Ð Ð 5 ² Ô Â Vol. No.5 1 1 ß Journal of Chinese Society for Corrosion and Protection Oct. 1»³ AZ91 Ð Ó± CO /HCO ¹Í Ú ¾ (± Ý Ë Ë Ó Á Ò ÀÅ ¼Á 1116) : ÔÆ À Ó ÀÓÆ À» À AZ91 É Đ Ú Ø ¾ CO /HCO ÉÕ ± (SCC) ½ Đ ± É ph AZ91 É Ü Ò Ã AZ91 É Đ ÀÕ ÅÎ Û À Ð Î Ò» Å ºØ Å»¼ Å ¼ Å Đ Ú Å Å Đ SCC µ Ë : AZ91 É CO /HCO É Æ Ø : TG17.6 Æ Ý : A µä : 15 457 1«5 47 7 1 È ³ ³ ÎÇм 1 À Á³³ ¼ [1] ¾ Ö ³ Ó ³Æ È ²¾ ¹ 1 À Ä ÑÎ Ì Ý º È ß [ 5] È Å É ÞÞ ÛÑ Ö ĐÈ Ï º ³± ³ Ê È Ä ÚÏÇ É Ô ( CO ) È º º (CO Ò ¾ ³Ó H + HCO CO ) Ç / Ô ÂÈ ¼ É ÌÞÈ ¼»Ä Cl Ô [6 8] Þ / Ô ¼ ³ Ô ÈÓ Ï ÈÔ [9] HCO Ó Ó ÅÐ Vermilyea [1] HCO (OH) Å Î : 9-9- Ô Đ : (54996) ¾ ½ Ñ : Í ÆÐÆ1985 Æ Æ Ì Õ Ã ½ : ÒÆ, E-mail: wanjianqiu@imr.ac.cn ÉÔ À ÂÅ HCO Ï À Ú Ñ AZ91 È Ù ½ CO /HCO ÈÔ ÓÅ Ò ¼ Ð Ô ¼ AZ91 È Å Å (mass%) 8.89 Zn.78 n.1 Ni<.1 Fe. Cu. Ð ÓÅ Å Ò Å ÃÙ ³À ŲÞ. cm 1. cm SiC µ Ì Å µº ÆÃ Ú ÃÙ Ë Ü 1 Ü Ë 5 mm 8 mm.5 mm É È É ¹ Æ Å ½ 4 µ Ù Õ Na CO /NaHCO ÈÔ Å Å ph ( ÆÍ SARTORIUS, PB-1) Fi.1 Schematic illustration of the tensile sample (dimensions in mm)
48 Ò À Na CO /NaHCO =/.1 mol/l (ph=8.7 1 ) Na CO /NaHCO =.1/.9 mol/l (ph=9.1 ) Na CO /NaHCO =.5/.5 mol/l (ph =9.96 ) Na CO /NaHCO =.9/.1 mol/l (ph=1.8 4 ) Ó «Õ 1 h Potentiostat/ Galvanostat odel 7A Ó Í AZ91 È Í 4 µ Ù ÈÔ Å ½ Ó Ô, ³ÀÓ AZ91 È ½Ó µ ¾ Ó Ó (SCE) Å ².1667 mv/s Ú AZ91 È Ó Å² 5 ml Na CO /NaHCO =.1/.9 mol/l(ph=9.1) Na CO /NaHCO =.9/.1 mol/l (ph=1.8) µ È Ò d ¼ Å Ô ÒÐ ßÂ É ¼ YL1- ¹ Æ AZ91 È 1 1 6 s 1 Ë ÈÔ ¼ 5 Ú¼ Ô ¾Ô [8] ¹ EPA 161 Ó ÆÅ ÍÅ ÒÆà ºÇÒØ Å Ó 15 kv Ó Ï 1 na Å 45 µm 45 µm ¹ ESCALAB 5 X ¼Ó ÞÍ (XPS) Å Å Kα=1486.6 ev, Spot Size=5 µm, Pass Enery=5. ev Xpspeak4.1 Ö ¼Ã¹ 1s O 1s C 1s Þ Ð Ó ( ) Å Ø Å ± à ٠РŠ½ Á Ù s Å C Ø 85 ev Ò C Õ (84.6 ev) C Ø ÞÖ.4 ev ¹ Ø ÞÖ Å.4 ev ¼ É ² ÓÆ (ESE, XLFEG)» µ ºÆÃ Ý Ò ºÇ Ð.1 AZ91 È Ù Õ Na CO /NaHCO ÈÔ Å Ü aå Ù ÈÔ Ó Ò È ph º Ü bå È ph AZ91 È ¹ Æ ßÅ ph Ô ßÅ ² Ù È ph AZ91 È Ó Ì ßÅ Í ßÓ Ï Û E SCE /V E corr,sce /V.4 (a). -.4 -.8-1. -1.6 4 # # 1 # -. -8-7 -6-5 -4 - - loi / A cm - -1.5 (b) -1.55-1.6-1.65-1.7 1 # # -1.75 8. 8.5 9. 9.5 1. 1.5 11. 11.5 ph # Fi. Polarization curves of AZ91 alloy (a) and relationship between corrosion potential (E corr) and ph values of AZ91 alloy (b) in different Na CO /NaHCO solutions. Ç ß Ê Ç AZ91 È Na CO /NaHCO =.1/.9 mol/l (ph=9.1) Ü aå Na CO /NaHCO =.9/.1 mol/l (ph=1.8) Ü bå µ È Ò d ÆÃ Ó Æ (EPA) ºÇ Ù Ò Na CO /NaHCO =.1/.9 mol/l ÈÔ Æà  º ÂÅ Ð Na CO / NaHCO =.9/.1 mol/l ÈÔ ÆÃ Ä Í Ô Ê ÂÅ «Ñ «ÂÅ Å Ô Ê Ü c f Ü a Þ Ø Å Ò»ÄØ O Ü a Å ÔÂÅ Þ Ä Ô Ü cå ÔÂÅ Þ Þ Ô Þ Þ Ü då O Ü a Þ Þ ³ ÔÂÅ Â ÔÂÅ ÔÐ Ø O Ü eå; C Å Ü få Ü 4 XPS Å µ ÈÔ AZ91 ȻĠ(OH) (OH) [7,11,1] (OH) (OH) Å Ù Ï (OH) Å Ù º (OH) 8 H O 4 # #
5 T : 4 AZ91 Q B CO /HCO q %` _ 5 = 1 49 Fi. Surface morpholoies and EPA elements distribution of AZ91 alloy after days immersion in Na CO /NaHCO solutions with the chemical composition ratio of: (a,c f) Na CO /NaHCO =.1/.9 mol/l(ph=9.1); (b) Na CO /NaHCO =.9/.1 mol/l (ph=1.8) 1.4x15 (a) O 1.x15 1s C 1s O KLL Auer 4.x14.x14. -.x14 14 1 1 8 s 6 4 (OH) s 4x1 x1 x1 1x1-6 55 5 7x1 (OH) (d) 6x1 (OH) 4.5x1 4x1 x1 x1 x1 1x1 85 8 75 bindin enery /ev 7 65 (e) (OH).x1.5x1.x1 1.5x1 6 55 5 45 4 85 bindin enery /ev 8 75 7 65 bindin enery /ev Fi.4 XPS analyses of AZ91 alloy after days immersion in Na CO /NaHCO solutions with the chemical composition ratio of (a c) Na CO /NaHCO =.1/.9 mol/l (ph=9.1) and (d,e) Na CO /NaHCO =.9/.1 mol/l (ph=1.8) z" ws x 5 AZ91 P A ~ f B _ P p $~ ^ 4 <_ A 4 8 e n G p ph _.! p : ph _5! AZ91 P A ^ _G). y;:b$_eu ^4 y; :k y X Oe G ne. G raap*5_ I $ \ ph 5! P A _ ^ 4 < Z we.4 Wrhk~`Q *u P p Q ^ _ G).N K y..5x1 4x1 x1 4 4.x1 5x1 1x1 5x1 6x1 45 bindin enery /ev (c) 5x1 bindin enery /ev 7x1 6x1 KLL Auer 6.x14 (b) 7x1 1.x15 8.x14 8x1 1s #_Q &YoÆ (ESE).O/6!x 6 ff! p ; NN K y # x K U AU vx - 8 (x 6a,6b) x K U _ ; " $, ' E([ y ; : CO /HCO j s 1 _ U G p _ ph 5! N K y # x U vx -; U _ X _o+ (x 6b) ^ jy ;! NP y ; " y ; 7 _ I (x 6c,6d) b Q & Y o Æ (ESE) /6 ^ _ G). N K _y # B X. O (x 7)! p ~ *u ph _
$4 < n H 8 4 (a) stress 5 time to failure 1 5 1 8 6 8. 15 8.5 9. 9.5 1. 1.5 11. 1 11.5 (b) elonation 1 elonation / % stress / P a 14 1 time to failure /h 16 reduction of area 16 8 1 6 8 4 reduction of area /% 5 4 8. 8.5 9. 9.5 ph 1. 1.5 11. 11.5 ph Fi.5 Evolution of mechanical properties of as-cast AZ91 alloy with the ph values of the corrosion solutions (a) stress vs. ph and time to failure vs. ph; (b) elonation vs. ph and reduction of area vs. ph Fi.6 Fractoraphs of AZ91 alloy in various solutions: (a, c) AZ91 alloy tested in Na CO /NaHCO =.1/.9 mol/l (ph=9.1) solution; (b, d) AZ91 alloy tested in Na CO /NaHCO =.9/.1 mol/l (ph=1.8) solution <Q $ AZ91 PA ~9L ^4 < 7( m<j AZ91 PA ~ Gp _ ; U v. O s SA A d. β ; 8U 8 ; (x 7a,7d) $ \U j m<h._ ; Ws'.?/; /; {'~ u_ ; " ' ~ SCC 7 ( (x 7c) : G p ph _5! AZ91 P A _ < X! U _ ; _X8nL ; _:s\ o+ (x 7b,7e) x 4.1 \ R Z S -HO p _ Pourbaix x [1,14] *U G~8 ~ Na CO/NaHCO Pp $ AZ91 PA $X_ <8!e (OH) CO (OH) % [15] CO (OH) _ s_ 9X & (Ksp ) Ksp (CO )=6.8 16 Ksp -? CO n 5 P, = j s ([]) &! f ) E () (4) db^e ((OH) )=5.61 1 (OH) f _ 1 CO + CO [(CO ] = ) K sp (CO ) 6.8 16 = [CO [CO ] ] (OH) + OH 4 [(OH )] = Ksp ((OH) ) 5.61 11 = [OH ] [OH ] [OH ] = 1pH14 (1) () () (4) ~ NaCO/NaHCO Pp $ CO +>7 X j"_ Na CO o, n j"_ NaHCO. o,
5 T : 4 AZ91 Q B CO /HCO q %` _ 5 = 1 51 Fi.7 Lonitudinal- section observations of the aue part of (in depth direction) AZ91 alloy after SSRT at the rate of 1 16 s1 in various solutions: (a c) different parts of the same sample tested in.1 mol/l NaHCO (ph=8.7) solution; (d) AZ91 alloy tested in Na CO /NaHCO =.1/.9 mol/l (ph=9.1) solution; (e) AZ91 alloy tested in Na CO /NaHCO =.9/.1 mol/l (ph=1.8) solution + HCO H + CO (5) f [16] 1.5 K(HCO ) = 1 ~ *u j s q _ G p CO HCO, = j s P ph r* u -A $ X.?_ <8!e *u W Na CO /NaHCO=/.1 mol/l(ph=8.7) _p 1 Z P p NaHCO P : 4^ P ph=8.7 f )E () (4)! ^? (OH) CO f 5L _ P, = j s ([ ]) &.7 [(CO ] = 6.8 1 ).74 [(OH ) ] = 5.61 1 z! ^ [(CO ] > [(OH )] ) - ~ P p (OH) e ~ : $ X? F >W *[ E! z[e AZ91 P A ~ f B _ 4 ) P Q $ (OH) e j CO? <8 $ X t ^, (x ) n X, o= ez (XPS)(x 4) _ G G 9 W * -J d b~8 AZ91 P A ~ Na CO /NaHCO p _ <8 / L (OH) (OH) } % -H O p _o -ph x [1] Z P ph z e: A $ t ^ ~ <8 $ W (OH) _.ER~ Z P ph z!: (OH) v7 O 4..& AZ91 nt"u\ Z G p _ ph ze (Na CO/NaHCO =/.1 mol/l(ph=8.7) Na CO /NaHCO =.1/
5 Ò À.9 mol/l(ph=9.1)) AZ91 È Þ (Ü 5) ± -H O Ô Ó -ph Ü [1,14] (OH) ¾ ph 8.4 ß Na CO /NaHCO = /.1 mol/l(ph=8.7) Na CO /NaHCO =.1/.9 mol/l (ph=9.1) µ Ô ph ¹ Å µô (OH) º (OH) º Ú È Û ¾ Å AZ91 È Ñ Þ Ã; (Ü 7d) AZ91 È ¾ H Ä Ô½Û Ô Ù ËÏ Ò È Ã ph ¾ÑÅ Ç Ô ¾ O ³ ʹ ¾ (OH) [1] (OH) Ò (OH) Å È (OH) Ù Ï (OH) Å Ù ³Ò½Û H ¾ÝÄÀ ¾Ï [7,11,1] + V + 6 (6) V + H H H + V H (7) H + H O + e (8) Ã Ù Ý Ṁ Ù Ù V Å ÑÃÈ Ù V H Å Ñà ٠( ) à ŠÑÃ Ã Ù Ý H H à ŠÑà ٠H Å Ù Ñ e Ó Ô Ï V H Ò H Ù ³± Í H Ù ÚØ ³± Ô³ Å β Å H ¾ Å Ï ¾ º ÙÀ Ï β (Ü 7a) º Đ Ð ¾ Ð e ³± È ÜÈ ÓÅ Ç º ÜÈ Ô ÖÚ Í AZ91 È ± -H O Pourbaix Ü [1] ph>9. È ÚÏ O º Ê Ô Na CO /NaHCO =.5/.5 mol/l (ph=9.96) Na CO /NaHCO =.9/.1 mol/l(ph=1.8) (OH) ¹¹ O (OH) ± Í H ÒÓ Ô Û ÊÕ H º ³± Ù È ph ¾ Û È AZ91 È Ã H ¹ º H ÚÏÛ Ò 5 ÐÜ (1) Na CO /NaHCO ÈÔ ph AZ91 È ¹ Æ ßÅ Ó Ì ßÅ Í ßÓ Ï Û () Ù Õ Na CO /NaHCO ÈÔ AZ91 ȻĠ(OH) (OH) () Ñ Â AZ91 È Ô Í¾Ú Í¾ Đ ¹ ³ º»» ß³ Ù Đ ³ ¾ SCC (4) Ô ph AZ91 È Í¾ Ó ¹ Ò ÈÕ [1] Liu Z, Zhan K, Zen X Q. Theory and Application of -based Liht loy []. Beijin: China achine Press, (, «², ³Å. Ê «ºÃ Á []. «Ç ¹, ) [] Wan F P, Li X G, Lin C, et al. Atmospheric corrosion behavior of AZ91D manesium alloy in Beijin area [J]. J. Chin. Soc. Corros. Prot., 4, 4(6): 45-49 ( Û,»², É. AZ91D Ê «Î ¾ [J]. ³ Õ Ã, 4, 4(6): 45-49) [] Lin C, Li X G. Initial corrosion of AZ91D manesium alloy in atmosphere containin SO [J]. Chin. J. Nonferrous et., 4, 14(1): 1658-1665 ( É,»². AZ91D Ê SO Î Ê ³ Ð ¾ [J]. ³ Ì, 4, 14(1): 1658-1665) [4] Chen J, Wan J Q, Han E H, et al. Effects of dust and salt particles on the formation and spreadin of micro-droplets [J]. Corros. Sci., 8, 5 (5): 1449-1459 [5] Chen J, Wan J Q, Han E H, et al. In situ observation of the formation and spreadin of micro-droplets on manesium and its alloys under wet-dry condition [J]. Corros. Sci., 7, 49(): 165-164 [6] Wu Z N, Li P J, Liu S X, et al. The actuality of study in manesium corrosion [J]. Foundry, 1, 5(1): 58-586 (Æ,»ÔÐ, Î. Ê Ó [J]., 1, 5(1): 58-586) [7] Chen J, Wan J Q, Han E H, et al. Corrosion behavior of AZ91D manesium alloy in sodium sulfate solution [J]. ater. Corros., 5, 57(1): 789-79 [8] Chen J, Wan J Q, Han E H, et al. Effect of hydroen on stress corrosion crackin of manesium alloy in.1
5 Ì Đ : AZ91 É Đ CO /HCO Õ ± ½ 5 Na SO 4 solution [J]. ater. Sci. En., 8, A 488(1-): 48-44 [9] Gulbrandsen E. Anodic behaviour of in HCO /CO buffer solutions. Quasi-steady measurements [J]. Electrochem. Acta, 199, 7(8): 14-141 [1] Vermilyea D A, Kirk C F. Study of inhibition of manesium corrosion [J]. J. Electrochem. Soc., 1969, 116(11): 1487-149 [11] Fairman L, West J. Stress corrosion crackin of a manesium aluminium alloy [J]. Corros. Sci., 1965, 5(1): 711-716 [1] Chen J, Wan J Q, Han E H, et al. States and transport of hydroen in the corrosion process of AZ91 manesium alloy in aqueous solution [J]. Corros. Sci., 8, 5(5): 19-15 [1] Pourbaix. Atlas d Equilibres Electrochimiques []. Paris: Gauthier Villars, 196 [14] Son G L. Corrosion and Protection of anesium loy []. Beijin: Chemical Industry Press, 6 ( ½. Ê Õ Ã []. «Ç Ç ¹, 6) [15] Lide D R. Handbook of Chemistry and Physics []. CRC press, [16] Zhan X Y. Handbook of Practical Chemistry []. Beijin: National Defense Industry Press, 1986 («Ö. Ç È []. «Ç ¹, 1986) STRESS CORROSION CRACKING BEHAVIORS OF AS-CAST AZ91 AGNESIU ALLOY IN CO /HCO SOLUTIONS HUANG Fa, CHEN Jian, WANG Jianqiu (State Key Laboratory for Corrosion and Protection, Institute of etal Research, Chinese Academy of Sciences, Shenyan 1116) Abstract: The stress corrosion crackin (SCC) behaviors of as-cast AZ91 manesium alloy in CO /HCO solutions were investiated by electrochemical test, immersion test and slow strain rate test (SSRT) respectively. The results showed that the stress corrosion crackin sensitivity of as-cast AZ91 alloy in CO /HCO solutions decreased with the increase of ph values of the solutions. The surface was covered by a film mainly composed of (OH) and (OH). (OH) could be dissolved in alkaline solutions and O enendered. Pittin was the main crack source of AZ91 alloy in such solutions. The crackin of β phase also resulted in microcracks in the matrix. icrocracks initiatin at the bottom of pittin combined into a main crack. The main crack propaated by coalescence of the existin microcracks ahead until the SCC fracture occurred. Key words: AZ91 manesium alloy, stress corrosion crackin, CO /HCO solution