44 1 Vol.44 No.1 8 1 149 1444 ACTA METALLURGICA SINICA Dec. 8 pp.149 1444 X7 µ CO ß ¹Ü ½ ¼»º ¾ («ÓËÐ ÅËË, «ÛÓÜ»«ÛÐ, «18) ³ ± Ó ¼ÄÞ ÏÑ ÀÔ Ë Ü (SSRT) ± CO Ý X7 Æ ¾ĐÄ Ì Î ¼ (SCC) ¹ É, Ê ÄÞ CO Ó ÛÜ Ö. Ð: CO ½ FeCO, Ͻ Fe Ñ Fe(CO ), Û X7 Æ ; CO H O ½ H CO À HCO, ¹ ¹ H. X7 Æ ¾ CO Ì SCC ǹ Ã Þ Ç, µ CO Ó Û, ÃÓ Ì. Û Æ, CO, Î ¼, ÐĐÆ TG17.7 Ø A 411961(8)11496 CORROSION BEHAVIOR OF X7 PIPELINE STEEL IN SIMULATED KU ERLE SOIL SOLUTION WITH CO ZHANG Liang, LI Xiaogang, DU Cuiwei, LIU Zhiyong, LIANG Ping Corrosion and Protection Center, University of Science and Technology Beijing, and Key Lab of Corrosion, Erosion and Surface Technique Beijing, Beijing 18 Correspondent: ZHANG Liang, Tel: (1)691, E-mail: zhl 815@sina.com.cn Supported by National Science and Technology Infrastructure Platforms Construction Projects (No.5DKA14) and Major Fund of National Tenth Five Project (No.5499 8) Manuscript received 8 1, in revised form 8 9 1 ABSTRACT The effect of CO on the stress corrosion cracking (SCC) behavior of X7 pipeline steel in simulated Ku erle soil solution was investigated by polarization curve, EIS and slow strain rate testing (SSRT). The morphologies of fracture surface of X7 pipeline steel in the solution with the different partial pressures of CO were analyzed by SEM. The results show that the dissolved CO reacted with the corrosion product of FeCO and a dissolved complex (Fe(CO ) ) is formed. The cathodic regime representing evolution of hydrogen is also affected by the presence of dissolved CO. The SCC of X7 pipeline steel in dissolved CO solution follows the mechanism of hydrogen facilitated dissolution. As the increase of the pressure of CO in the solution, the effect of hydrogen induced cracking is enhanced. KEY WORDS pipeline steel, CO, stress corrosion cracking, cathode reaction Û Ï ½ (stress corrosion cracking, SCC) Ï Æ, ÏÁ Ê» Ô ¹ Ï Á Ï,, ½ ÙÅ, º À» [14]. CO Æ¾Ü Ç, Á ± Ö. º Ð, CO Æ Ý Á, [5]. Þ Ð CO Ï È [6,7], ÈÈÐ ß ÌÔ, * Ú Ô Æ ÊË 5DKA14 À Ú Ì Ë 5499-8 Ô ± : 8 1, Ô ± : 8 9 1 Ó :, Å, 198 Ï, Ï CO ± ph Á, ÅÐ CO ÆÔ±. CO Þ SCC Ô È º [815]. Ø Á ± Đ² X7 Ç. Ç Å Õ, ß, Õ Å [16]. ÇÓ ÅÍ, ͵ Å Ð Â ¹ CO ( ½² CO ), Ç «Ï. Æ Ø² X7 Ç ½ Ï Đ. ² Å Å º, Ç, Ø ² X7 Ç CO ÆÔ Å Í º Ï ½ ÁÜ È. 1 ² Ý º ¹ X7 Ç, Ò¾Æ (Ê Æ
144 Ú Å 44 ß,%) º: C.55, Si., Mn 1.6, P.1, S., V., Ti.9, Nb.7, Fe. ѾÏÒ Æº: Ù 675 MPa, Ù 59 MPa, ÙÌ 6%. Ð ÒÝ Ó Çº 1 mm 1 mm mm. Ó Ý Cu Ç, ÐÝ Ó µ Í. ݳ ÔÐ 6 1 SiC ÆÅ ÒÊ, É º, Æ º É Ï. Õ ÌÝ (SSRT) Ó º Î ÌÓ, Ó Çº GB/T 1597. Ó ÌÚ Ç Ì (ÑÓ Ìº Ç Ì), Ì Ó Ï Ì± Ï Ì Æ. Ó Ý² ÍÙ SiC ÆÅ À ÌÁ Ì Ê, Æź 8, Ê ÌºÓ Ì, Å Ú Æ. Ê É, Æ º É Ï. ßÆ Þ Û Ê Í, Ý º Æ NaCl, Na SO 4, NaHCO, KNO Á Æ È, Á ÑÆ ph Á. phb 4H ÙÖµÓ ph Áº 9.1. Í Æ ( Æß,%) º: Cl.17, SO 4.85, HCO.16, NO.1. Í Ù Í 99.5% N Ð, ÑÆ N Á CO ÌÀ È CO ÆÔ. Ý CO ± ÔÏ 5%, 1%, 15%, % Á 1%. Ôн Ç EG&G Model 7A Ð Òµ µó ¾. ² ÂÐ, X7 Ç Ó º Ô Ð, Pt º Ð, Á ºÐ (SCE) º Ð, º.5 L. µó Ö ÔÐ 1. V min, Å Ó Ý ±Í ¾Ð ; É ÔÐ Í Ã 15 min ÉÅ.5 mv/s Åß Ôн, Åßн º 1..5 V(vs SCE); ÎÀ Þ Ç Ð (i corr ) Ã. Ð Ò µó Princepton Applied Research Paratat 7 Ç ¾. µ н (E corr ), ÔÐÔ Áº 1 mv, µ º 1 5 1 Hz, ² ZSimpWin V. Æ À Þ ß Ã. SSRT WDML KN µ ÈÈ Ó Ý Ç. SSRT ³, ܼ N ÅÍ Ù Þ ; ³, Ó º Í 4 h. ±ÍÁ CO ÆÔ Ñ¾ Ì Ý, Ì º 1 1 6 s 1, µ µ Ð ½ E corr. ³Ë ÅßÐ (SEM) ÜÝ. нÁºÈÞ È Á ºÐ (SCE). ² ÜÝÕ«(ψ) À SCC, NACE TM 198, É º ψ = (S i S f )/S i ( Í, S f Á S i Æ ºÜ Æ ÝÁ Æ ÝÝ ). Å ².1 Ý ± CO ÆÔ, CO Þ X7 Ç Å ÍÐ Ò º Ê 1, Ð Ò ß Ã 1 Í. 1, CO ƾ À X7 Ç Å Í Ð½, CO ÆÔ Í, Ð (R p ) Ï, Ð i Í, Ü. ß ½Ñ Û, ÆÐ Ü. ß Ð½ E Ü, Ð i Ü Í, Ð Â ÄÁ. CO ÆÔ Í ph Á 1. 1 Đ, Í CO ph ÁÏ, CO ÆÔ Í, ph Á. ß ½¼ Û ÝĐ ¾ß, ß Ð Ü ß ¾. X7 Ç Å Í CO ÆÔ Á Ð CO Nyquist Þ. a Đ, CO ÆÔ Nyquist ÈĐ, ½ ³ ÊÁ ½ ³ Warburg, EIS ³ Þºß, Ð Ð Í ÊÐ Ý Ð Ð½ E ³ ³. CO ÆÔ Í, Ê Ï, Ð E(vs SCE), mv 8 4-4 -8-1 5% 1% 15% % 1% -7-6 -5-4 - - -1 lg(i, A/cm ) 1 X7 Æ ¾ Ì CO Ó Ó ¼ Ï¾Æ Fig.1 Potentiodynamic polarization curves of X7 pipeline steel in simulated Ku erle soil solution with different partial pressures of CO (total pressure consists of N and CO pressures) Ù 1 ¾ Ì CO Ó Ó ¼ Ï¾Æ Â ³ÞÀ ph À Table 1 Fitting parameters of potentiodynamic polarization curves and ph values in simulated Ku erle soil solution with different partial pressures of CO Partial pressure, % R p, Ω i corr, µa/cm ph 171. 11.51 8.9 5 145..78 5.7 1 1. 1.94 5.55 15 881.1 4.64 5.46 69.5 4.49 5.9 1 9.5 74. 5.5
, 1 : X7 Å ½ CO Ã Đ Ë 1441 Z im, /cm 1 8 6 4 (a) 5% 1% 15% 1% Stress, MPa 75 6 45 15 5% 1% 15% % 1% In air - 5 1 15 5 5 4 Z re, /cm 1 4 Strain, % Z im, /cm 1 8 6 4 - (b) 5 1 15 Z re, /cm CO Ý X7 Æ ¾ Ì Nyquist É Fig. Nyquist curves of X7 pipeline steel in simulated Ku erle soil solution with different partial pressures of CO (a) and without CO (b) Ð R t Ï, CO ÆÜ, CO ÆÔ ÜÐ Í. ½  Warburg ± à Þ., X7 Ç CO Í Ð Ò Ê Ø Ã È. Ð CO ͵ EIS ÇÄ ³ Ê, ³ Þºß ( b). Æ CO Ô ÆÐ º ph Á. È ±µ CO Þß Ð Ü Ô À CO Þ Ý Ô.. SSRT X7 Ç ±ÍÐ Å Í CO ÆÔ SSRT Ï, ß 4. Đ, ± (in air) È, X7 Ç Å Í Ù À, Å Ï ½. Í CO ÆÔ Í, ÜÝÕ«ψ Ü Ï, Ï ½ Ü. 4 Đ, Í CO ÆÔ Ç %, ψ Đ Ç ; Ð CO ÆÔ % Ç 1%, ψ Á Í, Ð ÆÔ, Í CO Þ X7 Ç Å Í Æ Ê Í. 5 CO ÆÔ X7 Ç Å Í SSRT н Þ (E corr t) ÅÐ Ï Þ (σ t). 5, CO Üƾ X7 Æ ¾ Ì ĐÄ Ì CO Ó SSRT ¾Æ Fig. SSRT curves of X7 pipeline steel in simulated 5 48 46 44 4 4 8 Ku erle soil solution with different partial pressures of CO and in air 4 6 8 1 Partial pressure of CO, % 4 CO ÓÝ X7 Æ ÛÜÔÅ É Fig.4 Effect of the partial pressure of CO in the solution E corr (vs SCE), mv -66-68 -7-7 -74 on the area reduction of X7 pipeline steel 1 Crack initiation Homogeneous strain Crack growth Heterogeneous strain 1 15%CO SSRT 15%CO %CO 1 t, h 7 6 5 4 1, MPa 5 X7 Æ ¾ Ì SSRT E corr t σ t ¾Æ Fig.5 Curves of E corr t and σ t of X7 pipeline steel in simulated solution under SSRT X7 Ç Í ½ н. X7 Ç º ½, нÖ, Û Ý ¼  (  ٠); 7 h Ò, º ½, н Â, Æ º ½, Û ÏÁÐ Ò ÌÔ,
v k h 44,.'aG, *("a^$ W1, 41eE7, \ f~h6x. N wx.. z CO B O. /, P l ^ P O {! 6 j X7 8O#A M$< D U CO Ol eaf O: ÆpF x> SEM ;. Ca CO Æp f % O (CO % Os Henry nh=p) (5% I 1%) A M$ < D U, X7 8O# x CO (g) = CO (aq) (1) >Æ UZ?7 (! 6a c); [D U CO ÆpU! 1%, x > O? 7as ~ I,? L _K. { O% O (! 6d); D U CO Æp! 6 U, X7 8O# x >as! T L f x `, x > L f. (! CO (aq) H O = H CO () 6e, f). Y j! X7 8O# le. DW, * x >a sv I?7Lg,! 6e I f gasj j_ H CO = H HCO (k = [H ][HCO ]/[H CO ]) () Lf. }* K! 4?8,?YW CO Æp F X7 8O# J < m ~H L f. Æ E, CO Æ HCO = H CO (k = [H ][CO ]/[HCO ]) (4) R X7 8O#A M$< D U SCC f, CO D! Q D U 4 W a f N : N CO, CO Æp 6x, x>lf!~h, SCC 144 " 1 6 X7 7N" CO oebwx SEM `r Fig.6 Fractographs of X7 pipeline steel in simulated Ku erle soil solution with CO partial pressures (a), 5% (b), 1% (c), 15% (d), % (e) and 1% (f) (ductile fracture brittle fracture)
1 : X7 Å ½ CO Ã Đ Ë 144 H CO, HCO Á CO. () Á (4) Í Çº ß k 1 k, Æ Í CO Å. ³ Ý Ð, Đ H O µ. Ð Í CO, H CO, HCO Á CO Ôº Õ «±, ±, Ê. Ü CO, ƾÜ, Æ º ÏÒ Ù¾, ph Á Í, ¹ Í H Í «. H CO Á HCO ¹ É Á ¹Ð½ E [17] : H CO e H HCO (E =.6 V) (5) HCO e H CO (E =.856 V) (6) 7 X7 Ç Ð Í ¹ SEM. 7 ž, Ð Í Æ CO, X7 Ç Æ ¾ ¹. ÝÆ Á ÅÐÐ ¼Ç, X7 Ç Æ ß, ź CO Ô Ù ½². Liu Á Mao [18] Â Æ Fe(OH). Í CO ± Fe(OH) ¹ ¾ FeCO. ÏÒÇ, н FeCO È Ð Ò. CO ± Fe(OH) ¾ FeCO Fe(OH) Ý. Ø ± Û, Ð ± FeCO ¾ ÒÃ. Æ ß Ö ¾ Fe(OH), É º FeCO, ÑÉ ¾ ÒÃ, ³ß : Fe Fe e (7) Fe OH Fe(OH) (8) Fe(OH) CO FeCO H O (9) FeCO HCO Fe(CO ) H (1) à Æ, X7 Ç CO Í ÒÃ Û Ý Ã ²Æ À¹Ò. CO ÆÔ Ü, ¾ H CO Á HCO Ù Í, Æ¾Ü X7 Ç ß, ± 1 Í i corr ¼ È. CO Å Å Í, X7 Ç H O µ Áß ¹ H ¹. ¹ Đ H ĐÀ () Á (1), ³ È H ÌÐ Ý Ã. Ýн, Í CO ÆÔÆ¾Ü () Á (1), Ü H ÌÐ Ý Ã Á ¹, Ð., ³Ð Ò È H ¹ Á H O µð Ò È, Ð ÒÃ Ð Ý²Æ ¹Ò, Ñ (1) ¹ÒÐ Ò. : H O e H OH (11) H e H (1) H CO e H HCO (1) 7 X7 Æ ¾ĐÄ Ì SEM Ö Fig.7 SEM morphologies of corrosion products of X7 pipeline steel in simulated Ku erle soil solution without CO (a) and with partial pressure of % CO (b) H H H (14) ¹ H ³ Ï Í ĐÔ [19]. Ý Ð, ß Fe, Đ ; Đ H O µ Á ¹, ³. ¹ H µ Å Ï Æ : ÆÌÈ Ã ¾ H ; ÆÎ Í ¾ºÆ Õ H µ, Ì ÂÌ Ï ÍÝ Ã, µ Ý ½, Æ H Æ Æ, «²,  Ù., ³ H µ õ Ï ÍÝ. Æ, Ï X7 Ç CO Å Ð Í, CO Á Ï,  ß, ¹ H ƾÂ. Ï ½ Ⱥ¹Ä ß Ã È, Í CO Æ Ô Ü, ¹ÄÔ Í, ± SSRT Æ. OCP(open circuit potential) н, Í Cl Á SO 4 Æ ÅÐ CO Ô, Û Ý ¾, Í ¹ ph Á
1444 Ú Å 44. ¹ H Â Û Àµ, Ë Ý ½,  ٠Á, ÆÄ Ü. ÏÏÒÆ ÁÐ Ò» Ô ¼ºÏÒ Ð ÒÔ, Û ÝÆ ÃÐ Ï Í½² Ô À. CO Í, Û Ý ¾ Ð Ù, Æ Á Õ ( 7b), Æ, Ï Í ÝÚ,. Ï Í, X7 Ç ÏÐ Ò ÏÒ. µ Ô Èº: Û Ý Ð Ò, Ñ ¾ µ ÍÙ», ÉÚ Ý µ, Æ, µ ² Ð Æ, ÂÌ Ý Ô Ü½È, µ Þ ÃÆÀ Á Ô, Àµ Ï, Æ ½È¹Ô,  ÛÜ. Ð Ò ÏÒ, Ý ½ÈÉ Á, Ý ÅÐ Ò Æ, Ý º ¾ µ Ï ½È []. Æ X7 Ç CO Å Í Ï, Ï«Û Ù, Ð ÒÔ, ; ¾ Ï» Ûµ ÃÏ, ½ µã, Æ ÛÜ. 4 (1) X7 Ç Å Ð Í, CO ±, ¾ ÒÃ, Ü X7 Ç. () Ýн, Í CO ÆÔƾÜ, Û, Ü X7 Ç Ï. Ï ½ Ⱥ¹Ä ß Ã È, Í CO ÆÔ Ü, ¹ÄÔ Í. () X7 Ç «Ù Ï, н,, Ï» Ûµ ÃÏ,, ÑÎ Æ ÛÜ. ÚÅ [1] Albarran J L, Aguilar A, Martinez L, Lopez H F. Corrosion, ; 58: 78 [] Koh S U, Kim J S, Yang B Y, Kim K Y. Corrosion, 4; 6: 44 [] Eadie R L, Szklarz K E, Sutherby R L. Corrosion, 5; 61: 167 [4] Zhao M C, Yang K. Scr Mater, 5; 5: 881 [5] Yu F, Gao K W, Su Y J, Li X, Qiao L J, Chu W Y, Lu M X. Mater Lett, 5; 59: 179 [6] Parkins R N, Zhou S. Corros Sci, 1997; 9: 159 [7] Parkins R N, Zhou S. Corros Sci, 1997; 9: 175 [8] Niu L, Cheng Y F. Appl Surf Sci, 7; 5: 866 [9] Li M C, Cheng Y F. Electrochim Acta, 7; 5: 8111 [1] Contreras A, Albiter A, Salazar M, Pérez R. Mater Sci Eng, 5; A47: 45 [11] Parkins R N, Beavers J A. Corrosion, ; 59: 58 [1] Li M C, Cheng Y F. Electrochim Acta, 8; 5: 81 [1] Gu B, Luo J, Mao X. Corrosion, 1999; 55: 96 [14] Gonzalez Rodriguez J G, Casales M, Salinas Bravo V M, Albarran J L, Martinez L. Corrosion, ; 58: 584 [15] Park J J, Pyun S I, Na K H, Lee S M, Kho Y T. Corrosion, ; 58: 9 [16] Li X G, Du C W, Liu Z Y. Corrosion Behavior and Eexpremential Study of X7. Beijing: Science Press, 6: 1 (ÉÎ, ØÅÖ, É. X7 Æ ¹ ÒÜ ±. : Ñ É, 6: 1) [17] Linter B R, Burstein G T. Corros Sci, 1999; 41: 117 [18] Liu X, Mao X. Scr Metall Mater, 1995; : 145 [19] Cheng Y F. J Mater Sci, 7; 4: 71 [] Liu J H, Li D, Liu P Y, Guo B L. J Mater Eng, 5; (): ( ØÍ, É Õ,, Á., 5; (): )