本文關(guān)鍵詞：酸性氯化鈉溶液中硫脲基咪唑啉緩蝕劑對(duì)X70鋼孔蝕行為的影響　出處：《北京化工大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： X70鋼 孔蝕 硫脲 硫脲基咪唑啉

【摘要】：X70鋼在油氣田集輸系統(tǒng)中常處于酸性環(huán)境(pH 3～6),由于環(huán)境中含有Cl-等侵蝕性離子,X70鋼表面容易產(chǎn)生孔蝕,從而造成嚴(yán)重的經(jīng)濟(jì)損失。雖然相關(guān)學(xué)者針對(duì)該環(huán)境中使用的緩蝕劑進(jìn)行了部分研究,緩蝕劑的開發(fā)也比較成熟,但有機(jī)類緩蝕劑針對(duì)鋼材孔蝕的緩蝕機(jī)理仍不明確,需要進(jìn)一步的研究。為此,研究有機(jī)類緩蝕劑對(duì)酸性體系中X70鋼孔蝕的影響,可以進(jìn)一步揭示緩蝕機(jī)理,指導(dǎo)緩蝕劑的開發(fā)與實(shí)際應(yīng)用。本文采用了慢速動(dòng)電位掃描、電化學(xué)阻抗測(cè)試、Mott-Schottky曲線、掃描電鏡和能譜分析(SEM-EDS)和X射線光電子能譜(XPS)等方法研究在含0.2 mol/L NaCl+0.0mol/L NaNO2的體系(pH=5.5)中分別加入硫脲和硫脲基咪唑啉(TAI)后X70鋼的腐蝕行為,通過改變兩種緩蝕劑的濃度和浸泡時(shí)間等方法探討緩蝕劑對(duì)X70鋼小孔腐蝕的影響及緩蝕機(jī)理。通過對(duì)電化學(xué)參數(shù)(自腐蝕電流密度icorr、穩(wěn)定孔蝕電位Eb)分析,討論兩種緩蝕劑對(duì)X70鋼均勻腐蝕和孔蝕的緩蝕影響；通過Mott-Schottky、電化學(xué)阻抗譜、XPS等測(cè)試手段,對(duì)X70鋼在不同濃度的兩種緩蝕劑中、不同浸泡時(shí)間后表面吸附膜的形貌、元素成分和含量進(jìn)行分析,探討表面吸附膜層結(jié)構(gòu)以及膜層完整性等狀態(tài)變化的,研究兩種緩蝕劑對(duì)X70鋼孔蝕的緩蝕機(jī)理,主要得出以下結(jié)論：(1)X70鋼在0.2 mol/L NaCl+0.05 mol/L NaNO2的體系(pH=5.5)中添加適量(90～300 ppm)的硫脲作為緩蝕劑,硫脲可以抑制X70鋼的均勻腐蝕,但促進(jìn)孔蝕。體系中硫脲對(duì)X70鋼的緩蝕率隨著硫脲的加入量增大呈先增加后減小的趨勢(shì),當(dāng)加入量為90 ppm時(shí)緩蝕率最高。將X70鋼置于加入90 ppm硫脲緩蝕劑的體系中預(yù)鈍化24h,緩蝕率上升到98%。但硫脲在X70鋼表面形成的膜層結(jié)構(gòu)疏松,能夠促進(jìn)孔蝕的發(fā)生,在經(jīng)過浸泡和不浸泡兩種情況下硫脲緩蝕劑都會(huì)增大X70鋼的孔蝕敏感性,促進(jìn)孔蝕的發(fā)生。(2)X70鋼在0.2 mol/L NaCl+0.05 mol/L NaNO2的體系(pH=5.5)中,添加適量的硫脲基咪唑啉(TAI)緩蝕劑可以抑制均勻腐蝕,但促進(jìn)孔蝕的發(fā)生。當(dāng)TAI的添加濃度為40 ppm-110 ppm時(shí),TAI能夠促進(jìn)X70鋼的均勻腐蝕；添加濃度達(dá)到160 ppm時(shí)可以有效抑制均勻腐蝕,緩蝕率達(dá)到99%,自腐蝕電流密度降低4個(gè)數(shù)量級(jí),TAI可以促進(jìn)試樣表面膜層中的Fe2+轉(zhuǎn)化為Fe3+,可以有效抑制X70鋼均勻腐蝕；TAI濃度增大至240 ppm時(shí),,緩蝕率開始下降,緩蝕效果減弱�？孜g電位隨著咪唑啉用量的增加逐漸下降,是因?yàn)閄70鋼表面吸附膜疏松導(dǎo)致Cl-等侵蝕性離子侵入。(3)X70鋼在TAI中的浸泡時(shí)間對(duì)緩蝕效果有顯著影響,X70鋼在含Cl-酸性體系中加入160 ppm TAI,延長浸泡時(shí)間至24h,此時(shí)TAI針對(duì)X70鋼均勻腐蝕具有很好效果,同時(shí)也使X70鋼在體系中的孔蝕電位大幅上升,這是由于吸附膜可以有效阻隔Cl-的侵入,降低X70鋼的孔蝕敏感性耐孔蝕性,有效抑制孔蝕萌生。(4)X70鋼在TAI中浸泡24h后,膜層表面主要以咪唑啉分子為主；膜層中更深的位置硫脲分子含量增加,這是由于硫脲分子具有更小的相對(duì)分子質(zhì)量,優(yōu)先吸附在基體表面。硫脲分子為主的膜層結(jié)構(gòu)疏松,促進(jìn)孔蝕的發(fā)生；隨著浸泡時(shí)間的增加,咪唑啉分子包覆在硫脲分子之上,生成Fe-N配位鍵,形成致密的吸附膜,提高X70鋼在腐蝕介質(zhì)中的陽極活化能,降低陽極腐蝕速率；同時(shí),吸附膜外層的咪唑啉分子形成的疏水膜,可以有效阻隔侵蝕性離子的侵入,有效抑制均勻腐蝕和孔蝕。
[Abstract]:X70 steel in acidic environment and transportation system in oil and gas (pH 3 ~ 6), in the environment containing Cl- and other corrosive ions, the surface of X70 steel is prone to pitting, resulting in serious economic losses. Although scholars in the use of corrosion inhibitors in the environment are part of the research, development the inhibitor is mature, but the organic corrosion inhibitor for the corrosion mechanism of steel pitting are still not clear and need further research. Therefore, study on the effect of inhibitors on organic acid system in X70 steel pitting, can reveal the inhibition mechanism, guide the development and application of corrosion inhibitor agent. This paper uses the slow potentiodynamic scanning, electrochemical impedance test, Mott-Schottky curve, scanning electron microscopy and energy spectrum analysis (SEM-EDS) and X ray photoelectron spectroscopy (XPS) method in NaCl+0.0mol/L containing 0.2 mol/L NaNO2 system (pH=5.5) were added Thiourea and thiourea imidazoline (TAI) corrosion behavior of X70 steel after two, by changing the concentration of corrosion inhibitor and soaking time of corrosion inhibitors and inhibition mechanism of influence on the pitting corrosion of X70 steel. The electrochemical parameters (corrosion current density icorr, stable pitting potential Eb analysis) two, discuss the corrosion inhibition effect on X70 steel corrosion and pitting; by Mott-Schottky, electrochemical impedance spectroscopy, XPS spectroscopy of X70 steel in different concentrations of two kinds of corrosion inhibitors, the surface morphology of adsorption film after different immersion time, element composition and content analysis. To investigate the adsorption film structure and film integrity status change, on two kinds of corrosion inhibition mechanism of pitting corrosion of X70 steel, the main draw the following conclusions: (1) system of X70 steel in 0.2 mol/L NaCl+0.05 mol/L NaNO2 (pH=5.5) add amount (90 ~ 300 ppm) The thiourea as a corrosion inhibitor, thiourea can inhibit the uniform corrosion of X70 steel, but promotes pitting. In the system thiourea on X70 steel corrosion rate with thiourea added amount increased first and then decreases, when the dosage is 90 ppm. The highest inhibition rate of X70 steel in 90 ppm urea sulfur corrosion inhibitor system prepassive 24h inhibition rate rose to 98%. in the film but thiourea loose structure formed on the surface of X70 steel, can promote the occurrence of pitting, the pitting susceptibility after soaking and soaking in two cases of thiourea inhibitors will increase X70 steel, promote pitting happened. (2) system of X70 steel in 0.2 mol/L NaCl+0.05 mol/L NaNO2 (pH=5.5), adding proper amount of imidazoline (TAI) inhibitor can inhibit corrosion, but promote the occurrence of pitting. When the TAI concentration was 40 ppm-110 ppm, TAI can promote the corrosion of X70 steel Tim; And when the concentration reached 160 ppm can effectively inhibit the corrosion, the corrosion rate reached 99%, the corrosion current density decreased 4 orders, TAI can promote the film layer in the conversion of Fe2+ to Fe3+, can effectively inhibit the X70 steel uniform corrosion; the concentration of TAI increased to 240 ppm, and the inhibition rate began to decline and the inhibition effect was weakened. The pitting potential gradually decreased with increasing dosage of imidazoline because X70, adsorption film on the surface of Cl- steel lead to loose aggressive ion invasion. (3) soaking time of X70 steel in TAI has a significant effect on the inhibition effect of X70 steel with 160 ppm TAI in acid system with Cl- the immersion time, to 24h, the TAI for X70 steel corrosion has good effect, and the X70 steel pitting potential in the system increased sharply, this is because the adsorption film can effectively block the invasion of Cl-, reduce the X70 steel Kong Shimin emotional pitting resistance , effectively inhibit the pitting initiation. (4) X70 steel immersed in TAI 24h, the film surface mainly in the imidazoline molecule; increasing the molecular content in the film deeper position thiourea, this is due to the relative molecular mass of thiourea molecules with smaller, preferentially adsorbed on the surface of the substrate. The film structure of loose thiourea molecules mainly, promote occurrence of pitting; with the increase of immersion time, imidazoline molecule coated on the thiourea molecules on the formation of Fe-N coordination bond, forming dense membrane adsorption, improve the anode of X70 steel in corrosive medium activation energy, reduce the corrosion rate of anode; at the same time, the hydrophobic membrane imidazoline molecule adsorption film formed by the outer layer, can invade effectively the barrier of erosive ions, effectively inhibit the uniform corrosion and pitting corrosion.

【學(xué)位授予單位】：北京化工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG174.42

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 馬莉;王洪國;金鑫;廖克儉;;酸性緩蝕劑的研究進(jìn)展[J];當(dāng)代化工;2012年10期

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本文編號(hào)：1407932