深(shen)海(hai)(hai)環(huan)境(jing)下(xia)(xia)(xia)金(jin)(jin)屬(shu)材料(liao)(liao)的(de)(de)(de)(de)主要(yao)防護(hu)(hu)手(shou)段就(jiu)是(shi)有(you)機涂(tu)(tu)(tu)(tu)(tu)層(ceng)(ceng)(ceng)(ceng)(ceng)(ceng)保護(hu)(hu)[1,2]。有(you)機涂(tu)(tu)(tu)(tu)(tu)層(ceng)(ceng)(ceng)(ceng)(ceng)(ceng)在(zai)服(fu)(fu)(fu)役(yi)(yi)(yi)環(huan)境(jing)下(xia)(xia)(xia)隨服(fu)(fu)(fu)役(yi)(yi)(yi)時(shi)(shi)間延長(chang)而逐步(bu)失(shi)(shi)效(xiao),但這些(xie)失(shi)(shi)效(xiao)行(xing)為難以被(bei)及時(shi)(shi)發(fa)(fa)現(xian)(xian),從(cong)而導(dao)(dao)致(zhi)涂(tu)(tu)(tu)(tu)(tu)層(ceng)(ceng)(ceng)(ceng)(ceng)(ceng)下(xia)(xia)(xia)服(fu)(fu)(fu)役(yi)(yi)(yi)金(jin)(jin)屬(shu)材料(liao)(liao)發(fa)(fa)生(sheng)(sheng)嚴重腐(fu)(fu)蝕問(wen)題,影響深(shen)海(hai)(hai)環(huan)境(jing)下(xia)(xia)(xia)服(fu)(fu)(fu)役(yi)(yi)(yi)金(jin)(jin)屬(shu)構(gou)件的(de)(de)(de)(de)使(shi)(shi)用壽命(ming)及設(she)備的(de)(de)(de)(de)安全性(xing)。為及時(shi)(shi)發(fa)(fa)現(xian)(xian)這些(xie)腐(fu)(fu)蝕問(wen)題,開發(fa)(fa)原位(wei)測試(shi)技術顯得(de)尤(you)為必(bi)要(yao),因此對深(shen)海(hai)(hai)環(huan)境(jing)下(xia)(xia)(xia)服(fu)(fu)(fu)役(yi)(yi)(yi)的(de)(de)(de)(de)有(you)機涂(tu)(tu)(tu)(tu)(tu)層(ceng)(ceng)(ceng)(ceng)(ceng)(ceng)進(jin)行(xing)原位(wei)電化學評價(jia)(jia)是(shi)目前(qian)的(de)(de)(de)(de)熱點課題之一(yi)。本課題組[3-6]前(qian)期(qi)對深(shen)海(hai)(hai)環(huan)境(jing)下(xia)(xia)(xia)有(you)機涂(tu)(tu)(tu)(tu)(tu)層(ceng)(ceng)(ceng)(ceng)(ceng)(ceng)的(de)(de)(de)(de)失(shi)(shi)效(xiao)問(wen)題,尤(you)其(qi)是(shi)失(shi)(shi)效(xiao)機制開展了大(da)(da)量(liang)的(de)(de)(de)(de)研究。結果表明：在(zai)深(shen)海(hai)(hai)壓力(li)作(zuo)用下(xia)(xia)(xia),海(hai)(hai)水(shui)溶液首(shou)先會快(kuai)速(su)滲(shen)入涂(tu)(tu)(tu)(tu)(tu)層(ceng)(ceng)(ceng)(ceng)(ceng)(ceng)內(nei)部,深(shen)海(hai)(hai)的(de)(de)(de)(de)交變(bian)壓力(li)通過“拉(la)拔”作(zuo)用來破壞體系中(zhong)(zhong)的(de)(de)(de)(de)涂(tu)(tu)(tu)(tu)(tu)層(ceng)(ceng)(ceng)(ceng)(ceng)(ceng)/金(jin)(jin)屬(shu)界(jie)面(mian)(mian)(mian)(mian)(mian)的(de)(de)(de)(de)結構(gou),導(dao)(dao)致(zhi)涂(tu)(tu)(tu)(tu)(tu)層(ceng)(ceng)(ceng)(ceng)(ceng)(ceng)從(cong)基體表面(mian)(mian)(mian)(mian)(mian)快(kuai)速(su)剝離;其(qi)次,反復(fu)的(de)(de)(de)(de)壓力(li)交變(bian)循環(huan)致(zhi)使(shi)(shi)涂(tu)(tu)(tu)(tu)(tu)層(ceng)(ceng)(ceng)(ceng)(ceng)(ceng)中(zhong)(zhong)填(tian)料(liao)(liao)/基料(liao)(liao)樹脂界(jie)面(mian)(mian)(mian)(mian)(mian)發(fa)(fa)生(sheng)(sheng)開裂(lie),水(shui)等腐(fu)(fu)蝕介質(zhi)由開裂(lie)處快(kuai)速(su)向(xiang)涂(tu)(tu)(tu)(tu)(tu)層(ceng)(ceng)(ceng)(ceng)(ceng)(ceng)內(nei)部滲(shen)透,破壞涂(tu)(tu)(tu)(tu)(tu)層(ceng)(ceng)(ceng)(ceng)(ceng)(ceng)致(zhi)密性(xing),最終(zhong)導(dao)(dao)致(zhi)大(da)(da)量(liang)水(shui)在(zai)金(jin)(jin)屬(shu)/涂(tu)(tu)(tu)(tu)(tu)層(ceng)(ceng)(ceng)(ceng)(ceng)(ceng)界(jie)面(mian)(mian)(mian)(mian)(mian)水(shui)平(ping)擴展,引(yin)發(fa)(fa)基體金(jin)(jin)屬(shu)腐(fu)(fu)蝕,致(zhi)使(shi)(shi)有(you)機防護(hu)(hu)涂(tu)(tu)(tu)(tu)(tu)層(ceng)(ceng)(ceng)(ceng)(ceng)(ceng)提前(qian)失(shi)(shi)效(xiao)。可見,在(zai)整(zheng)個過程中(zhong)(zhong),金(jin)(jin)屬(shu)/涂(tu)(tu)(tu)(tu)(tu)層(ceng)(ceng)(ceng)(ceng)(ceng)(ceng)界(jie)面(mian)(mian)(mian)(mian)(mian)以及填(tian)料(liao)(liao)/基料(liao)(liao)樹脂界(jie)面(mian)(mian)(mian)(mian)(mian)是(shi)涂(tu)(tu)(tu)(tu)(tu)層(ceng)(ceng)(ceng)(ceng)(ceng)(ceng)體系在(zai)深(shen)海(hai)(hai)環(huan)境(jing)下(xia)(xia)(xia)服(fu)(fu)(fu)役(yi)(yi)(yi)的(de)(de)(de)(de)薄弱(ruo)環(huan)節,它們直接影響著涂(tu)(tu)(tu)(tu)(tu)層(ceng)(ceng)(ceng)(ceng)(ceng)(ceng)的(de)(de)(de)(de)防護(hu)(hu)性(xing)能(neng)。因此,采用電化學方法獲取金(jin)(jin)屬(shu)與有(you)機涂(tu)(tu)(tu)(tu)(tu)層(ceng)(ceng)(ceng)(ceng)(ceng)(ceng)體系的(de)(de)(de)(de)界(jie)面(mian)(mian)(mian)(mian)(mian)狀態隨服(fu)(fu)(fu)役(yi)(yi)(yi)時(shi)(shi)間的(de)(de)(de)(de)演(yan)化規律(lv),可以實現(xian)(xian)對涂(tu)(tu)(tu)(tu)(tu)層(ceng)(ceng)(ceng)(ceng)(ceng)(ceng)服(fu)(fu)(fu)役(yi)(yi)(yi)性(xing)能(neng)的(de)(de)(de)(de)評價(jia)(jia),其(qi)中(zhong)(zhong)電化學阻抗譜 (EIS) 測試(shi)技術就(jiu)是(shi)有(you)效(xiao)的(de)(de)(de)(de)電化學測試(shi)方法之一(yi)[7,8]。

然而,實驗(yan)室內(nei)的(de)(de)傳統電化(hua)(hua)學測試裝置卻無法(fa)直接應(ying)用在現場檢測中。這(zhe)主要(yao)是因(yin)為(wei),一(yi)方(fang)面(mian),傳統的(de)(de)電化(hua)(hua)學測量體系需(xu)設置電解(jie)池(chi),引入外置電極及溶液等,而這(zhe)明顯不符合深海環境(jing)下現場應(ying)用的(de)(de)需(xu)求;另(ling)一(yi)方(fang)面(mian),涂(tu)(tu)料的(de)(de)較大厚(hou)度(du)嚴重(zhong)(zhong)影響了金(jin)屬基(ji)體電化(hua)(hua)學信(xin)號(hao)的(de)(de)準確(que)采(cai)集。一(yi)般(ban)應(ying)用于海洋設施通用部位(wei)(wei)的(de)(de)重(zhong)(zhong)防腐(fu)涂(tu)(tu)料,其防護期效(xiao)(xiao)應(ying)至少達(da)到10 a;對于重(zhong)(zhong)點(dian)部位(wei)(wei)則要(yao)求防護期效(xiao)(xiao)達(da)到15 a以(yi)上(shang),因(yin)此施加的(de)(de)防腐(fu)蝕涂(tu)(tu)層的(de)(de)厚(hou)度(du)則應(ying)達(da)到300 μm以(yi)上(shang)[9]。此時,涂(tu)(tu)層下金(jin)屬基(ji)體反(fan)饋(kui)的(de)(de)電化(hua)(hua)學信(xin)號(hao)將變得非常微弱(ruo),給電化(hua)(hua)學信(xin)息的(de)(de)采(cai)集帶(dai)來很大困難。因(yin)此,如果要(yao)實現深海環境(jing)下有機涂(tu)(tu)層性能的(de)(de)原(yuan)位(wei)(wei)電化(hua)(hua)學準確(que)評價,就需(xu)要(yao)針對性地(di)開展更有效(xiao)(xiao)的(de)(de)原(yuan)位(wei)(wei)測試裝置設計的(de)(de)研究。

近年來,研(yan)(yan)(yan)究(jiu)(jiu)(jiu)(jiu)人員應(ying)(ying)用(yong)微(wei)(wei)電(dian)(dian)(dian)極(ji)技術開展了(le)許多(duo)原位(wei)電(dian)(dian)(dian)化(hua)學(xue)(xue)(xue)測(ce)(ce)(ce)量(liang)或局(ju)(ju)部電(dian)(dian)(dian)化(hua)學(xue)(xue)(xue)反(fan)應(ying)(ying)的(de)研(yan)(yan)(yan)究(jiu)(jiu)(jiu)(jiu)。Simpson等[10]采用(yong)電(dian)(dian)(dian)子束(shu)沉(chen)積法(fa)將(jiang)貴金屬(shu)沉(chen)積在(zai)涂層(ceng)表面形成(cheng)薄片狀微(wei)(wei)電(dian)(dian)(dian)極(ji)。這種微(wei)(wei)電(dian)(dian)(dian)極(ji)制備(bei)(bei)方法(fa)相對復(fu)雜(za),且(qie)微(wei)(wei)電(dian)(dian)(dian)極(ji)本身(shen)容易受到外界(jie)環(huan)(huan)境(jing)(jing)的(de)破(po)壞,在(zai)測(ce)(ce)(ce)量(liang)較厚涂層(ceng)下(xia)的(de)金屬(shu)腐蝕時(shi)靈敏度較低。Courioni等[11]采用(yong)微(wei)(wei)陣列電(dian)(dian)(dian)極(ji)研(yan)(yan)(yan)究(jiu)(jiu)(jiu)(jiu)了(le)不同(tong)(tong)材(cai)料間的(de)電(dian)(dian)(dian)偶電(dian)(dian)(dian)流對電(dian)(dian)(dian)化(hua)學(xue)(xue)(xue)噪聲信(xin)號的(de)影響,雖然裝置(zhi)(zhi)穩(wen)定(ding),但仍未解決需(xu)要外置(zhi)(zhi)裝備(bei)(bei)輔助測(ce)(ce)(ce)量(liang)的(de)問題。還有(you)一些(xie)學(xue)(xue)(xue)者采用(yong)局(ju)(ju)部pH值或電(dian)(dian)(dian)流探針的(de)測(ce)(ce)(ce)試微(wei)(wei)電(dian)(dian)(dian)極(ji)[12,13]來測(ce)(ce)(ce)量(liang)涂層(ceng)體(ti)系的(de)電(dian)(dian)(dian)化(hua)學(xue)(xue)(xue)參數,但這些(xie)研(yan)(yan)(yan)究(jiu)(jiu)(jiu)(jiu)并沒有(you)針對涂層(ceng)體(ti)系的(de)防(fang)護性能(neng)做(zuo)出(chu)有(you)效評(ping)價。總之(zhi),涂層(ceng)研(yan)(yan)(yan)究(jiu)(jiu)(jiu)(jiu)現有(you)的(de)微(wei)(wei)電(dian)(dian)(dian)極(ji)方法(fa)無(wu)法(fa)適用(yong)于深(shen)海環(huan)(huan)境(jing)(jing)的(de)原位(wei)測(ce)(ce)(ce)量(liang),同(tong)(tong)時(shi)針對深(shen)海環(huan)(huan)境(jing)(jing)下(xia)涂層(ceng)原位(wei)電(dian)(dian)(dian)化(hua)學(xue)(xue)(xue)測(ce)(ce)(ce)量(liang)裝置(zhi)(zhi)的(de)研(yan)(yan)(yan)究(jiu)(jiu)(jiu)(jiu)也鮮有(you)報(bao)道。

為了(le)(le)(le)解(jie)決深海環境(jing)下涂(tu)層(ceng)原位(wei)電(dian)(dian)化(hua)學(xue)測(ce)(ce)量(liang)(liang)的(de)(de)問題(ti),本文首先設(she)計(ji)(ji)了(le)(le)(le)一(yi)種(zhong)圓環狀預埋(mai)微(wei)(wei)電(dian)(dian)極。微(wei)(wei)電(dian)(dian)極預先植入有機(ji)涂(tu)層(ceng)內部(bu),避免了(le)(le)(le)采用外置電(dian)(dian)極及厚涂(tu)層(ceng)信號檢測(ce)(ce)困難的(de)(de)問題(ti)。圓環狀的(de)(de)傳(chuan)(chuan)感器設(she)計(ji)(ji)方案使系統電(dian)(dian)位(wei)分布(bu)均勻,保證了(le)(le)(le)電(dian)(dian)化(hua)學(xue)測(ce)(ce)試結(jie)果的(de)(de)準確(que)性。微(wei)(wei)電(dian)(dian)極的(de)(de)幾何(he)尺寸(cun)微(wei)(wei)小,不會對(dui)涂(tu)層(ceng)的(de)(de)防護性能產生明(ming)顯影響。其次,基(ji)于研制的(de)(de)預埋(mai)微(wei)(wei)電(dian)(dian)極,設(she)計(ji)(ji)了(le)(le)(le)相應的(de)(de)EIS原位(wei)測(ce)(ce)試裝置。最后,通過(guo)交變(bian)壓力(li)加速實驗(yan)及與傳(chuan)(chuan)統測(ce)(ce)量(liang)(liang)方式結(jie)果對(dui)比等方法檢驗(yan)了(le)(le)(le)微(wei)(wei)電(dian)(dian)極原位(wei)測(ce)(ce)試的(de)(de)準確(que)性和可靠性。

1 實驗(yan)方法(fa)

1.1 樣品(pin)制備及電化(hua)學測試(shi)

采用環氧(yang)清漆(qi)涂(tu)層體(ti)(ti)(ti)系作為(wei)(wei)研究對象,環氧(yang)樹(shu)脂、固化(hua)劑(ji)及有機溶(rong)劑(ji)的質(zhi)量比為(wei)(wei)1∶0.8∶0.4。制備過(guo)程為(wei)(wei)：將溶(rong)劑(ji)二甲苯加入環氧(yang)樹(shu)脂E-44并磁力攪拌(ban)(ban)0.5 h,待(dai)E-44充分(fen)溶(rong)解后加入固化(hua)劑(ji)TY-650繼續攪拌(ban)(ban)0.5 h,最后在常溫環境(jing)中靜置0.5 h令其(qi)充分(fen)熟化(hua),以待(dai)涂(tu)刷。金屬基(ji)體(ti)(ti)(ti)材(cai)料為(wei)(wei)10Ni5CrMoV低合金高強度(du)(du)鋼,其(qi)主要化(hua)學成(cheng)分(fen) (質(zhi)量分(fen)數,%) 為(wei)(wei)：Ni 4.67,Cr 0.60,Mo 0.46,V 0.065,Mn 0.54,C 0.076,Fe余量。基(ji)體(ti)(ti)(ti)尺寸為(wei)(wei)40 mm×40 mm×2 mm。涂(tu)層/金屬電極工作面積為(wei)(wei)16 cm2,涂(tu)層平均厚度(du)(du)為(wei)(wei)(200±10) μm。

通過Autolab PGSTAT302型電(dian)(dian)化學工作(zuo)站進(jin)(jin)行(xing)EIS測(ce)(ce)量(liang)。采用傳(chuan)統的(de)(de)(de)三電(dian)(dian)極(ji)體系,以涂層(ceng)/金屬電(dian)(dian)極(ji)試樣作(zuo)為(wei)工作(zuo)電(dian)(dian)極(ji),Pt電(dian)(dian)極(ji)作(zuo)為(wei)輔助電(dian)(dian)極(ji) (CE),固(gu)態Ag/AgCl電(dian)(dian)極(ji)為(wei)參比(bi)電(dian)(dian)極(ji) (RE)。EIS測(ce)(ce)試在(zai)開(kai)(kai)路(lu)電(dian)(dian)位(wei)下進(jin)(jin)行(xing),待開(kai)(kai)路(lu)電(dian)(dian)位(wei)穩(wen)定后開(kai)(kai)始測(ce)(ce)量(liang)。測(ce)(ce)試頻率范圍(wei)為(wei)105~10-2 Hz。浸泡初期(qi)施加50 mV (rms) 振(zhen)幅的(de)(de)(de)正(zheng)弦擾動以保證一(yi)定的(de)(de)(de)信(xin)噪(zao)比(bi),后期(qi)振(zhen)幅調整為(wei)20 mV (rms)。文中涉及的(de)(de)(de)交變壓(ya)力(li)(li)實(shi)(shi)驗均在(zai)實(shi)(shi)驗室自制的(de)(de)(de)深(shen)海環境模擬(ni)裝(zhuang)置(zhi)中進(jin)(jin)行(xing)[4]。選取3組不同(tong)幅度的(de)(de)(de)交變壓(ya)力(li)(li)條件進(jin)(jin)行(xing)實(shi)(shi)驗室加速實(shi)(shi)驗,分別(bie)為(wei)：0.1~6.0 MPa,0.1~8.0 MPa以及 0.1~10.0 MPa。每一(yi)個(ge)(ge)交變周期(qi)包括(kuo)12 h的(de)(de)(de)常(chang)壓(ya)階段和12 h的(de)(de)(de)高(gao)靜水壓(ya)階段,每組實(shi)(shi)驗至(zhi)少持續10個(ge)(ge)周期(qi)共240 h。

1.2 預埋微電極(ji)

為了避免在(zai)原位測(ce)量中(zhong)使用外(wai)置電(dian)極(ji),采用了分層(ceng)(ceng)(ceng)刷涂(tu)(tu)涂(tu)(tu)層(ceng)(ceng)(ceng)的(de)(de)方法(fa)將(jiang)微電(dian)極(ji)預先植(zhi)入(ru)涂(tu)(tu)層(ceng)(ceng)(ceng)內(nei)部(bu),使整(zheng)個(ge)環氧清(qing)漆分為內(nei)、外(wai)兩層(ceng)(ceng)(ceng),微電(dian)極(ji)則水平置于(yu)涂(tu)(tu)層(ceng)(ceng)(ceng)內(nei)層(ceng)(ceng)(ceng)和外(wai)層(ceng)(ceng)(ceng)之(zhi)間,其(qi)示意圖(tu)如圖(tu)1所示。首(shou)先,將(jiang)直徑(jing)為50 μm的(de)(de)鉑絲制(zhi)(zhi)成圓環狀的(de)(de)微電(dian)極(ji),以保證電(dian)勢的(de)(de)均勻分布(bu)。然后涂(tu)(tu)覆一(yi)層(ceng)(ceng)(ceng)環氧清(qing)漆于(yu)基體金屬(shu)表(biao)(biao)面,待其(qi)接(jie)(jie)近完全(quan)固(gu)(gu)化(hua)后將(jiang)微電(dian)極(ji)固(gu)(gu)定于(yu)涂(tu)(tu)層(ceng)(ceng)(ceng)表(biao)(biao)面。為了使微電(dian)極(ji)與(yu)涂(tu)(tu)層(ceng)(ceng)(ceng)表(biao)(biao)面完全(quan)貼合(he)并黏附牢固(gu)(gu),配制(zhi)(zhi)少量的(de)(de)環氧清(qing)漆并涂(tu)(tu)覆于(yu)二(er)者之(zhi)間。接(jie)(jie)著在(zai)整(zheng)個(ge)試(shi)樣(yang)(yang)表(biao)(biao)面刷涂(tu)(tu)外(wai)層(ceng)(ceng)(ceng)清(qing)漆并完全(quan)覆蓋微電(dian)極(ji),兩層(ceng)(ceng)(ceng)清(qing)漆的(de)(de)干膜厚(hou)度均為 (100±10) μm。為了與(yu)外(wai)部(bu)的(de)(de)電(dian)化(hua)學測(ce)量儀(yi)器連(lian)接(jie)(jie),微電(dian)極(ji)還(huan)需連(lian)接(jie)(jie)一(yi)段鉑絲制(zhi)(zhi)成的(de)(de)電(dian)極(ji)引線(xian),引線(xian)接(jie)(jie)頭的(de)(de)一(yi)端位于(yu)涂(tu)(tu)層(ceng)(ceng)(ceng)內(nei)部(bu),另一(yi)端延(yan)伸至(zhi)涂(tu)(tu)層(ceng)(ceng)(ceng)外(wai)并與(yu)Cu導線(xian)相連(lian)接(jie)(jie),其(qi)連(lian)接(jie)(jie)處(chu)采用環氧樹(shu)脂封裝,保護接(jie)(jie)口并與(yu)外(wai)界環境絕緣。最后將(jiang)整(zheng)個(ge)試(shi)樣(yang)(yang)在(zai)40 ℃條件下固(gu)(gu)化(hua)4 h,60 ℃固(gu)(gu)化(hua)20 h,再在(zai)室溫條件下 (25 ℃,RH 30%) 放(fang)置7 d,以確保涂(tu)(tu)料的(de)(de)固(gu)(gu)化(hua)完全(quan)及溶劑的(de)(de)完全(quan)揮(hui)發(fa)。

圖(tu)1 裝有預埋微電極的涂層/金(jin)屬電極試樣示意(yi)圖(tu)

2 結果(guo)與討論

2.1 針對電化學阻抗譜測試的原(yuan)位測試裝置設計

為(wei)(wei)(wei)了驗(yan)證(zheng)上述預(yu)埋(mai)微(wei)電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)的(de)(de)有效性,將制成的(de)(de)微(wei)電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)試樣直接用(yong)于EIS的(de)(de)測試。根據阻抗測量原理,將直徑為(wei)(wei)(wei)2 cm的(de)(de)圓環狀鉑微(wei)電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)作(zuo)為(wei)(wei)(wei)參(can)比電(dian)(dian)(dian)極(ji)(ji)(ji)(ji),基體(ti)金(jin)屬作(zuo)為(wei)(wei)(wei)工作(zuo)電(dian)(dian)(dian)極(ji)(ji)(ji)(ji),另(ling)加(jia)一個外置的(de)(de)Pt電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)作(zuo)為(wei)(wei)(wei)輔助電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)。同(tong)時制備一組普通的(de)(de)傳統(tong)三電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)裝(zhuang)置在(zai)相同(tong)條件下進行阻抗測試。表1為(wei)(wei)(wei)常規的(de)(de)及預(yu)埋(mai)微(wei)電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)的(de)(de)涂層(ceng)/金(jin)屬電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)試樣在(zai)浸泡不同(tong)時間后所測得的(de)(de)低頻阻抗模值(zhi)|Z |0.01 Hz。可以看出,裝(zhuang)有預(yu)埋(mai)微(wei)電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)的(de)(de)清漆涂層(ceng)試樣與傳統(tong)裝(zhuang)置的(de)(de)試樣測試結果非常接近,說明此涂層(ceng)體(ti)系中采用(yong)電(dian)(dian)(dian)位較(jiao)為(wei)(wei)(wei)穩定(ding)的(de)(de)Pt微(wei)電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)作(zuo)為(wei)(wei)(wei)微(wei)參(can)比電(dian)(dian)(dian)極(ji)(ji)(ji)(ji)是可行的(de)(de)。

然而,這種(zhong)預埋(mai)微(wei)(wei)(wei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)試樣并沒有(you)完全避免外置電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)的(de)使用,尚不(bu)(bu)能(neng)(neng)在(zai)(zai)現場進行(xing)原位(wei)的(de)EIS測量。為(wei)此(ci),本(ben)文首(shou)先考慮采(cai)用兩(liang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)體系(xi)(xi)進行(xing)EIS測試,即金屬(shu)基(ji)體作為(wei)工(gong)作電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji),預埋(mai)的(de)Pt微(wei)(wei)(wei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)同時(shi)(shi)(shi)作為(wei)輔(fu)助和參比電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)。事實上,當(dang)工(gong)作電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)的(de)面積(ji)(ji)較(jiao)小時(shi)(shi)(shi),極(ji)(ji)(ji)化回路中的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流不(bu)(bu)能(neng)(neng)引起(qi)輔(fu)助電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)的(de)極(ji)(ji)(ji)化,因此(ci)輔(fu)助電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)在(zai)(zai)測量中可(ke)保持穩定(ding),此(ci)時(shi)(shi)(shi)可(ke)將輔(fu)助電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)作為(wei)測量電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路中的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)基(ji)準,即參比電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)沉積(ji)(ji)、電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)致變色等研(yan)究常(chang)常(chang)采(cai)用兩(liang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)體系(xi)(xi),許多特殊環境下的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)化學阻抗測量也是采(cai)用兩(liang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)體系(xi)(xi)完成(cheng)的(de)[14,15]。但是,本(ben)實驗采(cai)用兩(liang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)方(fang)法并沒有(you)獲得正常(chang)、有(you)效的(de)阻抗數據。主要的(de)原因可(ke)能(neng)(neng)是微(wei)(wei)(wei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)的(de)面積(ji)(ji)微(wei)(wei)(wei)小,作為(wei)輔(fu)助電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)時(shi)(shi)(shi)其自(zi)身電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)在(zai)(zai)回路中并不(bu)(bu)能(neng)(neng)保持穩定(ding),微(wei)(wei)(wei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)同時(shi)(shi)(shi)做參比、輔(fu)助電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)的(de)方(fang)法不(bu)(bu)可(ke)行(xing)。

為了(le)將微電極(ji)(ji)技術應用于EIS的測試,本實(shi)驗對裝置(zhi)模型(xing)進行了(le)改進,設計了(le)適用于EIS的雙微電極(ji)(ji)裝置(zhi),如圖2所示。兩個(ge)圓環狀Pt微電極(ji)(ji)分別作為RE與CE預先植入有機涂層內部(bu)并處于同(tong)一平面,使其不(bu)易受到(dao)交(jiao)變壓力環境的影(ying)響。微電極(ji)(ji)之間(jian)相對距離比較接近(jin)但各自的引線(xian)部(bu)分避免了(le)直接接觸,測量時金屬(shu)基(ji)體作為工作電極(ji)(ji)。

圖(tu)2 適用(yong)于電化(hua)學阻抗測試(shi)的雙微電極裝(zhuang)置示意圖(tu)

為(wei)驗(yan)證雙微(wei)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)裝(zhuang)置測(ce)(ce)試的(de)(de)(de)(de)(de)(de)準確性,待其(qi)阻(zu)抗(kang)(kang)(kang)測(ce)(ce)量完畢后(hou)即置換(huan)外置參(can)比(bi)(bi)和輔助電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)再(zai)一次進(jin)行測(ce)(ce)量。這種(zhong)(zhong)傳(chuan)統測(ce)(ce)量裝(zhuang)置與雙微(wei)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)裝(zhuang)置的(de)(de)(de)(de)(de)(de)EIS結(jie)果如(ru)圖(tu)(tu)3所示(shi)。圖(tu)(tu)3a為(wei)浸泡(pao)2 h的(de)(de)(de)(de)(de)(de)Nyquist圖(tu)(tu),其(qi)中(zhong)(zhong)傳(chuan)統電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)試樣(yang)(yang)所測(ce)(ce)得(de)的(de)(de)(de)(de)(de)(de)曲線呈單容抗(kang)(kang)(kang)弧(hu)特(te)征(zheng),而微(wei)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)試樣(yang)(yang)的(de)(de)(de)(de)(de)(de)結(jie)果為(wei)近(jin)乎(hu)直線且無(wu)法(fa)采用(yong)有效的(de)(de)(de)(de)(de)(de)等效電(dian)(dian)(dian)(dian)(dian)路(lu)進(jin)行擬合,二者有著明(ming)(ming)顯(xian)(xian)的(de)(de)(de)(de)(de)(de)差別;浸泡(pao)26 h后(hou) (圖(tu)(tu)3b),二者的(de)(de)(de)(de)(de)(de)譜(pu)圖(tu)(tu)形狀(zhuang)逐(zhu)漸(jian)接近(jin),此(ci)時采用(yong)具(ju)有兩個(ge)時間常數的(de)(de)(de)(de)(de)(de)等效電(dian)(dian)(dian)(dian)(dian)路(lu)可(ke)以(yi)得(de)到較好的(de)(de)(de)(de)(de)(de)擬合結(jie)果;浸泡(pao)到第136 h (圖(tu)(tu)3c),兩種(zhong)(zhong)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)試樣(yang)(yang)的(de)(de)(de)(de)(de)(de)測(ce)(ce)試結(jie)果均又(you)呈現(xian)為(wei)單容抗(kang)(kang)(kang)的(de)(de)(de)(de)(de)(de)特(te)征(zheng),微(wei)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)試樣(yang)(yang)的(de)(de)(de)(de)(de)(de)容抗(kang)(kang)(kang)弧(hu)半徑(jing)較小,考慮到坐標比(bi)(bi)例的(de)(de)(de)(de)(de)(de)關系,二者結(jie)果的(de)(de)(de)(de)(de)(de)差別并(bing)不明(ming)(ming)顯(xian)(xian)。兩種(zhong)(zhong)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)試樣(yang)(yang)測(ce)(ce)試的(de)(de)(de)(de)(de)(de)低頻阻(zu)抗(kang)(kang)(kang)模值|Z |0.01 Hz擬合結(jie)果見表(biao)2。其(qi)中(zhong)(zhong)微(wei)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)試樣(yang)(yang)浸泡(pao)2 h的(de)(de)(de)(de)(de)(de)數據因沒(mei)有擬合而無(wu)法(fa)獲得(de)具(ju)體(ti)數值。通(tong)過分析可(ke)知,作為(wei)參(can)比(bi)(bi)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)的(de)(de)(de)(de)(de)(de)微(wei)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)埋在涂層內(nei)部,當沒(mei)有水滲(shen)透到達(da)其(qi)表(biao)面時處于絕(jue)緣(yuan)狀(zhuang)態,此(ci)時測(ce)(ce)得(de)的(de)(de)(de)(de)(de)(de)阻(zu)抗(kang)(kang)(kang)數據與真實結(jie)果偏差較大。以(yi)此(ci)特(te)征(zheng)可(ke)用(yong)來判斷水向涂層內(nei)滲(shen)透的(de)(de)(de)(de)(de)(de)程度。隨浸泡(pao)時間延長(chang),水進(jin)入涂層內(nei)部,此(ci)時微(wei)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)試樣(yang)(yang)的(de)(de)(de)(de)(de)(de)測(ce)(ce)量阻(zu)抗(kang)(kang)(kang)模值出現(xian)明(ming)(ming)顯(xian)(xian)信息,并(bing)且結(jie)果與傳(chuan)統試樣(yang)(yang)的(de)(de)(de)(de)(de)(de)測(ce)(ce)試結(jie)果相吻合,說明(ming)(ming)采用(yong)雙微(wei)電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)試樣(yang)(yang)可(ke)以(yi)獲得(de)準確的(de)(de)(de)(de)(de)(de)EIS結(jie)果。

圖3 通過傳統測量方式與雙微(wei)電極試(shi)樣測試(shi)的浸泡不(bu)同時間(jian)涂層的EIS

2.2 交變壓力環境(jing)下阻抗(kang)微電(dian)極裝置的可靠性(xing)

前(qian)(qian)期研究[3-5]結(jie)(jie)(jie)果表明(ming)(ming),深海(hai)交(jiao)(jiao)(jiao)(jiao)(jiao)變(bian)(bian)壓(ya)(ya)(ya)力(li)(li)能(neng)(neng)夠(gou)使有(you)機涂(tu)(tu)(tu)層(ceng)(ceng)快速(su)(su)失效(xiao)(xiao)。隨著交(jiao)(jiao)(jiao)(jiao)(jiao)變(bian)(bian)壓(ya)(ya)(ya)力(li)(li)幅度的(de)(de)(de)(de)(de)增大(da),涂(tu)(tu)(tu)層(ceng)(ceng)失效(xiao)(xiao)的(de)(de)(de)(de)(de)速(su)(su)度加快,且不(bu)同(tong)交(jiao)(jiao)(jiao)(jiao)(jiao)變(bian)(bian)壓(ya)(ya)(ya)力(li)(li)下(xia)(xia)(xia)(xia)涂(tu)(tu)(tu)層(ceng)(ceng)的(de)(de)(de)(de)(de)失效(xiao)(xiao)形式不(bu)發生改變(bian)(bian)。因(yin)此,交(jiao)(jiao)(jiao)(jiao)(jiao)變(bian)(bian)壓(ya)(ya)(ya)力(li)(li)是(shi)深海(hai)環(huan)境(jing)(jing)下(xia)(xia)(xia)(xia)對(dui)有(you)機涂(tu)(tu)(tu)層(ceng)(ceng)防護(hu)性(xing)能(neng)(neng)影響最(zui)為顯著的(de)(de)(de)(de)(de)環(huan)境(jing)(jing)因(yin)素。針(zhen)對(dui)這一(yi)(yi)深海(hai)環(huan)境(jing)(jing)的(de)(de)(de)(de)(de)特點,以(yi)交(jiao)(jiao)(jiao)(jiao)(jiao)變(bian)(bian)壓(ya)(ya)(ya)力(li)(li)為主要變(bian)(bian)量的(de)(de)(de)(de)(de)實驗(yan)(yan)室加速(su)(su)實驗(yan)(yan)可(ke)對(dui)有(you)機涂(tu)(tu)(tu)層(ceng)(ceng)服役性(xing)能(neng)(neng)進(jin)行快速(su)(su)、有(you)效(xiao)(xiao)的(de)(de)(de)(de)(de)評價。因(yin)此,為了驗(yan)(yan)證上述研制的(de)(de)(de)(de)(de)涂(tu)(tu)(tu)層(ceng)(ceng)微電極裝(zhuang)置(zhi)應(ying)用于阻(zu)(zu)抗(kang)測試(shi)的(de)(de)(de)(de)(de)可(ke)靠性(xing),在(zai)一(yi)(yi)系列不(bu)同(tong)強(qiang)度的(de)(de)(de)(de)(de)交(jiao)(jiao)(jiao)(jiao)(jiao)變(bian)(bian)壓(ya)(ya)(ya)力(li)(li)加速(su)(su)實驗(yan)(yan)下(xia)(xia)(xia)(xia)進(jin)行了涂(tu)(tu)(tu)層(ceng)(ceng)的(de)(de)(de)(de)(de)EIS測試(shi)。圖4為各(ge)壓(ya)(ya)(ya)力(li)(li)加速(su)(su)實驗(yan)(yan)下(xia)(xia)(xia)(xia)微電極裝(zhuang)置(zhi)測得的(de)(de)(de)(de)(de)涂(tu)(tu)(tu)層(ceng)(ceng)阻(zu)(zu)抗(kang)模值(zhi)結(jie)(jie)(jie)果。可(ke)以(yi)看(kan)出(chu),0.1~3.5 MPa交(jiao)(jiao)(jiao)(jiao)(jiao)變(bian)(bian)壓(ya)(ya)(ya)力(li)(li)下(xia)(xia)(xia)(xia),涂(tu)(tu)(tu)層(ceng)(ceng)的(de)(de)(de)(de)(de)阻(zu)(zu)抗(kang)模值(zhi)隨浸泡時(shi)(shi)間(jian)(jian)延(yan)長而逐漸(jian)下(xia)(xia)(xia)(xia)降(jiang),浸泡240 h后(hou)|Z |從(cong)1010 Ωcm2以(yi)下(xia)(xia)(xia)(xia)降(jiang)到(dao)約3×108 Ωcm2。0.1~6.0 MPa條件下(xia)(xia)(xia)(xia),|Z |值(zhi)在(zai)相(xiang)(xiang)(xiang)同(tong)浸泡時(shi)(shi)間(jian)(jian)內(nei)下(xia)(xia)(xia)(xia)降(jiang)到(dao)1×108 Ωcm2。0.1~8.1和0.1~10.0 MPa下(xia)(xia)(xia)(xia),|Z |值(zhi)分別下(xia)(xia)(xia)(xia)降(jiang)到(dao)107和106數量級。結(jie)(jie)(jie)果表明(ming)(ming),相(xiang)(xiang)(xiang)同(tong)時(shi)(shi)間(jian)(jian)內(nei)交(jiao)(jiao)(jiao)(jiao)(jiao)變(bian)(bian)壓(ya)(ya)(ya)力(li)(li)幅值(zhi)越(yue)大(da),涂(tu)(tu)(tu)層(ceng)(ceng)防護(hu)性(xing)能(neng)(neng)下(xia)(xia)(xia)(xia)降(jiang)越(yue)明(ming)(ming)顯。從(cong)圖5中(zhong)可(ke)以(yi)看(kan)出(chu),交(jiao)(jiao)(jiao)(jiao)(jiao)變(bian)(bian)壓(ya)(ya)(ya)力(li)(li)幅值(zhi)越(yue)大(da),基體金(jin)屬腐蝕越(yue)明(ming)(ming)顯。因(yin)此,測試(shi)的(de)(de)(de)(de)(de)阻(zu)(zu)抗(kang)模值(zhi)變(bian)(bian)化(hua)趨勢與(yu)加速(su)(su)實驗(yan)(yan)后(hou)金(jin)屬基體的(de)(de)(de)(de)(de)宏(hong)觀表面(mian)形貌變(bian)(bian)化(hua)趨勢相(xiang)(xiang)(xiang)一(yi)(yi)致。加速(su)(su)實驗(yan)(yan)下(xia)(xia)(xia)(xia)的(de)(de)(de)(de)(de)EIS測試(shi)結(jie)(jie)(jie)果穩(wen)定,與(yu)前(qian)(qian)期的(de)(de)(de)(de)(de)研究結(jie)(jie)(jie)果吻合,在(zai)量值(zhi)上與(yu)前(qian)(qian)期測試(shi)結(jie)(jie)(jie)果也(ye)相(xiang)(xiang)(xiang)同(tong)[4-6],這表明(ming)(ming)新研制的(de)(de)(de)(de)(de)阻(zu)(zu)抗(kang)微電極測試(shi)裝(zhuang)置(zhi)不(bu)僅在(zai)普通水溶液中(zhong),而且在(zai)深海(hai)環(huan)境(jing)(jing)下(xia)(xia)(xia)(xia),尤其(qi)是(shi)壓(ya)(ya)(ya)力(li)(li)交(jiao)(jiao)(jiao)(jiao)(jiao)變(bian)(bian)環(huan)境(jing)(jing)下(xia)(xia)(xia)(xia),可(ke)以(yi)準確、可(ke)靠的(de)(de)(de)(de)(de)進(jin)行原位電化(hua)學阻(zu)(zu)抗(kang)測試(shi),其(qi)具有(you)良(liang)好的(de)(de)(de)(de)(de)可(ke)靠性(xing)。

圖5 不(bu)同幅(fu)值交變壓(ya)力加速實驗240 h后金屬基體的宏觀表面形貌

3 結論

(1) 設計了一(yi)種預先植入(ru)涂層內部(bu)的(de)圓(yuan)環狀Pt微電(dian)極,解決了原位測試電(dian)極在使用過程中外置電(dian)極不(bu)易安裝(zhuang)以及有機(ji)涂層本身(shen)厚度對電(dian)化學測試信號的(de)影響(xiang)等缺點。

(2) 根據電(dian)(dian)(dian)化學(xue)阻抗譜的(de)測量原理(li)設計(ji)了雙(shuang)微電(dian)(dian)(dian)極(ji)裝(zhuang)(zhuang)置,采用兩(liang)個Pt微電(dian)(dian)(dian)極(ji)分別作為參(can)比電(dian)(dian)(dian)極(ji)和輔助電(dian)(dian)(dian)極(ji)。其阻抗測量結果與(yu)傳統測量裝(zhuang)(zhuang)置結果有較好的(de)一致性(xing),證明了微電(dian)(dian)(dian)極(ji)裝(zhuang)(zhuang)置測試的(de)準(zhun)確(que)性(xing)。

(3) 深海(hai)交變壓(ya)(ya)力(li)加(jia)速實驗(yan)下(xia)(xia),預埋(mai)微電極裝置測得的涂層(ceng)阻(zu)抗模值(zhi)隨浸泡時間延長(chang)而(er)逐漸下(xia)(xia)降(jiang);相同時間內交變壓(ya)(ya)力(li)幅(fu)值(zhi)越(yue)大(da),涂層(ceng)防護性(xing)能下(xia)(xia)降(jiang)越(yue)明顯。測試結果(guo)與傳統裝置測試結果(guo)一(yi)致,證(zheng)明了預埋(mai)微電極在深海(hai)環(huan)境下(xia)(xia)應用的可靠性(xing)。