ÅÔ½ß (electrochemical noise EN)

Transcription

1 29 6 Ë «ÁÖ Vol.29 No.6 29  12 Journal of Chinese Society for Corrosion and Protection Dec Ù ½ ßÝ «ĐÖ Ü Áà 1 À 1,2 ÂÄ 1 (1. Ê ÈÕÏ Õ 122; 2. ß Ï³ ¾ß 3452) : ¼ Î ÆÕ¾ ²º Ü ÆÅ Ó (CPT) ÆÞ Ü ²» ASTM Õ Ê Ð ½¾ ² Å ½¾ Ë È Æ ÅÐ CPT ¼ Î Ü ² 8 Î º CPT Ô : Ü Å Ó ÆÕ¾ ¾ ½ Ë Ü ³ : TG174.3 ºÐ : A : « ÅÔ½ß (electrochemical noise EN) Á ÅÔÐ É ÜÅ É É Ô ½± Ú Î ³ÐÍ ¼º 1968 Á Iverson [1] Ù Ý Ý ³Ð Í Â³ EN Æ 1981 Á Hladky [2] Ý ³¼ ÅÔ½ßÆ ÍÚ ¾± Ù Ý Ù ½ ¾ Ý ½ß º «½ßÎ 1 Hz Ö ¹µ Å ¼½ß Ù ÌÄ 1986 Á º [3]» ³ ÅÔ½ß Ä EN Ï Ä [4] EN»±É ı ÍÇ Ç ± Ò ÅÔÉ Þ Ã À Þ É Ç» ѵÀ Å À Í Í Ù ÖÁĐÆ (TGSCC) Đ Æ (IGSCC) µú ÅÔ È µë  (MIC) Ê Ç µ [5] Ö ¹µ Ç ÙÕ ÙÕ Đ Ú ÙÕ ÙÕ Ô É Û º ÔÒÜ «ÊÈ ºÈ ÒÔÒÜ Û Ò (critical pitting temperature CPT) Å Ú : Æ : Á ÍÆ Æ1945 ÃĐÆÕ ÆÚ Đ Ç Â ²¾ : Á ÍÆ wengyj@cup.edu.cn Ô½ß Í Ù ÐÛ º Ù É Í Æ [6,7] CPT ¹µ/È ½É Ï ¹ Ö¹µÆ Ã Ï Ö Ò ÐË ¹µ FeCl 3 ±Ô Ý CPT ÐÛ ¾ ASTM» ÐÛ [8,9] Ý Ï Ö Ö Î [1]» EN ¹µ CPT ÝÐÛ ³ ± Ö ¹ CPT ÝÐÛ 2 Þ Ý 8 Í Ë Â ÅÔÁ Ö 1 É 16Mn X7 ºÎ Æ ºÎ² 45 N8 J55 2CrMo Ë º Ù µ»± Q Ð ÛÏ ¹Æ Å 2.5 cm 5. cm.2 cm Ì 1 cm 2 Å 12 ÙÂÆ ÝÔ ASTM G48- Ð C ÈÆ ÈÐ g FeCl 3 6 H 2 O+6 ml H 2 O+16 ml HCl (36.5% 38.%)» CS3P ÅÔ É ÅÔ½ß ¾±» Î 1 Hz Ý Æ Ö 1 cm ½ Ag-AgCl Ø ½É¹ ¼ ZRAÅÛ [5] ¾± ½ß ¼½ß Ý ½É Ô Ò 51A Ì ± ±.1 Å Æ Ä 3 Í 85 5 s 1 ¾± É 5 ¾ Æ»

2 422 ɾ ÀÔ 29 Table 1 Physical and chemical properties of several oil industrial steels materials mechanical performance composition /mass% σ b /MPa σ s/mpa σ 5/% C Mn Si else 16Mn > X > Mo(.2), Cu(.2), Nb(.6), Ti(.6) > Cr(<.25), Ni(<.25) N >2 P(<.3), S(<.3) J >2 P(<.3), S(<.3) 2CrMo 9 7 > Mo(.15.25), Cr(.8 1.1) Q > >45.6 <2. <1. Ni(8 11),Cr(17 19) ¾» 45 min Ó ½ ß¾±» ÐÛ 3 ± 3.1 Ø Ø Õ ¼ 8 ͹µº É ¼½ß - 1 ½ß ¼½ßÅÒ ÆÀÅ Ý Ð ÖÇ ÖÍ ¼ Ó ¼½ß³Ð Ê Å ÍÞ «Ù Å Ä Å½ß ¼ Ê Á ¹µ CPT ¹µ ½ß ¼ Ê Ò Ø Ç ¹µ½ß ¼³Ðº 7 ËÓ ² ÀÖ ÒË 3.2 Ø Ò - µû ¼ ¾ Ò É Ò 1 É½ß - É Æ ½ß - Ò 3 9 à ÖÇ Æ É É.999Å T = t (1) É T Ò t ¾± s Î [1]» ½ß Á É ¹ µ CPT ÐÛ À ASTMG48 ÐÛÚ Ä ± ÏÍ Ö Ù» ÅË À ÐÛ ºÖÆ ÝÙ ß Ò 8 Õ Õ É 256 Õ ¼½ß ÆÀ (MEAN) Ê (SD) Å ½ ÕÉ Ò Å X7 ÏÍ 2 ÖØÛ MEAN Á Ö SD Á Ò Å ¼ SD Á Ò S É CPT Ò» Origin7.5 Ð «/ Ä analysis/calculus/diff/smoothå» Ó Ê 3 ÄÅÀ ÏÍ 3 à ͹µ CPT Í ÆÒ:Q235 (51.<16Mn (51.5)<45 (54.3)<2CrMo(55.4)<N8 57.8Å< X7 58.Å<J Å< Å( É À Æ CPT Ê ) 3.3 Ó Q235 16Mn X Ð 4 ͹ µ Ò º 55 Ë ASTM ÝÔ É Ç ¹ Ì Å Ý Ü CPT ³Ú È Ò Q235 16Mn CPT X Ð CPT 45 min Ç º Q235 16Mn Ì Í Øº X Ð Í ( 4) 3.4 ŵ ÓÕØ Ó ½ß Đ CPT Å X7 ¼½ß 5aÅ Ò - ± Å ÐÛ ³Ï CPT 5bÅ 5b ³ÏÍ X7 CPT 58. ³ Ú Ä ¹µ Ó ³Ú 1 Å ÀÓ Ò Æ ÒÖ 3.5 й Î Ä Ä ÅÔ½ß Õ À ¹Ç Ë Æ ³ĐÖ ¹ [11] 6 Ì 45 PSD Ò ( ½ß W) (k) Á [12] Ö Ò Å º 53» ¼ Ê SDÅÁ ³Ú ØÐ ËÎ Ä ³ ݹÏ

3 6 À Ì : ÆÕ¾ Ü Ü Å Ó (a) (b) (c) (e) (d) (f) (g) (h) Fig.1 Potential and current noise of materials in continuous heating a«16mn, b«45, (c) 2CrMo, (d) N8, (e) J55, (f) Q235, (g) X7, (h) 18-8 stanless steel mean / A cm MEAN SD Fig.2 Mean and SD for current noise of X7 steel in continuous heating 6 SD derivative value of current SD CPT derivative value of current' 1sd Fig.3 Calculation process of CPT for X7 steel

4 424 ɾ ÀÔ 29 W Fig.4 Surface morphology of steels with different CPT after dip-in tests in ASTM solution at 55 (a) Q235, (b) 16Mn, (c) X7, (d) (a) 5 22 (b) SD Derivative Value of Current' SD CPT Fig.5 Calculation of CPT for X7 steel in continuous cooling (a) potential and current noise, (b) 2.x x x1 6 8.x1 5 4.x1 5 calculation of CPT Fig.6 Frequency domain indexes for 45 steel 4 W K 1Å ÅԽ߻±³¹µÄØ Ç Ù»±³ Û Ò ¾ ÐÛ ± Ö k Ï 2Å Ý ½ß ¼ Ê Ò É ¹µ Û Ò CPTÅ 3Å Ö½ß ¼ À É ¾ ³ 8 Í ¹ CPT Í 5 7 Ö ½ Ñ» derivative value of current SD [1] Iverson W P. Transient voltage changes produced in corroding metals and alloys [J]. Electrochem. Sci., 1968 [2] Hladky K. Corrosion monitoring [P]. US Patent 4, 575, 678 [3] Eden D A, John D G, Dawson J L. Corrosion monitoring [P]. US Patent 5, 139, 627 [4] Eden D A, Carr R N, Dawson J L. Method and apparatus for producing electrochemical impedance spectra [P]. US Patent 5, 425, 867

5 6 À Ì : ÆÕ¾ Ü Ü Å Ó 425 [5] Eden D A. Electrochemical noise-the first two octaves [A]. Corrosion/23 [C], 23: 386 [6] Dong Z H, Guo X P, Zheng J S, et al. Features of ECN of localized corrosion for 16Mn steel [J]. J. Chin. Soc. Corros. Prot., 22, 22(5): ( Ã, ½ É,. 16Mn Ì Ç Ð º [J]. Ì Â, 22; 22(5): ) [7] Hu L H, Du N, Wang M F, et al. Monitoring the initial pitting behaviors of 1Cr18Ni9Ti stainless steel by electrochemical noise and electrochemical impedance spectroscopy [J]. J. Chin. Soc. Corros. Prot., 27; 27(4): ( Ã, Ñ,. Ç Ð Ç 1Cr18Ni9Ti µñ [J]. Ì Â, 27; 27(4): ) [8] ASTM. G48-, Standard test methods for pitting and crevice corrosion resistance of stainless steels and related alloys by use of ferric chloride solution [S]: 2 [9] ASTM. G15-99, Standard test method for electrochemical critical pitting temperature testing of stainless steels [S]: 1999 [1] Heyn A, Goellner J, Burker A. Determination of critical pitting temperatures using electrochemical noise [C]. Corrosion/24, 24: 4462 [11] Zhang J Q, Zhang Z, Wang J Q, et al. Analysis and application of electrochemical noise. (I). theory of electrochemical noise analysis [J]. J. Chin. Soc. Corros. Prot., 21; 21(5): (,, Ñ. Ç Ð Å -I. Ç Ð Å³ [J]. Ì Â, 21; 21(5): 31-32) [12] Mansfeld F, Lee C C. Comparison of electrochemical noise and impedance data for passive systems [A]. Corrosion/1999 [C], 1999: 195 COMPARISON OF CRITICAL PITTING TEMPERATURES FOR OIL INDUSTRY STEELS USING ELECTROCHEMICAL NOISE WENG Yongji 1, LI Weifeng 2,1, LI Xiangyi 1 (1. Mechanical and Electronic Engineering, China University of Petroleum, Beijing 122; 2. CNOOC Engineering Ltd, Tianjin 3451) Abstract: A newly experimental method is proposed for determination of the critical pitting temperature (CPT) of metals. The current noise of steel coupon is measured during the continuous heating process in ASTM standard solution. CPT is determined based on assessment of the maximal transition point in the item of standard deviation of current noise. The CPT values of eight steels commonly used in oil industry are measured by this quick and easy method. Key words: oil industry steels, critical pitting temperature, electrochemical noise, standard deviation of current noise, experimental method.