李文濤,吳浩,王璇,苑旭雯,曹揚(yáng),楊懷玉
HCl介質(zhì)中二苯乙酮咪唑啉季銨鹽對(duì)碳鋼的緩蝕行為及機(jī)制
李文濤1,2,吳浩1,2,王璇1,苑旭雯1,2,曹揚(yáng)1,2,楊懷玉1
(1.中國(guó)科學(xué)院金屬研究所,沈陽(yáng) 110016;2.中國(guó)科學(xué)技術(shù)大學(xué) 材料科學(xué)與工程學(xué)院,合肥 230026)
合成一種二苯乙酮咪唑啉季銨鹽(PPLB)化合物,研究其在0.5 mol/L HCl溶液中對(duì)Q235鋼的緩蝕性能,探討其吸附動(dòng)力學(xué)過(guò)程及可能的緩蝕機(jī)制。以有機(jī)胺、硬脂酸、苯乙酮和氯化芐等為原料,經(jīng)脫水環(huán)化、曼尼希反應(yīng)和季銨化制備季銨鹽。通過(guò)腐蝕失重、動(dòng)電位極化曲線測(cè)試、電化學(xué)阻抗和表面形貌分析等手段,研究了二苯乙酮咪唑啉季銨鹽在HCl介質(zhì)中對(duì)Q235鋼的緩蝕性能。HCl溶液中PPLB對(duì)碳鋼具有優(yōu)異的緩蝕性能,緩蝕效率隨濃度和介質(zhì)溫度的升高而增加。在353 K下,PPLB添加量為4.8×10–4mol/L時(shí),緩蝕效率可達(dá)98.9%,表明緩蝕劑在高溫酸性介質(zhì)中仍可有效抑制碳鋼的腐蝕。電化學(xué)研究結(jié)果證明,PPLB可同時(shí)降低陰陽(yáng)極的腐蝕電流密度,即抑制了腐蝕的陰陽(yáng)極過(guò)程,是一種通過(guò)“幾何覆蓋效應(yīng)”起作用的混合型緩蝕劑,其在碳鋼表面的吸附遵循Langmuir吸附等溫規(guī)律,為典型的化學(xué)吸附。合成的二苯乙酮咪唑啉季銨鹽化合物是一種優(yōu)異的酸性介質(zhì)緩蝕劑,獨(dú)特的分子結(jié)構(gòu)使其通過(guò)多中心化學(xué)吸附在碳鋼表面生成保護(hù)性吸附膜,從而有效抑制了HCl對(duì)碳鋼的腐蝕。
緩蝕劑;季銨鹽;碳鋼;電化學(xué);吸附;酸液腐蝕
近年來(lái),隨著生產(chǎn)開(kāi)發(fā)的不斷深入,油氣井產(chǎn)出液中水含量逐漸增加,油氣產(chǎn)量不斷下降。酸化壓裂已成為增加油氣產(chǎn)能、提高采收率、實(shí)現(xiàn)油氣穩(wěn)產(chǎn)和增產(chǎn)最普遍的技術(shù)手段,尤其是在當(dāng)前我國(guó)油氣供應(yīng)對(duì)外依存度不斷攀升的形勢(shì)下,如何保證酸化壓裂等增產(chǎn)技術(shù)措施地順利實(shí)施,顯得愈發(fā)重要。除此之外,許多化工過(guò)程,如酸洗、除銹、除垢和化學(xué)合成等,都需要使用無(wú)機(jī)或有機(jī)酸液,因其具有強(qiáng)烈的腐蝕性,將不可避免地對(duì)相關(guān)金屬設(shè)備和裝置造成嚴(yán)重腐蝕,不僅大幅縮短了設(shè)備的使用壽命,造成重大經(jīng)濟(jì)損失,甚至還可能引發(fā)嚴(yán)重的安全生產(chǎn)事故[1-2]。有許多手段可用來(lái)減緩酸性介質(zhì)中金屬設(shè)備的腐蝕,其中添加緩蝕劑因其成本低、可操作性強(qiáng)、保護(hù)效果好、適用范圍廣等特點(diǎn),在石油、冶金、機(jī)械、能源、交通運(yùn)輸和國(guó)防工業(yè)等領(lǐng)域發(fā)揮著重要的防腐作用,已成為應(yīng)用最廣泛的腐蝕防護(hù)技術(shù)之一[3]。酸性緩蝕劑通常是由含碳?xì)湓臃菢O性基團(tuán)和含氮、氧、硫、磷等電負(fù)性較大的雜原子極性基團(tuán)組成,這些有機(jī)化合物分子通過(guò)與金屬表面間的靜電相互作用、共享電子或活性位點(diǎn)吸附等方式,在金屬表面形成一層保護(hù)性吸附膜,有效阻礙侵蝕性物質(zhì)與金屬表面接觸,從而達(dá)到減緩金屬腐蝕的目的。有機(jī)化合物在金屬表面的吸附不僅取決于化合物的物理和化學(xué)性質(zhì),還與其分子中官能團(tuán)、電子云密度、芳香性、空間位阻效應(yīng)和π電子特性等密切相關(guān)[4-5]。
咪唑啉及其季銨鹽作為一種優(yōu)良的緩蝕劑,因其獨(dú)特的分子結(jié)構(gòu),以及低成本、高效、易合成和良好的生物降解性等特點(diǎn),在多種無(wú)機(jī)、有機(jī)酸中,對(duì)碳鋼、鐵基合金、銅和鋁及其合金等均具有較好的緩蝕效果[6-8],目前已廣泛應(yīng)用于石油天然氣生產(chǎn)、集輸和儲(chǔ)運(yùn)中的腐蝕防護(hù)過(guò)程[9-10]。因此,多年來(lái)有關(guān)咪唑啉及其衍生物緩蝕效果及緩蝕機(jī)理的研究,一直是國(guó)內(nèi)外緩蝕劑領(lǐng)域的一個(gè)熱點(diǎn)。近期,Kegui Zhang等[11]研究了不同鹵代咪唑啉衍生物在0.5 mol/L HCl溶液中對(duì)Q235鋼的緩蝕性能,發(fā)現(xiàn)氯代咪唑啉分子因更傾向于在鐵晶面發(fā)生平行式吸附,并形成更致密的吸附膜,其緩蝕性能明顯優(yōu)于氟代咪唑啉。Jun Zhang等[12]通過(guò)量化計(jì)算和分子動(dòng)力學(xué)模擬,系統(tǒng)研究了4種不同親水基團(tuán)的十一烷基咪唑啉化合物在3% NaCl飽和CO2溶液中對(duì)碳鋼的緩蝕效果,結(jié)果表明,4種咪唑啉衍生物分子均可在鐵表面形成自組裝膜,且親水基團(tuán)對(duì)咪唑啉分子的反應(yīng)活性、自組裝膜與鐵表面間結(jié)合強(qiáng)度,以及自組裝膜的致密性具有明顯的影響,其緩蝕性能優(yōu)劣順序?yàn)椤猂==CH2COOH > —CH2CH2OH >—CH2CH2NH2> H。此外,曼尼希堿類緩蝕劑始終受到人們的廣泛關(guān)注。曼尼希堿是一類由醛或酮的α-活潑氫與醛和胺發(fā)生縮合反應(yīng)(曼尼希反應(yīng))得到的β-氨基化合物,與其他酸性緩蝕劑相比,它具有結(jié)構(gòu)穩(wěn)定、緩蝕效果好、耐高溫等特點(diǎn)[13-18]。然而,盡管人們對(duì)上述兩類化合物的緩蝕性能及緩蝕機(jī)理進(jìn)行了大量研究,但目前為止,就其具體分子中吸附活性位點(diǎn)的確定,以及對(duì)緩蝕機(jī)理的深入理解仍存在很大爭(zhēng)議,有待進(jìn)一步研究。另外,有關(guān)曼尼希堿式咪唑啉季銨鹽作為緩蝕劑的研究也未見(jiàn)報(bào)道。
為此,本文以有機(jī)胺、硬脂酸等為原料,經(jīng)脫水環(huán)化與曼尼希反應(yīng)等過(guò)程,制備了一種兼具咪唑啉和曼尼希堿類緩蝕劑特征的二苯乙酮咪唑啉季銨鹽,其目的是通過(guò)腐蝕失重和電化學(xué)等手段,研究該化合物在0.5 mol/L HCl溶液中對(duì)碳鋼的緩蝕性能,并結(jié)合吸附動(dòng)力學(xué)行為和相關(guān)動(dòng)力/熱力學(xué)參數(shù),分析探討其可能的緩蝕作用機(jī)理,以期為該類緩蝕劑工業(yè)應(yīng)用提供可靠技術(shù)支撐。
實(shí)驗(yàn)材料為Q235鋼,其化學(xué)組成(質(zhì)量分?jǐn)?shù))為:C 0.15%,Mn 0.06%,P 0.55%,Si 0.01%,余量Fe。所用試劑為三乙烯四胺、硬脂酸、苯乙酮、甲醛和氯化芐,上述試劑均為分析純,購(gòu)自國(guó)藥集團(tuán)化學(xué)試劑有限公司。腐蝕介質(zhì)為0.5 mol/L HCl溶液,由蒸餾水和37% HCl配制而成。
將三乙烯四胺和硬脂酸按物質(zhì)的量比1∶1混合,放入裝有機(jī)械攪拌和分水器的三口燒瓶中,通入氮?dú)獠⒓訜嶂?33 K,在攪拌條件下反應(yīng)3 h,而后繼續(xù)加熱至493 K反應(yīng)4 h,所得產(chǎn)物標(biāo)記為P1。將P1與苯乙酮和甲醛按物質(zhì)的量比1∶2∶2混合,加熱至358 K并攪拌反應(yīng)4 h,經(jīng)曼尼希反應(yīng)后,所得產(chǎn)物標(biāo)記為P2。最后將P2與氯化芐混合物加熱至353 K回流反應(yīng)36 h,得到目標(biāo)產(chǎn)物PPLB,其分子結(jié)構(gòu)如圖1所示。
圖2為化合物PPLB的紅外光譜。由圖2可知,1647 cm–1處為C==N伸縮振動(dòng)峰,為咪唑環(huán)的特征吸收峰,3062 cm–1處為咪唑環(huán)上C—H伸縮振動(dòng),1551 cm–1處為C—H彎曲振動(dòng)峰,1456 cm–1處為—CH3彎曲振動(dòng)峰,2854 cm–1和2926 cm–1處為—CH2伸縮振動(dòng)峰,1743 cm–1處為—C==O伸縮振動(dòng)峰。上述紅外結(jié)果表明,所制備產(chǎn)物為目標(biāo)化合物[19-23]。
圖1 PPLB分子結(jié)構(gòu)
圖2 PPLB的紅外光譜
失重試片由Q235鋼板材經(jīng)線切割后加工而成,尺寸為50 mm×25 mm×2 mm。所有試片表面依次經(jīng)200、400、800目砂紙逐級(jí)打磨,蒸餾水和丙酮清洗,冷風(fēng)吹干后儲(chǔ)存于真空干燥器。將準(zhǔn)確稱量后的試樣放入含有不同濃度緩蝕劑的500 ml 0.5 mol/L HCl溶液中,浸泡4 h后取出,小心去除表面腐蝕產(chǎn)物,并依次用蒸餾水和乙醇清洗,干燥后再次稱量。為保證實(shí)驗(yàn)數(shù)據(jù)的重現(xiàn)性,每組實(shí)驗(yàn)采用3個(gè)平行樣同時(shí)進(jìn)行,失重結(jié)果取平均值。實(shí)驗(yàn)分別在293、313、333、353 K下進(jìn)行。失重實(shí)驗(yàn)的腐蝕速率()由式(1)計(jì)算。
式中:1和2分別為失重實(shí)驗(yàn)前后試片的質(zhì)量,為試片面積,為腐蝕時(shí)間。緩蝕效率和覆蓋度可分別由式(2)和(3)計(jì)算[24]。
式中:0和1分別為空白和添加緩蝕劑時(shí)試片的腐蝕速率。
所有電化學(xué)實(shí)驗(yàn)均在Parstat 2273電化學(xué)工作站上進(jìn)行,采用標(biāo)準(zhǔn)三電極電解池,輔助電極為大面積鉑片(Pt),參比電極為飽和甘汞(SCE)電極,工作電極為Q235鋼。除0.785 cm2工作面外,電極其余部分用環(huán)氧樹(shù)脂密封在聚四氟乙烯管中。實(shí)驗(yàn)前,工作面用SiC砂紙逐級(jí)打磨至800目,蒸餾水與丙酮清洗后冷風(fēng)吹干。為獲得穩(wěn)定的開(kāi)路電位(OCP),將工作電極放入待測(cè)溶液1 h后開(kāi)始電化學(xué)測(cè)量。
動(dòng)電位極化曲線的測(cè)量電位范圍為相對(duì)OCP ?150 ~ +350 mV,電位掃描速度為0.5 mV/s,實(shí)驗(yàn)數(shù)據(jù)通過(guò)Powersuite軟件進(jìn)行分析。電化學(xué)交流阻抗測(cè)量在OCP下進(jìn)行,頻率范圍為100 kHz~10 mHz,激勵(lì)信號(hào)為振幅±10 mV交流信號(hào),實(shí)驗(yàn)數(shù)據(jù)用Zsmipwin軟件進(jìn)行擬合。
將Q235鋼制成10 mm×10 mm×2 mm試樣并逐級(jí)打磨至2000目,用Al2O3研磨膏拋光,蒸餾水和丙酮清洗后,分別浸泡于空白和添加4.8×10–4mol/L PPLB的0.5 mol/L HCl溶液中,4 h后取出,蒸餾水清洗,冷風(fēng)吹干后,用ESEM XL30 FEG掃描電子顯微鏡觀察試樣表面。
不同溫度條件下,碳鋼在添加不同濃度PPLB的0.5 mol/L HCl溶液中的腐蝕速率及相應(yīng)緩蝕效率列于表1。從表1可以看出,PPLB在0.5 mol/L HCl溶液中對(duì)Q235鋼具有優(yōu)異的緩蝕性能。在293 K,添加濃度僅為1.5×10–6mol/L時(shí),緩蝕效率高達(dá)93.3%,且在整個(gè)實(shí)驗(yàn)濃度范圍內(nèi),緩蝕效率隨緩蝕劑濃度的增加而逐漸升高,當(dāng)添加濃度為4.8× 10–4mol/L時(shí),緩蝕率達(dá)到97.2%。在其他溫度條件下,緩蝕效率隨緩蝕劑濃度的升高也具有類似的變化規(guī)律。這可能是由PPLB分子結(jié)構(gòu)中N和O原子通過(guò)其孤對(duì)電子與Fe原子空d軌道形成配位鍵所致。此外,化合物分子結(jié)構(gòu)中的C==O和C==N上的π電子也可與金屬空d軌道進(jìn)行鍵合,即緩蝕劑分子在金屬表面發(fā)生化學(xué)吸附[25]。另外,隨緩蝕劑濃度的增加,緩蝕劑分子在碳鋼表面的吸附速率加快,吸附量增大,覆蓋度不斷增加,表明緩蝕劑分子在碳鋼表面形成穩(wěn)定的吸附保護(hù)膜,阻止了酸性介質(zhì)中的H+與金屬表面接觸,從而有效抑制了金屬腐蝕,緩蝕效率進(jìn)一步提高。對(duì)表1結(jié)果需要注意的是,在353 K時(shí),當(dāng)緩蝕劑濃度為1.5×10–6mol/L時(shí),與低溫時(shí)相比,緩蝕效率降至82%。這是因?yàn)?,一方面溫度升高加速了緩蝕劑分子的熱運(yùn)動(dòng)及在溶液中的擴(kuò)散,弱化了緩蝕劑分子與金屬表面間的作用[26];另一方面,介質(zhì)溫度升高還可致使腐蝕加劇,此時(shí)無(wú)論陽(yáng)極鐵的溶解還是陰極氫的析出,都將不利于緩蝕劑分子的吸附。因此,在高溫下,低緩蝕劑濃度(1.5×10–6mol/L)時(shí),緩蝕劑無(wú)法在碳鋼表面形成致密完整的吸附膜,致使緩蝕效率有所下降。但當(dāng)緩蝕劑濃度增加至4.8× 10–4mol/L時(shí),緩蝕率增至98.9%,表明緩蝕劑添加量達(dá)到一定濃度時(shí),高溫下該化合物仍具有優(yōu)異的緩蝕性能。
此外,對(duì)表1結(jié)果仔細(xì)分析還可以發(fā)現(xiàn),當(dāng)緩蝕劑濃度低于3.0×10–5mol/L時(shí),緩蝕效率隨濃度的增加而明顯升高,且隨酸液溫度的升高,緩蝕效率的提升幅度更大;但當(dāng)緩蝕劑濃度高于3.0×10–5mol/L時(shí),這種升高的趨勢(shì)開(kāi)始減緩,表明PPLB分子在碳鋼表面的吸附隨其濃度的增加而逐漸趨于飽和。通常情況下,升高溫度不僅會(huì)加速金屬在酸性溶液中的溶解,還會(huì)促進(jìn)緩蝕劑在金屬表面脫附,導(dǎo)致緩蝕效率下降。PPLB對(duì)碳鋼的緩蝕效率隨溫度的升高而增大,這意味著緩蝕劑分子與碳鋼表面間的相互作用并非單一的物理作用,可能存在強(qiáng)烈的化學(xué)吸附。這里需要指出的是,雖然緩蝕效率隨溫度的升高而增大,但與低溫時(shí)相比,相同緩蝕劑濃度下,碳鋼的絕對(duì)腐蝕速率有所升高,這主要是由空白溶液中碳鋼的絕對(duì)腐蝕速率隨溫度升高而快速增加所致。
表1 不同溫度下Q235鋼在不同濃度PPLB的0.5 mol/L HCl溶液中的失重結(jié)果
Tab.1 Corrosion rate and inhibition efficiency obtained from weight loss measurements for Q235 steel in 0.5 mol/L HCl solution with various concentration of PPLB at different temperatures
圖3為293 K時(shí),碳鋼在添加不同濃度緩蝕劑的0.5 mol/L HCl溶液中的動(dòng)電位極化曲線。通過(guò)外推法擬合得到的腐蝕電位(corr)、腐蝕電流密度(corr)等電化學(xué)參數(shù)列于表2。其中,緩蝕效率由式(4)計(jì)算[27]。
從圖3可以看出,隨緩蝕劑濃度的增加,碳鋼陰陽(yáng)極極化曲線逐漸向低腐蝕電流密度方向移動(dòng),尤其是在低濃度時(shí),這種趨勢(shì)更明顯,表明緩蝕劑的添加對(duì)陽(yáng)極鐵的溶解和陰極氫的析出過(guò)程均具有很好的抑制作用,且隨緩蝕劑濃度的增加,上述抑制作用越來(lái)越強(qiáng)。另外,在掃描電位范圍內(nèi),隨緩蝕劑濃度的改變,陰極支極化曲線基本呈平行狀態(tài),說(shuō)明緩蝕劑加入并沒(méi)有改變電極過(guò)程的陰極析氫機(jī)理[28]。至于極化的陽(yáng)極支,當(dāng)極化電位在自腐蝕電位至–300 mV區(qū)間時(shí),隨緩蝕劑濃度的增加,陽(yáng)極corr逐步減小,緩蝕劑表現(xiàn)出優(yōu)良的陽(yáng)極抑制特性。但當(dāng)極化電位高于–300 mV時(shí),隨電位的增加,陽(yáng)極corr出現(xiàn)一個(gè)快速增加的“平臺(tái)”區(qū),尤其在高濃度時(shí),這一過(guò)程尤為突出。這是因?yàn)殡S陽(yáng)極極化電位的升高,鐵的陽(yáng)極溶解速度加快,被緩蝕劑覆蓋的電極表面不再穩(wěn)定,緩蝕劑分子在碳鋼表面的吸/脫附平衡被打破,吸附緩蝕劑分子在自身熱運(yùn)動(dòng)和鐵陽(yáng)極溶解的攜帶作用下開(kāi)始離開(kāi)碳鋼表面,導(dǎo)致已吸附在電極表面上的緩蝕劑分子發(fā)生陽(yáng)極脫附,這也是吸附型緩蝕劑在陽(yáng)極極化電位較高時(shí)的突出特征。通常把與該“電流平臺(tái)”對(duì)應(yīng)的電位稱作緩蝕劑的陽(yáng)極脫附電位,陽(yáng)極脫附電位越高,表明緩蝕劑吸附越穩(wěn)定[29-31]。由圖3可知,隨緩蝕劑濃度的增加,緩蝕劑脫附電位逐漸升高,這表明隨PPLB濃度的升高,其在碳鋼表面的吸附越穩(wěn)定[32]。
圖3 Q235鋼在添加不同濃度PPLB的0.5 mol/L HCl溶液中的極化曲線
由表2結(jié)果可以看出,添加PPLB后,碳鋼的corr顯著降低,當(dāng)添加濃度為4.8×10–4mol/L時(shí),corr值由1518 μA/cm2降至13 μA/cm2,緩蝕率高達(dá)99.1%,且隨緩蝕劑濃度的增大,碳鋼腐蝕電流密度逐漸下降,表明緩蝕劑對(duì)HCl溶液中碳鋼的腐蝕具有優(yōu)良的抑制性能。另外,與空白相比,添加緩蝕劑后碳鋼的corr沒(méi)有發(fā)生明顯變化(Δcorr< 85 mV),且腐蝕反應(yīng)的陰陽(yáng)極Tafel斜率變化不大,表明PPLB緩蝕劑為混合型緩蝕劑,其在碳鋼表面的吸附為幾何覆蓋效應(yīng),緩蝕劑添加并沒(méi)有改變碳鋼在HCl介質(zhì)中的腐蝕機(jī)理[33-34]。
表2 Q235鋼在添加不同濃度PPLB的0.5 mol/L HCl溶液中的動(dòng)電位極化曲線擬合參數(shù)
Tab.2 Electrochemical parameters obtained from poten-tio--dynamic polarization curve for Q235 steel in 0.5 mol/L HCl solutions with different concentrations of PPLB
圖4為293 K時(shí),碳鋼在添加不同濃度PPLB的0.5 mol/L HCl溶液中的Nyquist和 Bode阻抗圖譜。可以看出,隨PPLB添加濃度不斷增加,無(wú)論Nyquist 圖中(圖4a)的容抗弧半徑,還是Bode圖中(圖4b)的低頻阻抗膜值和最大相位角均逐漸增大,尤其在緩蝕劑濃度較低時(shí),這種變化幅度和趨勢(shì)更為顯著,說(shuō)明緩蝕劑的加入,有效提高了碳鋼電極表面的腐蝕反應(yīng)阻力,且隨其濃度的增加,緩蝕劑分子在碳鋼電極表面的吸附逐漸增強(qiáng),吸附量不斷增加,所形成的保護(hù)性吸附膜越來(lái)越完整致密,從而有效地減緩了Q235鋼在酸性溶液中的腐蝕,對(duì)碳鋼起到明顯的抑制作用。另外還可發(fā)現(xiàn),Nyquist圖由高中頻和低頻2個(gè)容抗弧構(gòu)成,且在與此相應(yīng)的Bode圖中,隨緩蝕劑濃度的增加,相位角也逐漸分化出兩個(gè)清晰可見(jiàn)的最大相位角峰,表明該體系存在兩個(gè)時(shí)間常數(shù)。其中高頻端時(shí)間常數(shù)對(duì)應(yīng)于電極表面法拉第過(guò)程,即電荷轉(zhuǎn)移電阻與雙電層電容對(duì)交流信號(hào)的響應(yīng),而低頻端時(shí)間常數(shù)則為碳鋼表面吸附粒子的弛豫過(guò)程[35-36]。此外,在阻抗復(fù)平面中的容抗弧呈現(xiàn)為圓心偏下的不完整半圓狀,這種現(xiàn)象通常被認(rèn)為是由電極表面的不均勻性和電場(chǎng)分布不均而產(chǎn)生的彌散效應(yīng)所致[37]。
基于上述阻抗行為的變化規(guī)律及分析,采用圖5所示等效電路對(duì)阻抗數(shù)據(jù)進(jìn)行擬合(圖5a、b分別用于擬合空白和添加緩蝕劑后的阻抗數(shù)據(jù)),其中s為溶液電阻,ct為電荷轉(zhuǎn)移電阻,f為緩蝕劑等物種吸附膜電阻,CPE1和CPE2分別代表雙電層電容和緩蝕劑等粒子吸附膜電容,為表征電極表面不均勻程度的參數(shù),擬合所得電化學(xué)參數(shù)列于表3。在電化學(xué)阻抗實(shí)驗(yàn)中,緩蝕效率通過(guò)公式(5)進(jìn)行計(jì)算[38-39]。
圖4 添加不同濃度緩蝕劑時(shí)Q235鋼電極在0.5 mol/L HCl溶液中的Nyquist圖和Bode圖
圖5 電化學(xué)阻抗擬合等效電路
Fig.5 Equivalent circuit model used to fit EIS data: (a) blank; (b) with PPLB
表3 Q235鋼在添加不同濃度PPLB的0.5 mol/L HCl溶液中的電化學(xué)阻抗擬合參數(shù)
Tab.3 Impedance parameters derived from EIS data for Q235 steel in 0.5 mol/L HCl in the absence and the presence of different concentrations of PPLB
吸附等溫式可反映緩蝕劑分子與碳鋼表面間相互作用的本質(zhì),通過(guò)對(duì)不同吸附等溫式進(jìn)行擬合,發(fā)現(xiàn)Langmuir吸附等溫式擬合結(jié)果最佳,其斜率趨近于1。式(6)為L(zhǎng)angmuir吸附等溫式[42]。
圖6 不同溫度下PPLB在Q235鋼表面的吸附Langmuir擬合結(jié)果
表4 不同溫度下PPLB在Q235鋼表面吸附熱力學(xué)參數(shù)
Tab.4 Adsorption parameters obtained from weight loss measurements for PPLB inhibitor at different temperatures
圖7 PPLB分子在Q235鋼表面吸附示意圖
假定Q235鋼在0.5 mol/L HCl溶液中的腐蝕速率和溫度之間滿足Arrhenius公式(8)及其變換式(9)[47]。
式中:為表觀活化能,為指前因子,為摩爾氣體常數(shù),為阿伏伽德羅常數(shù),為普朗克常量,?a和?a分別為反應(yīng)的活化焓和活化熵。圖8為ln以及l(fā)n(/)與1/間的關(guān)系圖。根據(jù)線性擬合結(jié)果分別計(jì)算得到的、?a和?a值列于表5。由表5可知,添加緩蝕劑后,活化能明顯下降,說(shuō)明添加緩蝕劑后,金屬表面能壘降低,與緩蝕劑分子間的反應(yīng)活性隨之增大,緩蝕劑更易吸附在金屬表面。而空白溶液中,?a為正值,表明碳鋼在酸性溶液中的溶解為吸熱過(guò)程,溫度升高可促進(jìn)碳鋼腐蝕,這與腐蝕失重實(shí)驗(yàn)結(jié)果相一致。與空白溶液時(shí)相比,添加緩蝕劑后,?a明顯降低,表明碳鋼表面生成的吸附保護(hù)膜可有效抑制金屬的陽(yáng)極溶解。另外,添加緩蝕劑后,與空白相比,?a值更負(fù),表明緩蝕劑吸附是一個(gè)熵減過(guò)程,這是因?yàn)樘砑泳徫g劑后,緩蝕劑分子逐漸由溶液中的無(wú)序狀態(tài)轉(zhuǎn)化為在碳鋼表面有規(guī)則吸附的有序狀態(tài),導(dǎo)致體系混亂度減小,活化熵降低[48-49]。
圖8 空白和添加PPLB時(shí)Q235鋼的lnr以及l(fā)n(r/T)與1/T間的關(guān)系
表5 空白和添加PPLB時(shí)Q235鋼表面腐蝕過(guò)程動(dòng)力學(xué)參數(shù)
Tab.5 The calculated kinetic parameters from weight loss measurements for Q235 steel in 0.5 mol/L HCl solutions without and with PPLB of 4.8×10–4 mol/L
圖9為293 K時(shí),Q235鋼在空白和添加4.8× 10–4mol/L PPLB的0.5 mol/L HCl溶液中浸泡4 h后的表面形貌。由圖9可以看出,在空白HCl溶液中(圖9b),試片表面遭受嚴(yán)重腐蝕,表面粗糙度明顯增加。而在添加緩蝕劑的酸液中(圖9c),試樣經(jīng)4 h腐蝕后,表面依舊光滑均勻,腐蝕程度顯著下降,這表明PPLB對(duì)HCl溶液中Q235鋼的腐蝕具有優(yōu)異的抑制效果。
圖9 Q235鋼表面的SEM形貌
1)合成的二苯乙酮咪唑啉季銨鹽對(duì)Q235鋼在0.5 mol/L HCl溶液中的腐蝕具有優(yōu)異的緩蝕性能,緩蝕效率隨其濃度和介質(zhì)溫度的升高而增加。
2)電化學(xué)研究結(jié)果表明,隨緩蝕劑濃度的增加,Q235鋼的腐蝕電流密度與雙電層電容逐漸下降,但其電荷轉(zhuǎn)移電阻和吸附膜電阻隨濃度的升高而逐漸增大。PPLB可同時(shí)抑制腐蝕的陰、陽(yáng)極過(guò)程,為具有“幾何覆蓋效應(yīng)”的混合型緩蝕劑。失重與電化學(xué)研究結(jié)果具有很好的一致性。
3)PPLB化合物在碳鋼表面的吸附符合Langmuir吸附等溫規(guī)律,吸附為自發(fā)的化學(xué)過(guò)程,添加緩蝕劑后,吸附反應(yīng)的活化能、活化焓和活化熵降低,表明溫度升高有利于化合物在碳鋼表面形成致密有序的吸附保護(hù)膜。
[1] FIN?GAR M, JACKSON J. Application of Corrosion Inhibitors for Steels in Acidic Media for the Oil and Gas Industry: A Review[J]. Corrosion Science, 2014, 86: 17- 41.
[2] HOOSHMAND ZAFERANI S, SHARIFI M, ZAAREI D, et al. Application of Eco-Friendly Products as Corro-sion Inhibitors for Metals in Acid Pickling Processes: a Review[J]. Journal of Environmental Chemical Enginee-ring, 2013, 1(4): 652-657.
[3] UMOREN S A, SOLOMON M M. Effect of Halide Ions on the Corrosion Inhibition Efficiency of Different Or-ganic Species: a Review[J]. Journal of Industrial and Engineering Chemistry, 2015, 21: 81-100.
[4] GOYAL M, KUMAR S, BAHADUR I, et al. Organic Corrosion Inhibitors for Industrial Cleaning of Ferrous and Non-Ferrous Metals in Acidic Solutions: A Re-view[J]. Journal of Molecular Liquids, 2018, 256: 565- 573.
[5] ITUEN E, AKARANTA O, JAMES A. Evaluation of Performance of Corrosion Inhibitors Using Adsorption Isotherm Models: An Overview[J]. Chemical Science International Journal, 2017, 18(1): 1-34.
[6] GONZáLEZ-RODRíGUEZ C A, RODRíGUEZ-Gó-ME-Z F J, GENESCá-LLONGUERAS J. The Influen-ce of Desulfovibrio Vulgaris on the Efficiency of Imi-dazo-line as a Corrosion Inhibitor on Low-Carbon Steel in Sea-water[J]. Electrochimica Acta, 2008, 54(1): 86-90.
[7] OKAFOR P C, ZHENG Yu-gui. Synergistic Inhibition Behaviour of Methylbenzyl Quaternary Imidazoline Deri-va-tive and Iodide Ions on Mild Steel in H2SO4Solu-tions[J]. Corrosion Science, 2009, 51(4): 850-859.
[8] FARELAS F, RAMIREZ A. Carbon Dioxide Corrosion Inhibition of Carbon Steels through Bis-Imidazoline and Imidazoline Compounds Studied by EIS[J]. International Journal of Electrochemical Science, 2010, 5(6): 797-814.
[9] JEVREMOVI? I, SINGER M, NE?I? S, et al. Inhibition Properties of Self-Assembled Corrosion Inhibitor Talloil Diethylenetriamine Imidazoline for Mild Steel Corrosion in Chloride Solution Saturated with Carbon Dioxide[J]. Corrosion Science, 2013, 77: 265-272.
[10] SHAMSA A, BARKER R, HUA Yong, et al. Perfor-mance Evaluation of an Imidazoline Corrosion Inhibitor in a CO2-Saturated Environment with Emphasis on Loca-lised Corrosion[J]. Corrosion Science, 2020, 176: 108916.
[11] ZHANG Ke-gui, XU Bin, YANG Wen-zhong, et al. Halogen-Substituted Imidazoline Derivatives as Corro-sion Inhibitors for Mild Steel in Hydrochloric Acid Solu-tion[J]. Corrosion Science, 2015, 90: 284-295.
[12] ZHANG Jun, QIAO Gui-min, HU Song-qing, et al. Theoretical Evaluation of Corrosion Inhibition Perfor-man-ce of Imidazoline Compounds with Different Hydro-philic Groups[J]. Corrosion Science, 2011, 53(1): 147- 152.
[13] AHAMAD I, PRASAD R, QURAISHI M A. Adsorption and Inhibitive Properties of some New Mannich Bases of Isatin Derivatives on Corrosion of Mild Steel in Acidic Media[J]. Corrosion Science, 2010, 52(4): 1472-1481.
[14] TANG Ming-jin, LI Jian-bo, LI Zhi-da, et al. Mannich Base as Corrosion Inhibitors for N80 Steel in a CO2Saturated Solution Containing 3wt% NaCl[J]. Materials, 2019, 12(3): 449.
[15] QURAISHI M A, AHAMAD I, SINGH A K, et al. N-(Piperidinomethyl)-3-[(Pyridylidene)Amino] Isatin: A New and Effective Acid Corrosion Inhibitor for Mild Steel[J]. Materials Chemistry and Physics, 2008, 112(3): 1035-1039.
[16] VERMA C, QURAISHI M, EBENSO E. Mannich Bases Derived from Melamine, Formaldehyde Alkanoleamines as Novel Corrosion Inhibitors for Mild Steel in Hy-drochloric Acid Medium[J]. International Journal of Electrochemical Science, 2013, 8(8): 10851-10863.
[17] YADAV M, SHARMA U, YADAV P. Corrosion Inhi-bitive Properties of some New Isatin Derivatives on Corrosion of N80 Steel in 15% HCl[J]. International Journal of Industrial Chemistry, 2020, 11(3): 203.
[18] JEEVA M, VENKATESA PRABHU G, RAJESH C M. Inhibition Effect of Nicotinamide and Its Mannich Base Derivatives on Mild Steel Corrosion in HCl[J]. Journal of Materials Science, 2017, 52(21): 12861-12888.
[19] FARAHATI R, GHAFFARINEJAD A, MOUSAVI- KHOSHDEL S M, et al. Synthesis and Potential App-lications of some Thiazoles as Corrosion Inhibitor of Copper in 1 M HCl: Experimental and Theoretical Studi-es[J]. Progress in Organic Coatings, 2019, 132: 417- 428.
[20] MIGAHED M A, RASHWAN S M, KAMEL M M, et al. Synthesis, Characterization of Polyaspartic Acid-Glycine Adduct and Evaluation of Their Performance as Scale and Corrosion Inhibitor in Desalination Water Plants[J]. Jour-nal of Molecular Liquids, 2016, 224: 849-858.
[21] FENG Li-juan, YANG Huai-yu, WANG Fu-hui. Experi-mental and Theoretical Studies for Corrosion Inhi-bition of Carbon Steel by Imidazoline Derivative in 5% NaCl Satura-ted Ca(OH)2Solution[J]. Electrochimica Acta, 2011, 58: 427-436.
[22] 張晨峰, 扈俊穎, 鐘顯康, 等. 雙咪唑啉在CO2/O2環(huán)境中的緩蝕行為及其與巰基乙醇的復(fù)配性能[J]. 表面技術(shù), 2020, 49(11): 66-74.
ZHANG Chen-feng, HU Jun-ying, ZHONG Xian-kang, et al. Bis-Imidazoline Compound as a Corrosion Inhibitor in CO2/O2Environment and Its Synergistic Effect with 2-Mercaptoethanol[J]. Surface Technology, 2020, 49(11): 66-74.
[23] 饒興興, 王璇, 王言建, 等. 環(huán)境友好型含辣椒素締合物的緩蝕性能評(píng)價(jià)[J]. 表面技術(shù), 2020, 49(11): 252-261.
RAO Xing-xing, WANG Xuan, WANG Yan-jian, et al. Cor-ro-sion Inhibition Evaluation of Environmentally Frien---dly Capsaicin-Containing Associations[J]. Surface Tech-nology, 2020, 49(11): 252-261.
[24] ELAYYACHY M, IDRISSI A E, HAMMOUTI B. New Thio-Compounds as Corrosion Inhibitor for Steel in 1 M HCl[J]. Corrosion Science, 2006, 48(9): 2470-2479.
[25] 鄧書(shū)端, 李向紅, 杜官本. 2-巰基嘧啶對(duì)冷軋鋼在檸檬酸中的緩蝕性能[J]. 腐蝕科學(xué)與防護(hù)技術(shù), 2017, 29(6): 597-602.
DENG Shu-duan, LI Xiang-hong, DU Guan-ben. Corrosion Inhibition of 2-Mercaptopyrimidine for Cold Rolled Steel in Citric Acid Solution[J]. Corrosion Science and Protection Technology, 2017, 29(6): 597-602.
[26] EL H F, BELKHMIMA R A, ZERGA B, et al. Tempera-ture Performance of a Thione Quinoxaline Compound as Mild Steel Corrosion Inhibitor in Hydrochloric Acid Medium[J]. International Journal of Electrochemical Science, 2014, 9(9): 4721-4731.
[27] 溫福山, 杜永霞, 張涵, 等. 雙咪唑啉緩蝕劑的緩蝕性能評(píng)價(jià)[J]. 腐蝕與防護(hù), 2019, 40(2): 92-100, 109. WEN Fu-shan, DU Yong-xia, ZHANG Han, et al. Eva-lua-tion of Corrosion Inhibition of a Bis-Imidazoline Cor-ro-sion Inhibitor[J]. Corrosion & Protection, 2019, 40(2): 92-100, 109.
[28] DAHIYA S, LATA Su-man, KUMAR R, et al. Compara-tive Performance of Uroniums for Controlling Corrosion of Steel with Methodical Mechanism of Inhibition in Acidic Medium: Part 1[J]. Journal of Molecular Liquids, 2016, 221: 124-132.
[29] AMIN M A, KHALED K F, FADL-ALLAH S A. Testing Validity of the Tafel Extrapolation Method for Moni-toring Corrosion of Cold Rolled Steel in HCl Solutions: Experimental and Theoretical Studies[J]. Corrosion Scien-ce, 2010, 52(1): 140-151.
[30] LI Xiang-hong, DENG Shu-duan, FU Hui, et al. Adsorp-tion and Inhibition Effect of 6-Benzylaminopurine on Cold Rolled Steel in 1.0 M HCl[J]. Electrochimica Acta, 2009, 54(16): 4089-4098.
[31] CHETOUANI A, AOUNITI A, HAMMOUTI B, et al. Corrosion Inhibitors for Iron in Hydrochloride Acid Solution by Newly Synthesised Pyridazine Derivatives[J]. Corrosion Science, 2003, 45(8): 1675-1684.
[32] D?NER A, KARDA? G. N-Aminorhodanine as an Effective Corrosion Inhibitor for Mild Steel in 0.5 M H2SO4[J]. Corrosion Science, 2011, 53(12): 4223-4232.
[33] BOBINA M, KELLENBERGER A, MILLET J P, et al. Corrosion Resistance of Carbon Steel in Weak Acid Solutions in the Presence of L-Histidine as Corrosion Inhibitor[J]. Corrosion Science, 2013, 69: 389-395.
[34] 王秀梅, 楊懷玉, 王福會(huì). 兩種季銨鹽化合物在0.5 mol/L HCl溶液中對(duì)碳鋼緩蝕效果的對(duì)比研究[J]. 腐蝕科學(xué)與防護(hù)技術(shù), 2010, 22(4): 338-342.
WANG Xiu-mei, YANG Huai-yu, WANG Fu-hui. A Comparative Investigation on Inhibition Performance of Two Quaternary Ammonium Salts for Mild Steel in 0.5 mol/L HCl Solution[J]. Corrosion Science and Protection Technology, 2010, 22(4): 338-342.
[35] SINGH A, LIN Yuan-hua, ANSARI K R, et al. Electro-chemical and Surface Studies of some Porphines as Corrosion Inhibitor for J55 Steel in Sweet Corrosion Environment[J]. Applied Surface Science, 2015, 359: 331-339.
[36] LI Xiang-hong, DENG Shu-duan, FU Hui. Sodium Molybdate as a Corrosion Inhibitor for Aluminium in H3PO4Solution[J]. Corrosion Science, 2011, 53(9): 2748- 2753.
[37] AHAMAD I, QURAISHI M A. Mebendazole: New and Efficient Corrosion Inhibitor for Mild Steel in Acid Medium[J]. Corrosion Science, 2010, 52(2): 651-656.
[38] YLDZ R. An Electrochemical and Theoretical Evalua-tion of 4,6-Diamino-2-Pyrimidinethiol as a Corrosion Inhibitor for Mild Steel in HCl Solutions[J]. Corrosion Science, 2015, 90: 544-553.
[39] TEZCAN F, YERLIKAYA G, MAHMOOD A, et al. A Novel Thiophene Schiff Base as an Efficient Corrosion Inhibitor for Mild Steel in 1.0?M HCl: Electrochemical and Quantum Chemical Studies[J]. Journal of Molecular Liquids, 2018, 269: 398-406.
[40] WANG B, DU M, ZHANG J, et al. Electrochemical and Surface Analysis Studies on Corrosion Inhibition of Q235 Steel by Imidazoline Derivative Against CO2Corro-sion[J]. Corrosion Science, 2011, 53(1): 353-361.
[41] 張銀輝, 王瑋, 常洪莉, 等. 鹽酸溶液中Tween-80和CTAB對(duì)Q235鋼的緩蝕協(xié)同作用[J]. 表面技術(shù), 2018, 47(10): 11-21.
ZHANG Yin-hui, WANG Wei, CHANG Hong-li, et al. Synergistic Effect of Tween-80 and CTAB on Corrosion Inhibition of Q235 Steel in HCl Solution[J]. Surface Technology, 2018, 47(10): 11-21.
[42] WANG Xiu-mei, YANG Huai-yu, WANG Fu-hui. An Investigation of Benzimidazole Derivative as Corrosion Inhibitor for Mild Steel in Different Concentration HCl Solutions[J]. Corrosion Science, 2011, 53(1): 113-121.
[43] YU Zong-xue, LIU Yu-chuan, LIANG Ling, et al. Inhibition Performance of a Multi-Sites Adsorption Type Corrosion Inhibitor on P110 Steel in Acidic Medium[J]. Chemical Physics Letters, 2019, 735: 136773.
[44] 呂艷麗, 王艷秋, 周麗, 等. 鄰菲羅啉及其衍生物在1 mol/L鹽酸中的緩蝕性能研究[J]. 表面技術(shù), 2018, 47(10): 51-58.
LYU Yan-li, WANG Yan-qiu, ZHOU Li, et al. Corrosion Inhibition of 1,10-Phenanthroline and Its Derivative on Mild Steel in 1 mol/L HCl[J]. Surface Technology, 2018, 47(10): 51-58.
[45] ZARROUK A, HAMMOUTI B, DAFALI A, et al. Inhibitive Properties and Adsorption of Purpald as a Corrosion Inhibitor for Copper in Nitric Acid Medium[J]. Industrial & Engineering Chemistry Research, 2013, 52(7): 2560-2568.
[46] 王秀梅, 萬(wàn)曄, 楊懷玉. 雙苯并咪唑化合物對(duì)碳鋼在H2SO4溶液中的緩蝕作用[J]. 腐蝕科學(xué)與防護(hù)技術(shù), 2012, 24(4): 296-300.
WANG Xiu-mei, WAN Ye, YANG Huai-yu. Corrosion Inhibition of Mild Steel in H2SO4Solution by Bis- Benzimidazole Compound[J]. Corrosion Science and Prot-ection Technology, 2012, 24(4): 296-300.
[47] ZARROK H, AL D S S, ZARROUK A, et al. Thermody-na-mic Characterisation and Density Functional Theory Investigation of 1,1′,5,5′-Tetramethyl-1H,1′H-3,3′-Bipyra-zole as Corrosion Inhibitor of C38 Steel Corrosion in HCl[J]. International Journal of Electrochemical Science, 2012, 7(5): 4047-4063.
[48] OBOT I B, EBENSO E E, AKPAN I A, et al. Ther-modynamic and Density Functional Theory Investigation of Sulphathiazole as Green Corrosion Inhibitor at Mild Steel/Hydrochloric Acid Interface[J]. International Jour-nal of Electrochemical Science, 2012, 7(3): 1978-1996.
[49] HOSEIN ZADEH A R, DANAEE I, MADDAHY M H. Thermodynamic and Adsorption Behaviour of Medicinal Nitramine as a Corrosion Inhibitor for AISI Steel Alloy in HCl Solution[J]. Journal of Materials Science & Tech-nology, 2013, 29(9): 884-892.
Corrosion Inhibition Property and Mechanism of Diacetophenone Imidazoline Quaternary Salt for Carbon Steel in HCl Solution
1,2,1,2,1,1,2,1,2,1
(1. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China; 2. School of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, China)
The work aimed to synthesize a new diacetophenone imidazoline quaternary ammonium salt compound (labeled PPLB) and evaluate its corrosion inhibition performance for Q235 steel in 0.5 mol/L HCl solution by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscope (SEM). The inhibition mechanism of PPLB was also discussed. The diacetophenone imidazoline quaternary ammonium salt compound was prepared from organic amine, stearic acid, acetophenone and benzyl chloride by dehydration, cyclization, Mannich reaction and quaternization. The weight loss measurement results showed that with the increasing of PPLB concentration and medium temperature, the inhibition efficiency increased gradually, and when the inhibitor dosage was 4.8×10?4mol/L, the inhibition efficiency reached to 98.9% at 353 K, proving that the PPLB was an excellent corrosion inhibitor for Q235 steel in HCl solution. Electrochemical studies indicated that the inhibitor simultaneously retarded both cathodic and anodic processes and acted as a mixed type inhibitor. The PPLB molecules absorbed on metal surface merely by geometric blocking mechanism and the corrosion reaction mechanism was not changed. Besides, the adsorption behavior of PPLB was in accordance with the Langmuir adsorption isotherm. After the addition of PPLB, the charge transfer resistance and film resistance values obviously enhanced, while the double layer capacitance and film capacitance significantly reduced, suggesting that the inhibitor molecules took effects by adsorbing at the metal/solution interface. The thermodynamic parameters deduced from experimental data revealed that the adsorption of inhibitor PPLB was a spontaneously chemical process. The inhibitor molecules may take effects by adsorbing on mild surface via lone pair electrons of nitrogen and oxygen atoms, which could lead to the increase of surface coverage of PPLB molecules on the Q235 steel surface. The inhibition performance was also evidenced by scanning electron microscope. Compared with the sample in 0.5 mol/L HCl solution, the surface of specimen in the presence of PPLB was much smoother. These results confirmed that the PPLB can effectively protect mild steels from corrosion in 0.5 mol/L HCl solution.
inhibitor; quaternary ammonium salt; carbon steel; electrochemistry; adsorption; acidic corrosion
2021-03-20;
2021-05-26
LI Wen-tao (1996—), Female, Postgraduate, Research focus: corrosion inhibitor.
楊懷玉(1963—),男,博士,研究員,主要研究方向?yàn)榫徫g劑。
Corresponding author:YANG Huai-yu (1963—), Male, Doctor, Researcher, Research focus: corrosion inhibitor.
李文濤, 吳浩, 王璇, 等. HCl介質(zhì)中二苯乙酮咪唑啉季銨鹽對(duì)碳鋼的緩蝕行為及機(jī)制[J]. 表面技術(shù), 2022, 51(1): 121-130.
TG172
A
1001-3660(2022)01-0121-10
10.16490/j.cnki.issn.1001-3660.2022.01.013
2021-03-20;
2021-05-26
李文濤(1996—),女,碩士研究生,主要研究方向?yàn)榫徫g劑。
LI Wen-tao, WU Hao, WANG Xuan, et al. Corrosion Inhibition Property and Mechanism of Diacetophenone Imidazoline Quaternary Salt for Carbon Steel in HCl Solution[J]. Surface Technology, 2022, 51(1): 121-130.