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電偶腐蝕影響因素研究進展

2022-04-12 02:14:32 changyuan

電(dian)(dian)偶(ou)(ou)腐(fu)(fu)(fu)蝕(shi)(shi)(亦稱接(jie)觸腐(fu)(fu)(fu)蝕(shi)(shi)),是指當(dang)兩種(zhong)或兩種(zhong)以上(shang)不同(tong)金(jin)(jin)屬(shu)在導電(dian)(dian)介質中(zhong)接(jie)觸后,由于各自電(dian)(dian)極(ji)電(dian)(dian)位不同(tong)而(er)構成腐(fu)(fu)(fu)蝕(shi)(shi)原電(dian)(dian)池。電(dian)(dian)位較正的金(jin)(jin)屬(shu)為陰極(ji),發(fa)生(sheng)陰極(ji)反(fan)應,導致其(qi)腐(fu)(fu)(fu)蝕(shi)(shi)過程受到抑制;而(er)電(dian)(dian)位較負的金(jin)(jin)屬(shu)為陽(yang)極(ji),發(fa)生(sheng)陽(yang)極(ji)反(fan)應,導致其(qi)腐(fu)(fu)(fu)蝕(shi)(shi)過程加速(su)(su)。它是一種(zhong)危害極(ji)為廣(guang)泛和可能(neng)產(chan)生(sheng)嚴重(zhong)損失的腐(fu)(fu)(fu)蝕(shi)(shi)形(xing)式,廣(guang)泛地存在于船(chuan)舶、油氣、航空、建(jian)筑工業和醫(yi)療(liao)器(qi)械中(zhong)。它會(hui)(hui)造成熱(re)交換(huan)器(qi)、船(chuan)體推進(jin)器(qi)、閥門、冷凝(ning)器(qi)與醫(yi)學植入件的腐(fu)(fu)(fu)蝕(shi)(shi)失效,是一種(zhong)普遍存在的腐(fu)(fu)(fu)蝕(shi)(shi)類型(xing)。電(dian)(dian)偶(ou)(ou)腐(fu)(fu)(fu)蝕(shi)(shi)往往會(hui)(hui)誘(you)發(fa)和加速(su)(su)應力腐(fu)(fu)(fu)蝕(shi)(shi)、點(dian)蝕(shi)(shi)、縫隙腐(fu)(fu)(fu)蝕(shi)(shi)、氫脆(cui)等其(qi)他各種(zhong)類型(xing)的局部腐(fu)(fu)(fu)蝕(shi)(shi),從而(er)加速(su)(su)設備的破壞。


由于其影(ying)響因素(su)(su)比較復(fu)雜,而且任(ren)一影(ying)響因素(su)(su)的(de)改變(bian)都可能導致(zhi)更加嚴重的(de)電偶(ou)腐(fu)(fu)蝕(shi)(shi),所以對(dui)(dui)于這方面的(de)探(tan)討一直是電偶(ou)腐(fu)(fu)蝕(shi)(shi)研究的(de)一個熱點。本文從偶(ou)對(dui)(dui)材料特性,偶(ou)對(dui)(dui)幾(ji)何因素(su)(su),環(huan)境(jing)因素(su)(su)這三(san)方面出發(fa),綜(zong)述了(le)電偶(ou)腐(fu)(fu)蝕(shi)(shi)影(ying)響因素(su)(su)的(de)研究現狀,并討論了(le)電偶(ou)腐(fu)(fu)蝕(shi)(shi)研究的(de)發(fa)展(zhan)方向。


1偶對材料特(te)性的影響


不(bu)同材料(liao)間的電位(wei)差異和材料(liao)本身極化特性(xing)均對電偶腐蝕(shi)有較大的影響。


1.1電(dian)位


在(zai)腐(fu)(fu)(fu)蝕(shi)電(dian)化學中(zhong),把各種金(jin)屬(shu)在(zai)同一(yi)腐(fu)(fu)(fu)蝕(shi)介質中(zhong)所測得的(de)腐(fu)(fu)(fu)蝕(shi)電(dian)位,由低到高排(pai)列起來,形成一(yi)個電(dian)位順(shun)序(xu),即(ji)金(jin)屬(shu)腐(fu)(fu)(fu)蝕(shi)電(dian)偶(ou)(ou)序(xu)。電(dian)偶(ou)(ou)序(xu)常(chang)用于判斷(duan)不同金(jin)屬(shu)材料接(jie)觸后的(de)電(dian)偶(ou)(ou)腐(fu)(fu)(fu)蝕(shi)傾向(xiang)。在(zai)電(dian)偶(ou)(ou)腐(fu)(fu)(fu)蝕(shi)中(zhong),電(dian)位差的(de)影響(xiang)是首(shou)要(yao)的(de),電(dian)位差越大(da)腐(fu)(fu)(fu)蝕(shi)傾向(xiang)越大(da)。兩(liang)種金(jin)屬(shu)的(de)自(zi)腐(fu)(fu)(fu)蝕(shi)電(dian)位相差越大(da),其電(dian)位低的(de)金(jin)屬(shu)作為(wei)陽(yang)極(ji)越容易(yi)被腐(fu)(fu)(fu)蝕(shi),而(er)電(dian)位高的(de)金(jin)屬(shu)作為(wei)陰極(ji)則易(yi)受到保護(hu)。通常(chang)當腐(fu)(fu)(fu)蝕(shi)電(dian)位差大(da)于0.25V時(shi),產生(sheng)的(de)電(dian)偶(ou)(ou)腐(fu)(fu)(fu)蝕(shi)較嚴(yan)重(zhong),陽(yang)極(ji)金(jin)屬(shu)的(de)腐(fu)(fu)(fu)蝕(shi)損失增大(da),而(er)陰極(ji)金(jin)屬(shu)腐(fu)(fu)(fu)蝕(shi)損失減小。


研究人員對金屬(shu)的電偶序(xu)做了大量(liang)的測(ce)定工作(zuo),獲(huo)得了在流(liu)動海(hai)水(shui)、特定海(hai)域下(xia)的幾十種常用(yong)金屬(shu)的電偶序(xu)。


但它通常只列出(chu)各種(zhong)(zhong)金(jin)(jin)(jin)屬穩(wen)定電(dian)(dian)位(wei)的(de)(de)(de)相對(dui)關系,很少列出(chu)具(ju)體(ti)金(jin)(jin)(jin)屬的(de)(de)(de)穩(wen)定電(dian)(dian)位(wei)值。其主要(yao)原因(yin)是實際腐(fu)(fu)(fu)蝕(shi)(shi)(shi)介(jie)質(zhi)性(xing)質(zhi)變(bian)化(hua)很大(da)(da),測(ce)得的(de)(de)(de)電(dian)(dian)位(wei)值波動范圍也較大(da)(da),數據重現(xian)性(xing)差(cha)。再者,電(dian)(dian)偶(ou)腐(fu)(fu)(fu)蝕(shi)(shi)(shi)取(qu)決(jue)于異種(zhong)(zhong)金(jin)(jin)(jin)屬的(de)(de)(de)腐(fu)(fu)(fu)蝕(shi)(shi)(shi)電(dian)(dian)位(wei),而腐(fu)(fu)(fu)蝕(shi)(shi)(shi)電(dian)(dian)位(wei)卻與極(ji)化(hua)程(cheng)(cheng)度有關。因(yin)此,判斷(duan)金(jin)(jin)(jin)屬在偶(ou)對(dui)中的(de)(de)(de)極(ji)性(xing)和腐(fu)(fu)(fu)蝕(shi)(shi)(shi)傾(qing)向(xiang)時,電(dian)(dian)位(wei)差(cha)只決(jue)定能否發生電(dian)(dian)偶(ou)腐(fu)(fu)(fu)蝕(shi)(shi)(shi)以及腐(fu)(fu)(fu)蝕(shi)(shi)(shi)電(dian)(dian)流的(de)(de)(de)方向(xiang)等熱力(li)學(xue)性(xing)質(zhi),而實際電(dian)(dian)偶(ou)腐(fu)(fu)(fu)蝕(shi)(shi)(shi)程(cheng)(cheng)度還(huan)取(qu)決(jue)于各金(jin)(jin)(jin)屬在海(hai)水中的(de)(de)(de)極(ji)化(hua)性(xing)能等動力(li)學(xue)因(yin)素的(de)(de)(de)影響。


1.2極化特性(xing)


腐蝕電(dian)(dian)(dian)流(liu)的(de)(de)大(da)小不僅由(you)熱力學意義的(de)(de)推(tui)動(dong)力來決定(ding),還(huan)需要考(kao)慮極(ji)(ji)化(hua)(hua)行為(wei)等動(dong)力學因素。例如,海水中不銹(xiu)鋼(gang)(gang)/鋁(lv)偶對(dui)(dui)和(he)銅/鋁(lv)偶對(dui)(dui),兩者電(dian)(dian)(dian)位(wei)差(cha)接(jie)近,陰(yin)極(ji)(ji)反應均是溶解(jie)氧(yang)還(huan)原(yuan)(yuan)反應,而(er)實際過程中銅/鋁(lv)偶對(dui)(dui)的(de)(de)電(dian)(dian)(dian)偶腐蝕較(jiao)不銹(xiu)鋼(gang)(gang)/鋁(lv)的(de)(de)嚴(yan)重得多,這是因為(wei)不銹(xiu)鋼(gang)(gang)有較(jiao)大(da)的(de)(de)極(ji)(ji)化(hua)(hua)率(lv),陰(yin)極(ji)(ji)反應速(su)度很小;而(er)銅的(de)(de)極(ji)(ji)化(hua)(hua)率(lv)小,陰(yin)極(ji)(ji)反應速(su)度更大(da)[5].鈦具有很強的(de)(de)穩(wen)定(ding)的(de)(de)鈍化(hua)(hua)行為(wei),在非氧(yang)化(hua)(hua)性酸環境中與(yu)鉑(bo)偶接(jie)時,其腐蝕由(you)陰(yin)極(ji)(ji)氫離(li)子還(huan)原(yuan)(yuan)所(suo)控制,鈦此(ci)時處于(yu)活(huo)化(hua)(hua)腐蝕狀態,其電(dian)(dian)(dian)偶電(dian)(dian)(dian)位(wei)較(jiao)自腐蝕電(dian)(dian)(dian)位(wei)升(sheng)高(gao),而(er)電(dian)(dian)(dian)偶腐蝕速(su)率(lv)則較(jiao)自腐蝕速(su)率(lv)降低。


由(you)此可(ke)見,雖然電偶(ou)(ou)對的(de)陰極(ji)(ji)和陽極(ji)(ji)的(de)腐蝕電位(wei)差只(zhi)是產生(sheng)電偶(ou)(ou)腐蝕的(de)必要條件,但(dan)它(ta)并不能決定電偶(ou)(ou)腐蝕的(de)實際速(su)率(lv),即電偶(ou)(ou)腐蝕的(de)效(xiao)率(lv)。因此,分析電偶(ou)(ou)腐蝕速(su)率(lv)時還需(xu)了解偶(ou)(ou)對電極(ji)(ji)的(de)極(ji)(ji)化特性。


2偶對(dui)幾何因(yin)素的影響(xiang)


2.1陰陽極面積(ji)比


通常(chang)面(mian)(mian)積(ji)(ji)(ji)比(bi)(bi)對(dui)(dui)電(dian)(dian)(dian)偶(ou)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)行為(wei)具有(you)較大影響。在(zai)一般情況下,當陽極(ji)(ji)(ji)(ji)面(mian)(mian)積(ji)(ji)(ji)不變時,隨(sui)(sui)著陰極(ji)(ji)(ji)(ji)面(mian)(mian)積(ji)(ji)(ji)的(de)(de)(de)增(zeng)(zeng)大,陰極(ji)(ji)(ji)(ji)電(dian)(dian)(dian)流(liu)增(zeng)(zeng)加(jia)(jia),陽極(ji)(ji)(ji)(ji)金(jin)(jin)屬的(de)(de)(de)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)速度會加(jia)(jia)快。對(dui)(dui)于(yu)氫(qing)(qing)去(qu)極(ji)(ji)(ji)(ji)化來(lai)說,陰極(ji)(ji)(ji)(ji)上的(de)(de)(de)氫(qing)(qing)過電(dian)(dian)(dian)位與(yu)電(dian)(dian)(dian)流(liu)密度有(you)關(guan)。當陰極(ji)(ji)(ji)(ji)面(mian)(mian)積(ji)(ji)(ji)增(zeng)(zeng)大,相應地陰極(ji)(ji)(ji)(ji)電(dian)(dian)(dian)流(liu)密度減(jian)小,氫(qing)(qing)過電(dian)(dian)(dian)位也隨(sui)(sui)之減(jian)小,氫(qing)(qing)去(qu)極(ji)(ji)(ji)(ji)化阻力減(jian)小,陰極(ji)(ji)(ji)(ji)總電(dian)(dian)(dian)流(liu)增(zeng)(zeng)加(jia)(jia),導致陽極(ji)(ji)(ji)(ji)電(dian)(dian)(dian)流(liu)和腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)速度增(zeng)(zeng)加(jia)(jia)。對(dui)(dui)于(yu)氧(yang)去(qu)極(ji)(ji)(ji)(ji)化腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)來(lai)說,若腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)是受(shou)氧(yang)離子化過程(cheng)控制(zhi)(zhi)(zhi),同(tong)(tong)樣會由于(yu)陰極(ji)(ji)(ji)(ji)面(mian)(mian)積(ji)(ji)(ji)增(zeng)(zeng)加(jia)(jia)導致離子化電(dian)(dian)(dian)位降低,使腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)速度增(zeng)(zeng)加(jia)(jia);如果腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)過程(cheng)受(shou)氧(yang)的(de)(de)(de)擴(kuo)散控制(zhi)(zhi)(zhi),陰極(ji)(ji)(ji)(ji)面(mian)(mian)積(ji)(ji)(ji)增(zeng)(zeng)加(jia)(jia)意味著可(ke)接受(shou)更多的(de)(de)(de)氧(yang)發生還原反應,同(tong)(tong)樣也導致電(dian)(dian)(dian)偶(ou)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)速度增(zeng)(zeng)加(jia)(jia)。對(dui)(dui)于(yu)擴(kuo)散控制(zhi)(zhi)(zhi)的(de)(de)(de)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)類型(xing)(如鋼/銅,鋼/鋅(xin)等),電(dian)(dian)(dian)偶(ou)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)與(yu)陰陽極(ji)(ji)(ji)(ji)面(mian)(mian)積(ji)(ji)(ji)比(bi)(bi)的(de)(de)(de)關(guan)系遵循“集氧(yang)面(mian)(mian)積(ji)(ji)(ji)原理(li)”.但對(dui)(dui)于(yu)活化-鈍化控制(zhi)(zhi)(zhi)的(de)(de)(de)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)類型(xing)(如鈦/不銹鋼)則(ze)不存在(zai)這種關(guan)系,因為(wei)它(ta)的(de)(de)(de)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)損害還取決于(yu)金(jin)(jin)屬表面(mian)(mian)膜的(de)(de)(de)損壞,而且(qie)易造成嚴重的(de)(de)(de)局部(bu)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)。


常壓且溫度(du)較低時(shi),陽(yang)極金屬表面上(shang)的去(qu)(qu)極化劑陰極還原(yuan)反(fan)應(ying)的速(su)度(du)小(xiao)到(dao)可以(yi)忽略,而在(zai)陰極表面上(shang)則(ze)主要進(jin)行去(qu)(qu)極化劑的陰極還原(yuan)反(fan)應(ying),它(ta)的陽(yang)極溶解反(fan)應(ying)速(su)度(du)小(xiao)到(dao)可以(yi)忽略不計,根(gen)據電化學原(yuan)理,此時(shi)應(ying)滿足關系(xi)式(shi):

111.png

式中,ν為(wei)(wei)陽(yang)(yang)(yang)極(ji)(ji)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)速(su)度;陽(yang)(yang)(yang)極(ji)(ji)和(he)(he)(he)陰(yin)極(ji)(ji)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)電(dian)(dian)(dian)(dian)(dian)位分(fen)(fen)別(bie)為(wei)(wei)Ek1和(he)(he)(he)Ek2,腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)電(dian)(dian)(dian)(dian)(dian)流密度分(fen)(fen)別(bie)為(wei)(wei)Ik1和(he)(he)(he)Ik2,且Ek1<Ek2,則當(dang)它們互相接觸就組成一個腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)原電(dian)(dian)(dian)(dian)(dian)池。βa1、βc2分(fen)(fen)別(bie)為(wei)(wei)陽(yang)(yang)(yang)極(ji)(ji)和(he)(he)(he)陰(yin)極(ji)(ji)塔(ta)菲爾常數(shu)。從上式中可(ke)(ke)以看出,陰(yin)陽(yang)(yang)(yang)極(ji)(ji)面(mian)(mian)(mian)積(ji)比越大(da)(da),陽(yang)(yang)(yang)極(ji)(ji)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)速(su)度越大(da)(da)。常溫下腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)速(su)率的(de)對(dui)數(shu)與陰(yin)陽(yang)(yang)(yang)極(ji)(ji)面(mian)(mian)(mian)積(ji)比的(de)對(dui)數(shu)呈線(xian)性關(guan)系(xi)。張艷成等研究(jiu)了3.5%NaCl溶液(ye)中帶銹鑄鐵和(he)(he)(he)304不(bu)銹鋼之間(jian)的(de)電(dian)(dian)(dian)(dian)(dian)偶(ou)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)效應,得(de)出隨著(zhu)面(mian)(mian)(mian)積(ji)比增大(da)(da),電(dian)(dian)(dian)(dian)(dian)偶(ou)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)效應增大(da)(da),驗證了上述結論(lun)。但腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)速(su)率的(de)對(dui)數(shu)和(he)(he)(he)面(mian)(mian)(mian)積(ji)比對(dui)數(shu)并不(bu)都是呈線(xian)性關(guan)系(xi),可(ke)(ke)能會有極(ji)(ji)值存在(zai)。如黃桂橋等研究(jiu)了海水中鋼的(de)電(dian)(dian)(dian)(dian)(dian)偶(ou)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)指(zhi)出,當(dang)偶(ou)對(dui)的(de)電(dian)(dian)(dian)(dian)(dian)位差(cha)較(jiao)小時,在(zai)陰(yin)/陽(yang)(yang)(yang)極(ji)(ji)面(mian)(mian)(mian)積(ji)比不(bu)很大(da)(da)時,陽(yang)(yang)(yang)極(ji)(ji)的(de)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)速(su)度即達到(dao)極(ji)(ji)限(xian)值。如電(dian)(dian)(dian)(dian)(dian)位差(cha)為(wei)(wei)10mV和(he)(he)(he)20mV的(de)偶(ou)對(dui),陽(yang)(yang)(yang)極(ji)(ji)的(de)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)速(su)度分(fen)(fen)別(bie)在(zai)陰(yin)/陽(yang)(yang)(yang)極(ji)(ji)面(mian)(mian)(mian)積(ji)比為(wei)(wei)5和(he)(he)(he)20時達到(dao)極(ji)(ji)值。而偶(ou)對(dui)的(de)電(dian)(dian)(dian)(dian)(dian)位差(cha)較(jiao)大(da)(da)時,要(yao)在(zai)陰(yin)陽(yang)(yang)(yang)極(ji)(ji)面(mian)(mian)(mian)積(ji)比很大(da)(da)時,陽(yang)(yang)(yang)極(ji)(ji)的(de)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)速(su)度才能達到(dao)極(ji)(ji)限(xian)值。杜(du)敏等在(zai)研究(jiu)Q235B碳鋼/TA2鈦(tai)和(he)(he)(he)Q235B碳鋼/TA2鈦(tai)/海軍(jun)黃銅(tong)在(zai)海水中的(de)電(dian)(dian)(dian)(dian)(dian)偶(ou)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)規律時指(zhi)出,當(dang)面(mian)(mian)(mian)積(ji)比大(da)(da)于500時,陽(yang)(yang)(yang)極(ji)(ji)的(de)失重(zhong)速(su)率的(de)變化趨勢有所變緩(huan),由(you)此(ci)可(ke)(ke)推斷陽(yang)(yang)(yang)極(ji)(ji)的(de)腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)速(su)率隨著(zhu)陰(yin)陽(yang)(yang)(yang)極(ji)(ji)面(mian)(mian)(mian)積(ji)比的(de)增大(da)(da)將會有一個極(ji)(ji)限(xian)值。


2.2電偶對間距


電(dian)(dian)(dian)偶(ou)(ou)對(dui)(dui)(dui)(dui)之間(jian)的(de)(de)距(ju)離對(dui)(dui)(dui)(dui)電(dian)(dian)(dian)偶(ou)(ou)對(dui)(dui)(dui)(dui)的(de)(de)腐(fu)蝕行(xing)為也有(you)重要(yao)的(de)(de)影響。根(gen)據(ju)腐(fu)蝕電(dian)(dian)(dian)化(hua)學原理,增(zeng)大電(dian)(dian)(dian)偶(ou)(ou)對(dui)(dui)(dui)(dui)間(jian)距(ju)就是增(zeng)大了(le)帶電(dian)(dian)(dian)離子的(de)(de)擴散距(ju)離,相當于增(zeng)大溶液電(dian)(dian)(dian)阻,使電(dian)(dian)(dian)解液中的(de)(de)傳質過程受(shou)到阻礙。在(zai)給定陰陽極面積(ji)比的(de)(de)條件下,電(dian)(dian)(dian)偶(ou)(ou)對(dui)(dui)(dui)(dui)間(jian)距(ju)越大,則電(dian)(dian)(dian)偶(ou)(ou)電(dian)(dian)(dian)流密度(du)越小。Arya等在(zai)研究3%NaCl溶液中電(dian)(dian)(dian)偶(ou)(ou)對(dui)(dui)(dui)(dui)之間(jian)距(ju)離對(dui)(dui)(dui)(dui)電(dian)(dian)(dian)偶(ou)(ou)電(dian)(dian)(dian)流密度(du)的(de)(de)影響時,也證實了(le)上述結論(lun),并得出電(dian)(dian)(dian)偶(ou)(ou)對(dui)(dui)(dui)(dui)間(jian)距(ju)對(dui)(dui)(dui)(dui)電(dian)(dian)(dian)偶(ou)(ou)腐(fu)蝕影響的(de)(de)大小與(yu)介(jie)質電(dian)(dian)(dian)阻率(lv)有(you)關Song等在(zai)對(dui)(dui)(dui)(dui)AZ91D鎂合金分(fen)別(bie)與(yu)鋁合金、鐵、鋅(xin)之間(jian)的(de)(de)電(dian)(dian)(dian)偶(ou)(ou)腐(fu)蝕行(xing)為的(de)(de)研究時,也得出了(le)電(dian)(dian)(dian)偶(ou)(ou)電(dian)(dian)(dian)流密度(du)隨著與(yu)陰陽極接觸處(chu)距(ju)離的(de)(de)增(zeng)加基本呈指數分(fen)布的(de)(de)結論(lun)。


但也存在例外,趙(zhao)華萊(lai)在研究718鎳基合金鋼與(yu)VM80SS低(di)合金鋼在油氣井封(feng)隔液環境下的(de)電偶(ou)腐(fu)蝕行(xing)為(wei)時發(fa)現,試(shi)驗偶(ou)對接(jie)觸部(bu)位(wei)(wei)與(yu)遠(yuan)離接(jie)觸部(bu)位(wei)(wei)的(de)腐(fu)蝕差異并不大,分析其原因可(ke)能是陽(yang)極試(shi)樣在遠(yuan)離接(jie)觸處的(de)部(bu)位(wei)(wei)存在微電池,表面不僅發(fa)生陽(yang)極溶(rong)解反應,同時陰極過程也以較(jiao)大的(de)速度在進行(xing)。


3環(huan)境因素(su)的影響(xiang)


電(dian)解(jie)液的(de)溫度、氧含量、導電(dian)性、pH值和(he)流動狀態等介質因素也會(hui)對電(dian)偶(ou)腐蝕和(he)分布產生重要影響。


3.1溫(wen)(wen)(wen)度(du)溫(wen)(wen)(wen)度(du)對(dui)電(dian)(dian)(dian)(dian)(dian)偶(ou)腐(fu)(fu)蝕(shi)的(de)(de)(de)(de)影響是比(bi)(bi)較復雜的(de)(de)(de)(de),從動(dong)力(li)學(xue)方面考慮,溫(wen)(wen)(wen)度(du)升(sheng)高,會加速(su)熱活(huo)化過程的(de)(de)(de)(de)動(dong)力(li)學(xue),從而(er)加速(su)電(dian)(dian)(dian)(dian)(dian)化學(xue)反(fan)應(ying)速(su)度(du),使得(de)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)密度(du)增(zeng)(zeng)大(da),因此高溫(wen)(wen)(wen)條件下金屬的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)偶(ou)腐(fu)(fu)蝕(shi)帶來的(de)(de)(de)(de)破壞力(li)更大(da)。李淑(shu)英(ying)等在研(yan)究(jiu)碳(tan)鋼(gang)/紫銅在NaCl介(jie)質中的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)偶(ou)行為時(shi)指出溫(wen)(wen)(wen)度(du)對(dui)電(dian)(dian)(dian)(dian)(dian)偶(ou)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的(de)(de)(de)(de)影響非常明顯。隨(sui)溫(wen)(wen)(wen)度(du)的(de)(de)(de)(de)增(zeng)(zeng)加,電(dian)(dian)(dian)(dian)(dian)偶(ou)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)明顯增(zeng)(zeng)大(da),60℃時(shi)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)偶(ou)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)比(bi)(bi)20℃時(shi)增(zeng)(zeng)加了約(yue)5倍。Blasco等對(dui)合金及合金焊縫電(dian)(dian)(dian)(dian)(dian)偶(ou)腐(fu)(fu)蝕(shi)的(de)(de)(de)(de)研(yan)究(jiu)也(ye)表明隨(sui)溫(wen)(wen)(wen)度(du)的(de)(de)(de)(de)增(zeng)(zeng)加,電(dian)(dian)(dian)(dian)(dian)偶(ou)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)增(zeng)(zeng)大(da)。


嚴密林等模擬油(you)氣田水介質腐(fu)(fu)(fu)蝕(shi)環境研究了(le)G3油(you)管與SM80SS套管在CO2環境中的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)偶(ou)腐(fu)(fu)(fu)蝕(shi)行(xing)為(wei)(wei)。結果(guo)表(biao)明,溫(wen)度升(sheng)(sheng)高(30℃、60℃、90℃)會(hui)使電(dian)(dian)(dian)(dian)(dian)(dian)(dian)偶(ou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流增(zeng)加(jia),電(dian)(dian)(dian)(dian)(dian)(dian)(dian)偶(ou)效應(ying)增(zeng)大(da)(da)(da)。但溫(wen)度變(bian)(bian)(bian)化(hua)也會(hui)使其(qi)他環境因素(su)隨之(zhi)變(bian)(bian)(bian)化(hua),從(cong)而(er)(er)影響腐(fu)(fu)(fu)蝕(shi)。如(ru)(ru)溫(wen)度升(sheng)(sheng)高在增(zeng)加(jia)氧(yang)擴散速(su)度同時(shi)(shi)(shi)也會(hui)降低氧(yang)的(de)(de)溶解度,導(dao)致腐(fu)(fu)(fu)蝕(shi)速(su)度極(ji)(ji)大(da)(da)(da)值(zhi)現(xian)象。溫(wen)度不僅影響電(dian)(dian)(dian)(dian)(dian)(dian)(dian)偶(ou)腐(fu)(fu)(fu)蝕(shi)的(de)(de)速(su)度,有時(shi)(shi)(shi)還(huan)會(hui)改(gai)變(bian)(bian)(bian)金(jin)屬表(biao)面(mian)(mian)膜(mo)或腐(fu)(fu)(fu)蝕(shi)產(chan)物的(de)(de)結構,從(cong)而(er)(er)間(jian)接影響腐(fu)(fu)(fu)蝕(shi)過程。例如(ru)(ru),溫(wen)度變(bian)(bian)(bian)化(hua)會(hui)引起偶(ou)對的(de)(de)陰(yin)、陽極(ji)(ji)逆(ni)轉而(er)(er)改(gai)變(bian)(bian)(bian)腐(fu)(fu)(fu)蝕(shi)進程。水溶液中的(de)(de)鋼(gang)(gang)和鋅(xin)偶(ou)合后,通常(chang)鋅(xin)被腐(fu)(fu)(fu)蝕(shi),鋼(gang)(gang)被保(bao)護(hu);若(ruo)水溫(wen)高于(yu)(yu)(yu)(yu)80℃,鋼(gang)(gang)/鋅(xin)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)偶(ou)的(de)(de)極(ji)(ji)性就(jiu)會(hui)出現(xian)逆(ni)轉,鋅(xin)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)高于(yu)(yu)(yu)(yu)鋼(gang)(gang)而(er)(er)被保(bao)護(hu),鋼(gang)(gang)成為(wei)(wei)陽極(ji)(ji)而(er)(er)被腐(fu)(fu)(fu)蝕(shi)。這(zhe)是因為(wei)(wei)腐(fu)(fu)(fu)蝕(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)是非平衡電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei),易(yi)受電(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)表(biao)面(mian)(mian)反應(ying)的(de)(de)變(bian)(bian)(bian)化(hua)而(er)(er)變(bian)(bian)(bian)化(hua),當偶(ou)對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)波動大(da)(da)(da)于(yu)(yu)(yu)(yu)偶(ou)差(cha)時(shi)(shi)(shi),就(jiu)可(ke)出現(xian)極(ji)(ji)性逆(ni)轉,相應(ying)有電(dian)(dian)(dian)(dian)(dian)(dian)(dian)偶(ou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流符號改(gai)變(bian)(bian)(bian)即反向。劉東等用失重法研究二氧(yang)化(hua)碳(tan)環境中碳(tan)鋼(gang)(gang)/不銹(xiu)鋼(gang)(gang)(N80/S31803)偶(ou)對的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)偶(ou)腐(fu)(fu)(fu)蝕(shi),發現(xian)低CO2分壓(0.1MPa)時(shi)(shi)(shi)常(chang)壓下隨著溫(wen)度的(de)(de)升(sheng)(sheng)高,陽極(ji)(ji)(N80鋼(gang)(gang))的(de)(de)腐(fu)(fu)(fu)蝕(shi)速(su)率有一個極(ji)(ji)大(da)(da)(da)值(zhi)。這(zhe)是因為(wei)(wei)低于(yu)(yu)(yu)(yu)60℃時(shi)(shi)(shi),陽極(ji)(ji)腐(fu)(fu)(fu)蝕(shi)速(su)率隨溫(wen)度的(de)(de)升(sheng)(sheng)高而(er)(er)加(jia)快;溫(wen)度大(da)(da)(da)于(yu)(yu)(yu)(yu)60℃時(shi)(shi)(shi),碳(tan)鋼(gang)(gang)表(biao)面(mian)(mian)生(sheng)成了(le)FeCO3腐(fu)(fu)(fu)蝕(shi)產(chan)物沉積膜(mo),對鋼(gang)(gang)片(pian)具有一定的(de)(de)保(bao)護(hu)性。


他指出溫度主要是通(tong)過影響保護性產物膜的(de)生成來影響CO2環境中電偶腐(fu)蝕(shi)速率(lv)和腐(fu)蝕(shi)形(xing)式(shi)。


目前(qian),溫(wen)度影響的(de)研(yan)究主要集中于中、高(gao)溫(wen)段(20℃~100℃),而(er)對于實(shi)際(ji)工程中可能涉及的(de)低溫(wen)環境(如深(shen)海)的(de)電偶腐(fu)蝕(shi)研(yan)究未(wei)見報導。


3.2氧(yang)含(han)量


氧(yang)(yang)(yang)含(han)量(liang)隨環境條件的(de)(de)(de)差異會(hui)有(you)較(jiao)大幅度的(de)(de)(de)波動。對(dui)于(yu)(yu)(yu)實際腐(fu)蝕(shi)(shi)(shi)環境,不(bu)同(tong)充氣狀(zhuang)態(tai)的(de)(de)(de)影響(xiang)是(shi)存在(zai)的(de)(de)(de)。如對(dui)于(yu)(yu)(yu)開放體系(xi),空氣進入的(de)(de)(de)量(liang)相(xiang)應(ying)多些,因此氧(yang)(yang)(yang)含(han)量(liang)要相(xiang)應(ying)高些,而對(dui)于(yu)(yu)(yu)靜態(tai)深海或封閉(bi)體系(xi),氧(yang)(yang)(yang)含(han)量(liang)相(xiang)應(ying)會(hui)減(jian)小(xiao)。通(tong)常,氧(yang)(yang)(yang)是(shi)電偶腐(fu)蝕(shi)(shi)(shi)的(de)(de)(de)主要去極化劑,其含(han)量(liang)不(bu)同(tong),會(hui)對(dui)腐(fu)蝕(shi)(shi)(shi)有(you)很大影響(xiang)。對(dui)不(bu)同(tong)種類的(de)(de)(de)金(jin)(jin)屬,氧(yang)(yang)(yang)在(zai)腐(fu)蝕(shi)(shi)(shi)過程中的(de)(de)(de)作用是(shi)不(bu)同(tong)的(de)(de)(de)。如在(zai)海水介質中,對(dui)碳(tan)鋼(gang)、低合金(jin)(jin)鋼(gang)和鑄鐵等不(bu)發生(sheng)鈍化的(de)(de)(de)金(jin)(jin)屬,氧(yang)(yang)(yang)含(han)量(liang)增加,會(hui)加速陰極去極化過程,使金(jin)(jin)屬腐(fu)蝕(shi)(shi)(shi)速度增加。但對(dui)于(yu)(yu)(yu)鋁(lv)和不(bu)銹鋼(gang)等易鈍化金(jin)(jin)屬,氧(yang)(yang)(yang)含(han)量(liang)增加有(you)利于(yu)(yu)(yu)鈍化膜(mo)的(de)(de)(de)形成和修補,增強其穩定性(xing),減(jian)小(xiao)點蝕(shi)(shi)(shi)和縫蝕(shi)(shi)(shi)的(de)(de)(de)傾(qing)向(xiang)性(xing)。


氧(yang)含量對(dui)電(dian)(dian)偶(ou)腐(fu)蝕(shi)(shi)(shi)的(de)影響(xiang)是比較復(fu)雜的(de),但目前關于氧(yang)含量對(dui)電(dian)(dian)偶(ou)腐(fu)蝕(shi)(shi)(shi)影響(xiang)研究報導極(ji)少,Shalaby曾(ceng)采用(yong)通氧(yang)氣(qi)(qi)、氬氣(qi)(qi)的(de)方式模擬氧(yang)含量狀(zhuang)態(tai)研究鈦/鋁鎂(mei)合金(jin)電(dian)(dian)偶(ou)對(dui)腐(fu)蝕(shi)(shi)(shi)行(xing)為,表(biao)明(ming)(ming)通氬氣(qi)(qi)的(de)條(tiao)件下電(dian)(dian)偶(ou)腐(fu)蝕(shi)(shi)(shi)程度大大減弱(ruo)。劉冬在艦船材料電(dian)(dian)偶(ou)腐(fu)蝕(shi)(shi)(shi)機理研究時用(yong)充空氣(qi)(qi)和純氮(dan)氣(qi)(qi)分別模擬氧(yang)含量狀(zhuang)態(tai)。結(jie)果表(biao)明(ming)(ming),在充空氣(qi)(qi)條(tiao)件下,電(dian)(dian)偶(ou)電(dian)(dian)流(liu)均顯(xian)(xian)著(zhu)增(zeng)(zeng)加,電(dian)(dian)偶(ou)蝕(shi)(shi)(shi)效(xiao)應亦有所(suo)增(zeng)(zeng)加;而充氮(dan)氣(qi)(qi)條(tiao)件下電(dian)(dian)偶(ou)電(dian)(dian)流(liu)無明(ming)(ming)顯(xian)(xian)改變,與(yu)預想電(dian)(dian)偶(ou)電(dian)(dian)流(liu)應降低的(de)結(jie)果并不一致(zhi),具(ju)體原因(yin)并未(wei)作(zuo)深(shen)入討論。


3.3介質的導電性


由于(yu)金(jin)屬是(shi)良導體,而介(jie)質較(jiao)金(jin)屬具有更大(da)的電(dian)阻,局部腐蝕(shi)電(dian)流通過介(jie)質便產生電(dian)位降,形(xing)成電(dian)場分布。因(yin)(yin)此,介(jie)質的導電(dian)性(xing)是(shi)電(dian)偶腐蝕(shi)行為(wei)的最主要(yao)影響(xiang)因(yin)(yin)素(su)之一。


通常陽極(ji)(ji)金(jin)屬表(biao)(biao)面腐(fu)蝕(shi)(shi)(shi)(shi)電(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)分(fen)布是不(bu)均勻的(de)(de)(de)(de),由于(yu)溶(rong)液(ye)(ye)電(dian)(dian)(dian)阻(zu)的(de)(de)(de)(de)影響(xiang)(xiang),距(ju)離(li)偶(ou)(ou)(ou)(ou)合處越(yue)(yue)遠,腐(fu)蝕(shi)(shi)(shi)(shi)電(dian)(dian)(dian)流(liu)越(yue)(yue)小。即(ji),溶(rong)液(ye)(ye)電(dian)(dian)(dian)阻(zu)影響(xiang)(xiang)“有(you)效(xiao)(xiao)距(ju)離(li)”,電(dian)(dian)(dian)阻(zu)越(yue)(yue)大(da)則“有(you)效(xiao)(xiao)距(ju)離(li)”越(yue)(yue)小。例如,在(zai)(zai)海水中,由于(yu)電(dian)(dian)(dian)導率高(gao),兩極(ji)(ji)間(jian)溶(rong)液(ye)(ye)的(de)(de)(de)(de)電(dian)(dian)(dian)阻(zu)小,所以溶(rong)液(ye)(ye)的(de)(de)(de)(de)歐姆壓降可以忽略,電(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)有(you)效(xiao)(xiao)距(ju)離(li)可達幾十(shi)厘(li)米,電(dian)(dian)(dian)偶(ou)(ou)(ou)(ou)電(dian)(dian)(dian)流(liu)可分(fen)散(san)到離(li)接(jie)觸(chu)(chu)點較(jiao)(jiao)(jiao)遠的(de)(de)(de)(de)陽極(ji)(ji)表(biao)(biao)面,陽極(ji)(ji)所受的(de)(de)(de)(de)腐(fu)蝕(shi)(shi)(shi)(shi)較(jiao)(jiao)(jiao)“均勻”.如海船青銅螺旋槳可引(yin)起數(shu)十(shi)米遠處的(de)(de)(de)(de)鋼質(zhi)船體(ti)(ti)發生(sheng)電(dian)(dian)(dian)偶(ou)(ou)(ou)(ou)腐(fu)蝕(shi)(shi)(shi)(shi)。如果這(zhe)一偶(ou)(ou)(ou)(ou)對(dui)在(zai)(zai)普通軟水或大(da)氣中發生(sheng)電(dian)(dian)(dian)偶(ou)(ou)(ou)(ou)腐(fu)蝕(shi)(shi)(shi)(shi),由于(yu)介(jie)質(zhi)的(de)(de)(de)(de)電(dian)(dian)(dian)導率低,兩極(ji)(ji)間(jian)引(yin)起的(de)(de)(de)(de)歐姆壓降大(da),腐(fu)蝕(shi)(shi)(shi)(shi)便(bian)會集中在(zai)(zai)離(li)接(jie)觸(chu)(chu)點較(jiao)(jiao)(jiao)近(jin)的(de)(de)(de)(de)陽極(ji)(ji)表(biao)(biao)面上進行(xing),結果相(xiang)當于(yu)把陽極(ji)(ji)的(de)(de)(de)(de)有(you)效(xiao)(xiao)面積“縮小”了,使陽極(ji)(ji)表(biao)(biao)面的(de)(de)(de)(de)某些局部位(wei)置溶(rong)解速度增(zeng)大(da)。這(zhe)也(ye)是陰、陽極(ji)(ji)界(jie)面附(fu)近(jin)區域往(wang)往(wang)成為(wei)裂紋萌生(sheng)區域的(de)(de)(de)(de)原因(yin),易造成工程(cheng)事(shi)故。皇(huang)甫淑君等[21]使用掃(sao)描微電(dian)(dian)(dian)極(ji)(ji)技術研究了黃(huang)銅/16Mn鋼電(dian)(dian)(dian)偶(ou)(ou)(ou)(ou)體(ti)(ti)系在(zai)(zai)不(bu)同濃(nong)度氯化鈉(na)溶(rong)液(ye)(ye)中表(biao)(biao)面電(dian)(dian)(dian)位(wei)和電(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)分(fen)布。結果證(zheng)實,在(zai)(zai)低電(dian)(dian)(dian)導的(de)(de)(de)(de)溶(rong)液(ye)(ye)中,電(dian)(dian)(dian)偶(ou)(ou)(ou)(ou)腐(fu)蝕(shi)(shi)(shi)(shi)會集中在(zai)(zai)連接(jie)點周圍,造成嚴重的(de)(de)(de)(de)局部腐(fu)蝕(shi)(shi)(shi)(shi),隨著(zhu)溶(rong)液(ye)(ye)電(dian)(dian)(dian)導增(zeng)大(da),腐(fu)蝕(shi)(shi)(shi)(shi)分(fen)布更(geng)均勻。


3.4流動狀(zhuang)態


海(hai)水流動(dong)(dong)造(zao)成的(de)攪拌(ban)作(zuo)用因(yin)減輕或(huo)消除(chu)濃差(cha)極(ji)化而加速(su)電偶腐(fu)蝕(shi)(shi)。海(hai)水流動(dong)(dong)還(huan)可能改(gai)變(bian)充氣狀(zhuang)況或(huo)金(jin)屬(shu)表(biao)面狀(zhuang)態,從(cong)而改(gai)變(bian)腐(fu)蝕(shi)(shi)速(su)度甚至引起電偶極(ji)性的(de)逆轉。如不(bu)(bu)銹(xiu)(xiu)鋼(gang)/銅電偶對在(zai)靜止海(hai)水中由于充氣不(bu)(bu)良,不(bu)(bu)銹(xiu)(xiu)鋼(gang)處(chu)于活化狀(zhuang)態而為(wei)陽極(ji),但在(zai)流動(dong)(dong)海(hai)水中充氣良好,不(bu)(bu)銹(xiu)(xiu)鋼(gang)會處(chu)于鈍化狀(zhuang)態而成為(wei)陰極(ji)。


關于流(liu)(liu)(liu)速(su)(su)影響(xiang)腐(fu)(fu)蝕(shi)(shi)數據(ju)通(tong)常是在自然(ran)海(hai)(hai)(hai)流(liu)(liu)(liu)(0.1m/s~1m/s)條件下獲得的(de),但管道、泵(beng)以(yi)及高(gao)速(su)(su)艦船(chuan)船(chuan)體等都處在較高(gao)流(liu)(liu)(liu)速(su)(su)(5m/s~30m/s)海(hai)(hai)(hai)水中(zhong)。近年來許(xu)多研(yan)(yan)(yan)究(jiu)部門(men)相繼開展了(le)高(gao)流(liu)(liu)(liu)速(su)(su)海(hai)(hai)(hai)水中(zhong)金屬(shu)腐(fu)(fu)蝕(shi)(shi)包括電偶(ou)腐(fu)(fu)蝕(shi)(shi)的(de)研(yan)(yan)(yan)究(jiu)。戴明(ming)(ming)安等[22~24]利用高(gao)流(liu)(liu)(liu)速(su)(su)綜合測(ce)試(shi)裝置研(yan)(yan)(yan)究(jiu)了(le)從靜態(tai)海(hai)(hai)(hai)水直到(dao)11m/s的(de)流(liu)(liu)(liu)動海(hai)(hai)(hai)水中(zhong)945鋼(gang)與(yu)銅鋅(xin)合金、鈦合金、不銹鋼(gang)和鋅(xin)基(ji)犧牲陽極4種金屬(shu)偶(ou)合的(de)電偶(ou)腐(fu)(fu)蝕(shi)(shi)行為。結果(guo)表(biao)明(ming)(ming),海(hai)(hai)(hai)水流(liu)(liu)(liu)動會顯(xian)著增大(da)(da)電偶(ou)腐(fu)(fu)蝕(shi)(shi),流(liu)(liu)(liu)速(su)(su)越高(gao),電偶(ou)腐(fu)(fu)蝕(shi)(shi)作用越大(da)(da)。大(da)(da)量研(yan)(yan)(yan)究(jiu)表(biao)明(ming)(ming),電偶(ou)腐(fu)(fu)蝕(shi)(shi)對流(liu)(liu)(liu)速(su)(su)變化十分敏感(gan),電偶(ou)敏感(gan)性因子基(ji)本上與(yu)海(hai)(hai)(hai)水流(liu)(liu)(liu)速(su)(su)成正比。


除了上述主要的影響(xiang)因素(su)之外,pH值(zhi)(zhi)(zhi)也會對(dui)電(dian)偶腐蝕(shi)行(xing)為產生影響(xiang)。一(yi)般來說,當溶液pH值(zhi)(zhi)(zhi)小于4時,酸(suan)性越強,腐蝕(shi)速度(du)越大;當pH值(zhi)(zhi)(zhi)在(zai)(zai)4~9之間(jian)時,與pH值(zhi)(zhi)(zhi)幾乎無關;當pH在(zai)(zai)9~14之間(jian)時,腐蝕(shi)速度(du)大幅度(du)降低。


4電(dian)偶腐蝕研究發展方向


近年來(lai),很多(duo)研究工作者對電(dian)(dian)(dian)偶(ou)(ou)腐(fu)(fu)(fu)蝕影響(xiang)因素(su)進行(xing)了深(shen)(shen)入探討,但(dan)是(shi)仍有很多(duo)因素(su)未(wei)涉及或(huo)深(shen)(shen)入,如對低溫低氧的(de)深(shen)(shen)海環境中電(dian)(dian)(dian)偶(ou)(ou)腐(fu)(fu)(fu)蝕特性和(he)機理研究較少;流速對電(dian)(dian)(dian)偶(ou)(ou)腐(fu)(fu)(fu)蝕行(xing)為(wei)(wei)影響(xiang)較大但(dan)腐(fu)(fu)(fu)蝕機理尚不明(ming)確。隨(sui)著工程(cheng)(cheng)技術(shu)的(de)發展,全面考慮各種環境下電(dian)(dian)(dian)偶(ou)(ou)腐(fu)(fu)(fu)蝕行(xing)為(wei)(wei)是(shi)必(bi)要的(de)。目(mu)前(qian)尚沒有建立完善的(de)電(dian)(dian)(dian)偶(ou)(ou)腐(fu)(fu)(fu)蝕預測模(mo)型,隨(sui)計(ji)算機技術(shu)的(de)發展,建立各環境因素(su)作用下的(de)電(dian)(dian)(dian)偶(ou)(ou)腐(fu)(fu)(fu)蝕模(mo)型有極其(qi)重要的(de)意義(yi)。在工程(cheng)(cheng)設(she)計(ji)和(he)設(she)施制(zhi)造上不可避(bi)免的(de)會(hui)發生兩種或(huo)多(duo)種金屬(shu)電(dian)(dian)(dian)連(lian)接形成的(de)電(dian)(dian)(dian)偶(ou)(ou),由此可能產生的(de)多(duo)金屬(shu)偶(ou)(ou)合體系的(de)電(dian)(dian)(dian)偶(ou)(ou)腐(fu)(fu)(fu)蝕也(ye)是(shi)亟待(dai)解決的(de)問題(ti)。到目(mu)前(qian)為(wei)(wei)止,這方面的(de)研究幾乎為(wei)(wei)空白(bai)。


結合當前研(yan)究狀況,本文認為(wei)今(jin)后電偶腐蝕的研(yan)究工作(zuo)可(ke)能的主要發(fa)展(zhan)方向如下。


1.低溫(wen)、低氧環(huan)境(jing)下的電(dian)偶(ou)腐蝕(shi)行為研(yan)究(jiu);高流速(su)下電(dian)偶(ou)腐蝕(shi)特性及機理。溫(wen)度、溶解氧、面積比等各(ge)因(yin)素發(fa)生(sheng)變化時,某些電(dian)偶(ou)對(dui)可能(neng)發(fa)生(sheng)極(ji)性逆(ni)轉(zhuan),會導(dao)致(zhi)腐蝕(shi)較輕的陰(yin)極(ji)突然加速(su)腐蝕(shi),是一種潛在危害。環(huan)境(jing)因(yin)素如(ru)何影(ying)響極(ji)性逆(ni)轉(zhuan)和(he)極(ji)性逆(ni)轉(zhuan)的機理需(xu)要進行深入系統的研(yan)究(jiu)。


2.完善現(xian)有的陰陽極(ji)面積比電(dian)偶(ou)腐蝕模型,采用(yong)復(fu)雜數(shu)據處理技(ji)術及(ji)計算機軟件技(ji)術建立包括溫度、氧含量(liang)等(deng)各種(zhong)環境因素作用(yong)的電(dian)偶(ou)腐蝕預(yu)測模型。


3.為全面考慮電偶(ou)腐蝕(shi)的(de)影響,以保(bao)障工程設計可靠性和性能,開(kai)展多金屬復雜偶(ou)合(he)體系腐蝕(shi)行為研究,應是下一(yi)步電偶(ou)腐蝕(shi)研究工作的(de)重點內容。

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