熱噴涂鋅鋁合金超疏水涂層的制備及性能 - 圖文-

1、 第29卷第7期2015年7月材料研究學報CHINESE JOURNAL OF MATERIALS RESEARCHV ol.29No.7July2015熱噴涂鋅鋁合金超疏水涂層的制備及性能*孫小東1,2劉剛2李龍陽2劉二勇2陸文聰1曾志翔2烏學東21.上海大學理學院上海2004442.中國科學院寧波材料技術(shù)與工程研究所海洋新材料與應用技術(shù)重點實驗室浙江省海洋材料與防護技術(shù)重點實驗室寧波315201摘要用電弧噴涂技術(shù)在Q235鋼板上噴涂鋅鋁合金涂層,用硬脂酸/乙醇的表面修飾技術(shù)在鋅鋁合金涂層表面構(gòu)筑了一層超疏水膜。用接觸角測量儀(OCA-20,掃描電子顯微鏡(SEM和智能型傅立葉紅外光譜儀(A

2、TR等手段表征了涂層修飾前后的潤濕性、表面形貌以及化學結(jié)構(gòu),并用三電極體系電化學工作站(Solartron analytical對硬脂酸表面修飾前后鋅鋁涂層進行了阻抗譜和極化測試。結(jié)果表明:熱噴涂鋅鋁涂層具有微/納復合結(jié)構(gòu),修飾前涂層表現(xiàn)為親水性,因為金屬涂層具有高表面能;經(jīng)過硬脂酸表面修飾后涂層的靜態(tài)接觸角達到153.2°,滾動角小于10°紅外分析結(jié)果表明,鋅鋁涂層表面由大量的疏水性烴基長鏈組成,有超疏水作用;腐蝕測試結(jié)果表明,修飾處理能明顯提高鋅鋁涂層的防腐蝕性。涂層表面形成的超疏水膜阻礙了界面電化學反應腐蝕產(chǎn)物的脫落與溶解,提高了電荷轉(zhuǎn)移電阻,降低了電流腐蝕密度,從而

3、提高了涂層的防腐蝕性。關(guān)鍵詞材料失效與保護,熱噴涂鋅鋁合金涂層,表面修飾,疏水機理,腐蝕行為分類號TG178文章編號1005-3093(201507-0523-06Preparation and Properties of SuperhydrophobiztedSprayed Zn-Al Coating SUN Xiaodong1,2LIU Gang2LI Longyang2LIU Eryong2LU Wencong1*ZENG Zhixiang2*WU Xuedong21.College of Science,Shanghai University,Shanghai200444,China2

4、.Key Laboratory of Marine Materials and Application and Zhejiang Key Laboratory of Marine Materials andProtective Technologies,Ningbo Institute of Materials Technology and Engineering,Chinese Academy of Science,Ningbo315201,China*Supported by the National Basic Research Program of China No.2014CB643

5、302,National Natural Science Foun-dation of China No.51335010,China Postdoctoral Science Foundation No.2014M551784,the Foundation for Se-lected Postdoctoral Project of Zhejiang Province No.BSH1401040,State Key Laboratory for Mechanical Behaviorof Materials Foundation No.20141605,Zhejiang Provincial

6、Innovation Team No.2011R50006and Ningbo Munici-pal Nature Science Foundation No.2014A610010.Manuscript received November25,2014;in revised form February23,2015.*To whom correspondence should be addressed,Tel:(02166132928-3513,(057486685036,E-mail:wclu,zengzhxABSTRACT A superhydrophobic ZnAl coating

7、was prepared by the electric arc spraying technologyand then surface modification by stearic acid/ethanol.The surface wettability,morphology and chemicalstructure of the ZnAl coating before and after modification were characterized by contact angle measure-ment(OCA-20,scanning electron microscope(SE

8、Mand artificial FTIR spectrometer(ATR,respective-ly.The impedance spectrum and polarization curves of the coatings were measuared by electrochemicalworkstation(Solartron Analyticalwith three electrodes system.The results show that the as sprayed*國家重點基礎研究發(fā)展計劃2014CB643302、國家自然科學基金重點項目51335010、中國博士后科學基

9、金2014M551784、浙江省博士后科研擇優(yōu)資助項目BSH1401040、金屬強度國家重點實驗室開放課題20141605、浙江省重點科技創(chuàng)新團隊項目2011R50006和寧波市自然科學基金2014A610010資助。2014年11月25日收到初稿;2015年2月23日收到修改稿。本文聯(lián)系人:陸文聰,教授;曾志翔,研究員材料研究學報29卷ZnAl coating consists of irregular micro-and nano-sized alloy particles and pores,and exhibits clear hy-drophilicity,which may be

10、ascribed to the high surface energy of metallic coating.After the surface modifi-cation with stearic acid,the static contact angle of the coating reached153.8°with a rolling angle lessthan10°,because there exsited a large number of hydrophobic long alkyl chains on the surface of the modifi

11、ed ZnAl coating.In addition,the surface modification could significantly enhance the corrosion re-sistance of ZnAl coating due to that the thin hydrophobic film plays an important role in supression of thefall off and dissolution of corrosion products on the ZnAl coating,leading to the increase of c

12、harge trans-fer resistance and the corrosion current density.KEY WORDS materials failure and protection,thermal spraying Zn-Al coating,surface modification, hydrophobicity,corrosion behavior自20世紀90年代Barthlott&Neinhuis1揭示了荷葉“自清潔”效應的奧秘以來,基于各種方法在各種基體上制備超疏水表面的研究很多,其關(guān)鍵一點是這種表面由微/納復合結(jié)構(gòu)組成或由低表面能物質(zhì)修飾。例如,B

13、ae等2用電火花線切割加工的方法在鋁合金表面形成了雙尺度正弦圖案,水靜態(tài)接觸角高達156°,而接觸角滯后小于3°。Liu等3用刻蝕鋁箔片的方法在鋁片表面生長出三羥鋁石針狀微納米復合陣列結(jié)構(gòu),隨后用硬脂酸修飾,其水靜態(tài)接觸角達到167°,滾動角為3°。Yu等4則用電化學方法在銅片表面沉積Ni/P涂層,這種涂層具有花蕊般微納米結(jié)構(gòu),水靜態(tài)接觸角也達到了155.5°Lee等5以聚碳酸酯為模板,用熱壓法在高密度聚苯乙烯膜表面形成納米級圓柱狀陣列結(jié)構(gòu),其水靜態(tài)接觸角達到165°。但是上述類似或不同的制備方法6-9都有一個共同的不足:實驗過程復雜

14、、條件苛刻和難以工程化應用。作為一種表面強化技術(shù),熱噴涂不僅噴涂效率高,而且成本低,最重要的是可實現(xiàn)工程化應用。此外,熱噴涂防腐涂層已廣泛應用于現(xiàn)代化工業(yè)、生活中,并且人們對其防腐蝕性能的研究已十分深入10-12,如電子行業(yè)鑄管、停車場、橋梁以及海洋中鋼結(jié)構(gòu)件表面防護。在多種熱噴涂防腐涂層的研究中,電弧噴涂鋅鋁合金以優(yōu)異的長效防護能力和較低的成本得到了廣泛的應用。因此,本文用高速電弧噴涂技術(shù)制備具有一定微納形貌鋅鋁合金涂層,而后用硬脂酸在鋅鋁涂層上構(gòu)筑超疏水表面13,14,研究這種超疏水涂層的疏水機理以及疏水行為對鋅鋁涂層的腐蝕行為的影響。1實驗方法將塊狀Q235低碳鋼(3.5cm×

15、1.5cm樣品分別用丙酮、乙醇、蒸餾水進行超聲清洗,放入烘箱中干燥后進行噴砂處理,使其表面粗糙化。將處理好的樣品固定于噴涂工裝臺上,用高速電弧噴涂設備(上海休瑪XM-400在其表面噴涂一層鋅鋁涂層。將噴涂有鋅鋁涂層的低碳鋼塊浸入到10mmol/L的硬脂酸乙醇溶液中,靜置一定時間后加熱溫度為50。最后將得到的修飾涂層依次用乙醇和蒸餾水清洗,干燥后進行測試。實驗所用試劑均為分析純。用接觸角測量儀(OCA20,Dataphysics,Germa-ny在室溫下測量涂層修飾前后靜態(tài)接觸角,設置測量儀參數(shù)自動轉(zhuǎn)動樣品臺測得滾動角,測量水滴為3L;用智能型傅立葉紅外光譜儀(ATR,Nico-let6700,

16、America表征經(jīng)過硬脂酸修飾的涂層表面;用場發(fā)射掃描電鏡(Quanta FEG250,FEI,America觀察涂層表面形貌;使用電化學工作站(Modulab ECS, Solartron Analytical三電極體系進行電化學測試,將噴涂有鋅鋁涂層的低碳鋼作為工作電極,鉑電極為輔助電極,飽和甘汞電極為參比電極,以3.5%(質(zhì)量分數(shù)NaCl溶液為腐蝕介質(zhì),分別測試涂層修飾前后的耐腐蝕性能。2結(jié)果和討論2.1鋅鋁涂層的表面微織構(gòu)和潤濕性電弧噴涂鋅鋁涂層的形貌及初始接觸角測試結(jié)果,如圖1所示。圖1a中的電弧噴涂鋅鋁涂層表面形貌表明,電弧噴涂涂層表面具有微/納復合結(jié)構(gòu)。進一步放大后(圖1左上插

17、圖可以看出,這些微/納復合結(jié)構(gòu)主要由熔融的微/納尺寸的顆粒狀或棒狀鋅鋁合金堆積而成。用接觸角測量儀測得3L水滴在其表面的接觸角為67.4°(圖1b,表現(xiàn)為親水性。涂層表面的鋅鋁合金及其部分氧化物的高表面能,導致液滴易于鋪展。圖2給出了經(jīng)過硬脂酸乙醇溶液修飾后鋅鋁涂層的接觸角與浸泡時間的關(guān)系圖。由圖2可見,鋅鋁涂層的接觸角隨著在硬脂酸乙醇溶液中浸泡時間延長而逐漸增大,浸泡時間超過48h后接觸角隨時間的延長而減小。例如,當浸泡時間為48h后表面得到最大接觸角為153.2°,72h后接觸角減小為151°,表明制備超疏水鋅鋁涂層適宜的浸泡時間為48h。用SEM分析經(jīng)過硬脂

18、酸乙醇溶液48h修飾后的鋅鋁涂層表面形貌,如圖3a所示。結(jié)果表明,修飾后的鋅鋁涂層表面生長出了微/納米級花狀結(jié)構(gòu),高倍SEM圖表明每個花狀結(jié)構(gòu)是由若干花瓣組 5247期成。接觸角測試的結(jié)果為,接觸角為153.2°(圖3b,滾動角小于10°。這一結(jié)果表明,經(jīng)硬脂酸乙醇溶液改性后的鋅鋁涂層由原始的親水性轉(zhuǎn)變?yōu)槭杷?進一步根據(jù)Cassie-Baxter 方程cos c =f s (cos s +1-1(1分析涂層的接觸行為。式中c 為粗糙表面表觀接觸角,f s 為水滴與固體的接觸面占復合界面的面積分數(shù),s 為本征接觸角。已知鋅鋁涂層磨光滑后接觸角s =86.3°,c

19、=153.2°,代入上式得f s =0.1009。這一結(jié)果表明,水滴在經(jīng)過硬脂酸修飾的鋅鋁涂層表面約90%是與空氣接觸的,只有約10%與表面固體接觸。2.2鋅鋁涂層表面的化學成分硬脂酸修飾前后的鋅鋁涂層表面物相XRD 分析結(jié)果,如圖4所示。由圖4可見,采用硬脂酸修飾前,鋅鋁涂層主要由金屬鋅與金屬鋁相所組成;經(jīng)過圖3硬脂酸修飾后的鋅鋁涂層的表面形貌和表觀接觸角Fig.3Morphology (aand apparent contact angle (bof-modified Zn-Al coating圖4鋅鋁涂層修飾前與修飾后的XRD 衍射圖Fig.4XRD diffraction p

20、attern of ZnAl coating after (aand before modification (b圖2硬脂酸浸泡鋅鋁涂層的時間與接觸角關(guān)系圖Fig.2Relationship between water contact angle and pro-cessing time of ZnAl coating 010203040506070806 810121416 t /h C o n t a c t a n g l e /0306090 2q /(o 圖1熱噴涂鋅鋁涂層的形貌及其表觀接觸角Fig.1Morphology (aand apparent contact angle (

21、bof as-sprayed Zn-Al coating 孫小東等:熱噴涂鋅鋁合金超疏水涂層的制備及性能525材料研究學報29卷表面修飾后鋅鋁涂層的衍射峰出現(xiàn)明顯的變化,在2的5°-30°范圍內(nèi)出現(xiàn)了明顯的幾個衍射峰,如左上放大圖所示。經(jīng)過硬脂酸修飾的鋅鋁涂層表面物相成分發(fā)生了變化,新出現(xiàn)的衍射峰為硬脂酸鋅相15,16。鋅鋁涂層表面的化學成分紅外光譜測試結(jié)果,如圖5所示。硬脂酸的紅外光譜圖表明,在2918cm -1與2849cm -1處的特征吸收峰為-CH 2反對稱與對稱伸縮振動吸收峰,1700cm -1處則為-CO 特征吸收峰。表面修飾后的鋅鋁涂層紅外光譜結(jié)果表明,在36

22、00-3200cm -1處吸收峰為Zn/Al-OH 伸縮振動吸收峰,2918cm -1與2849cm -1處的吸收峰與硬脂酸的特征吸收峰一致,而1538cm -1與1398cm -1處出現(xiàn)了新的吸收峰可推斷為-COO-Al 、-COO-Zn 振動吸收峰17-20。紅外光譜分析結(jié)果表明,鋅鋁涂層經(jīng)硬脂酸乙醇溶液浸泡后成功接枝了疏水性硬脂酸烴基長鏈,形成了低表面能的超疏水涂層。2.3腐蝕電化學行為使用交流阻抗分析軟件ZSimpWin 中相似等效電路(圖6對修飾前后鋅鋁涂層阻抗曲線進行擬合,其示意圖如圖6所示。圖6a 中的Q CPE1為超疏水涂層電容,R c 為超疏水涂層電阻,Q CPE2為涂層雙電

23、層電容;圖6b 中的Q CPE1為涂層電容,C dl 為涂層雙電層電容,R s 都為溶液電阻,R ct 都為電荷轉(zhuǎn)移電阻。根據(jù)以上的研究結(jié)果,超疏水鋅鋁涂層除了表面自組裝生成一層疏水分子層外,其它界面性質(zhì)與鋅鋁涂層相同。此外,擬合結(jié)果表明,修飾前/后鋅鋁涂層阻抗曲線擬合誤差分別為3.80×10-4和2.3×10-3,說明該組等效電路能夠有效反應修飾前后鋅鋁涂層的結(jié)構(gòu)。圖7給出了鋅鋁涂層和超疏水鋅鋁涂層的阻抗曲線的擬合結(jié)果。可以看出,在部分高頻區(qū)鋅鋁涂層的阻抗大于超疏水鋅鋁涂層,而在低頻區(qū)超疏水涂層阻抗則明顯高于鋅鋁涂層。高頻區(qū)對應涂層電容電阻,故可能是硬脂酸分子自組裝形成的

24、超疏水膜不均勻且破壞了部分鈍化層,使腐蝕介質(zhì)更易與鋅鋁接觸反應;低頻區(qū)對應的是電荷轉(zhuǎn)移電阻R ct (電化學反應,在ZSimpWin 擬合參數(shù)中兩者R ct 分別為11.59W ·cm 2和159.2W ·cm 2,可見超疏水涂層主要在界面電化學反應中起作用,通過阻止腐蝕產(chǎn)物的脫落和溶解來提高電荷轉(zhuǎn)移電阻21-23,從而提高了防腐蝕性。將硬脂酸修飾前后的鋅鋁涂層分別在3.5%Na-Cl 溶液中進行動電位極化測試,結(jié)果如圖8所示。圖8表明,硬脂酸修飾前后的鋅鋁涂層的陰極極化曲線沒有明顯的差別,均為氧還原過程,腐蝕電位相差約0.1V 。但是兩種涂層的陽極極化曲線有明顯的不同,其

25、中硬脂酸修飾的鋅鋁涂層在-1.0-1.5V 電位區(qū)間出現(xiàn)明顯的鈍化行為,表明鋅鋁涂層表面生長的硬脂酸分子層能進一步降低腐蝕速圖5硬脂酸與修飾后鋅鋁涂層的紅外譜圖Fig.5IR spectra of stearic acid (aand modified Zn-Al coating (b圖6超疏水鋅鋁涂層和鋅鋁涂層的等效電路圖Fig.6Equivalent circuits of (asuperhydrophobic ZnAlcoating and (bZnAl coating 圖7鋅鋁涂層與超疏水鋅鋁涂層擬合后的Nyquist 圖Fig.7Nyquist image of Zn-Al coat

26、ing and superhydropho-bic Zn-Al coating4000350030002500200015001000500 T /%s /c m -1020406080100120140160180 123456789 Z R e /W c m2Z I m /W c m 25267期率。進一步使用Modulab ECS 軟件對極化曲線作Tafel 曲線分析,結(jié)果表明:硬脂酸修飾與未修飾鋅鋁涂層的腐蝕電流密度分別為1.008×10-5A ·cm 2和2.567×10-5A ·cm 2,可見硬脂酸分子層確實有一定的延緩腐蝕的作用。3結(jié)論使用

27、硬脂酸對具有天然微/納復合結(jié)構(gòu)的鋅鋁涂層進行修飾,可制備出超疏水涂層。在修飾后的表面形成了微/納級花狀結(jié)構(gòu),水滴靜態(tài)接觸角達到153.2°,滾動角小于10°。涂層疏水性能得到改善的原因是,鋅鋁涂層經(jīng)過硬脂酸乙醇溶液浸泡后成功接枝了疏水性硬脂酸烴基長鏈,從而形成了低表面能的超疏水涂層。修飾處理改善了鋅鋁涂層的抗腐蝕性,因為修飾后鋅鋁涂層表面硬脂酸分子層阻礙了腐蝕產(chǎn)物的脫落與溶解,增大了電荷轉(zhuǎn)移電阻,從而抑制了材料的腐蝕。參考文獻1W.Barthlott,C.Neinhuis,Purity of the sacred lotusor escape from contaminat

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