采用矩形缝隙装置，研究了阴极极化条件下本体Na2SO4溶液浓度、pH 值以及本体溶液的含氧状况对模拟剥离涂层下溶液的化学和电化学环境的影响，分析了剥离区域内X70钢表面发生的电化学反应。结果表明，增加本体Na2SO4溶液的浓度虽然有利于阴极电流在剥离涂层内传输，但会导致钢板表面钝化膜的破坏而发生腐蚀。本体溶液pH值为酸性时缝内的化学环境变化迅速，缝口处发生腐蚀反应；而碱性条件下剥离区的pH值基本不变。本体溶液供氧量的减少降低了剥离区域内阴极保护的有效距离。外加电位的中断使缝内溶液酸化，X70钢处于自腐蚀状态。
A rectangle crevice assembly was used to study the crevice corrosion behaviors of X70 steels in Na2SO4 solutions under cathodic polarization condition. Effects of bulk solution concentration, pH, dissolved oxygen concentration on the electrochemical and chemical environments under the simulated disbanded coating were analyzed. It is shown that the higher bulk solution concentration was in favor of the cathodic current flowing into the crevice. However, the passivation film on the steel was attacked and corrosion occurred. The pH values of the solution under the disbonded coating with the alkaline bulk solution hardly changed while it changed rapidly with the acidic one and the steel at the opening was corroded. The available cathodic protection distance decreased with the dissolved oxygen being removed in bulk solution. The switching off of the applied potential led to the solution acidification and a free corrosion state of the X70 steel.
参考文献
| [1] | Chin D T, Sabde G M. Modeling transport process and current distribute in a cathodically protected crevice [J]. Corrosion, 2000, 56(8):783-793 [2]Song Y Q, Du C W, Li X G. Electrochemical corrosion behavior of carbon steel with bulk coating holidays [J]. J. Univ. Sci. Technol.Beijing （Miner. Metall. Mater.）, 2006, 13(2): 37-43[3] Puiggali M, Rousserie S, Touzet M. Fatigue crack initiation on low-carbon steel pipes in a near-neurtral-pH environment under potential control conditions [J]. Corrosion, 2002, 58(11):961-970[4] Sridhar N, Dunn D S, Seth M. Application of a general reactive transport model to predict environment under disbonded coating [J]. Corrosion, 2001, 57(7):598-613[5]Yan M C, Wang J Q， Ke W, et al. Effectiveness of cathodic protection under simulated disbonded coating on pipelines [J]. J. Chin.Soc. Corros. Prot., 2007, 27(5): 257-262[6] 闫茂成，王俭秋，柯伟等. 埋地管线剥离涂层覆盖下阴极保护的有效性 [J]. 中国腐蚀与防护学报, 2007, 27(5):257-262 [7] Li H L，Gao K W，Qiao L J，et al. Strength effect in stress corrosion cracking of high-strength steel in aqueous solution [J]. Corrosion, 2001, 57(4):295-299[8] Yan M C, Wang J Q, Han E H. Local environment under simulated disbonded coating on steel pipelines in soil solution [J]. Corros. Sci, 2008, 50(5):1331-1339[9] Li Z F, Gan F X, Mao X H. A study on cathodic protection against crevice corrosion in dilute NaCl solutions [J]. Corros. Sci, 2002, 44(4):689-701[10]Jack T R, Erno B, Krist K.Generation on near neutral pH and high pH SCC environments on buried pipelines [R]. Corrosion/2000, NACE International, Houston, TX, 2000: 211[11] Song F M, Kirk D W, Graydon J W, et al. Steel corrosion under a disbonded coating with a holiday-Part 1: The model and validation [J]. Corrosion, 2002, 58(12):1015-1024[12] Chen W，King F，Vokes E. Characteristics of near-neutral-pH stress corrosion cracks in an X65 pipeline [J]. Corrosion, 2002, 58(3):267-275[13] Parkins R N，Blanchard W K，Delanty B S. Transgranular stress corrosion cracking of high-pressure pipelines in contact with solution of near neutral [J]. Corrosion, 1994, 50(5):394-408[14] Gu B, Luo J, Mao X. Hydrogen-facilitated anodic dissolution-type stress corrosion cracking of pipeline steels in near-neutral pH solution [J]. Corrosion, 1999, 55(1):96-106[15]Liu X, Yang W. The susceptible environmental conditions of stress corrosion cracking of gas pipelines [J]．Mater. Mech. Eng., 2002, 26(1): 5-11[16](刘杏，杨武．天然气长输管线应力腐蚀破裂的敏感性条件 [J]．机械工程材料,2002, 26(1): 5-11)[17]Cao C N. The Environment Corrosion of Materials in China [M]. Beijing: Chemical Industry Press, 2005[18](曹楚南．中国材料的自然环境腐蚀 [M]．北京：化学工业出版社，2005)[19]Song F M, Jones D A, Kirk D W. Modeling pipeline corrosion within a disc-shaped crevice for various cathodic protection at the holiday and the effect of crevice geometry [R]. Corrosion /2005, Paper no.05137[20] Song F M, Jones D A, Kirk D W. Predicting corrosion and current flow within a disc crevice on coated steels [J]. Corrosion, 2005, 61(2):145-152[21] Gan F，Sun Z W，Sabde G，et al. Cathodic protection to mitigate external corrosion of underground steel pipe beneath disbonded coating [J]. Corrosion, 1994, 50(10):804-816[22]Yan M C, Weng Y J. High pH environment under coating on cathodic protection pipelines [J]. J. Chin. Soc. Corros. Prot.,2004, 24(2): 95-99[23] 闫茂成，翁永基. 阴极保护管线破损涂层下高pH环境形成规律 [J]. 中国腐蚀与防护学报, 2004, 24(2):95-99[24]Yan M C, Weng Y J. Effect of environmental solution on electrochemical behaviors related to SCC of pipe line steels [J]. J. Chin. Soc. Corros. Prot., 2005, 25(1): 34-38[25] 闫茂成，翁永基. 环境溶液对管道钢应力腐蚀过程电化学行为的影响 [J]. 中国腐蚀与防护学报, 2005, 25(1):34-38[26] Song F M, Sridhar N. Modeling pipeline crevice corrosion under a disbonded coating with or without cathodic protection under transient and steady state conditions [J]. Corros. Sci, 2008, 50(1):70-83[27]Cherry B W, Gould A N. Pitting corrosion of nominally protected land-based pipelines [J]. Mater. Perform., 1990, 29(8): 22-31[28] Brousseau R, Qian S. Distribution of steady-state current underneath a disbanded coatings [J]. Corrosion, 1994, 50(12):907-911[29] Perdomo J J, Chabica M E, Song I. Chemical and electrochemical conditions on steel under disbonded coatings: the effect of previously corrosion surface and wet and dry cycles [J]. Corros. Sci, 2001, 43(3):515-532 |
- 下载量()
- 访问量()
- 您的评分：
-
10%
-
20%
-
30%
-
40%
-
50%