Sin, 1995, 31(10): 445 -454 .
[8] MENG Changgong;GUO Jianting;HU Zhuangqi Institute of Metal Research; Academia Sinica; Shenyang. MECHANISM FOR DUCTILIZATION OF Ni_3Al WITH Pd-DOPING[J]. Acta Metall Sin, 1993, 29(11): 28 -32 .
[9] HONG Yanruo(Y.R.Hong);Professor;Gruduate School; Beijing University of Iron and Steel Technology. STUDY ON γ/γ+NbC_x PHASE BOUNDARY IN Fe-Nb-C SYSTEM[J]. Acta Metall Sin, 1988, 24(1): 114 -118 .
[10] ZHOU Jicheng (Shanghai Institute of Metallurgy; Academia Sinica); TIAN Yahwen; MA Yonghui; ZHU Limin (North-East Institute of Technology; Shenyang);. DISTRIBUTION OF Al AND Ce BETWEEN Ag AND Fe[J]. Acta Metall Sin, 1986, 22(5): 78 -84 .