公路(lu)鋼橋(qiao)是目前(qian)現代(dai)社(she)會(hui)應(ying)用(yong)廣泛的橋(qiao)梁(liang)(liang)之一(yi)，由于公路(lu)橋(qiao)梁(liang)(liang)的受力狀(zhuang)況和(he)(he)服役(yi)環境的不同，Q345q在國內應(ying)用(yong)極為廣泛[1,2]。但是，鋼鐵材(cai)料在軋(ya)制過(guo)程中(zhong)處于高(gao)溫狀(zhuang)態，暴露于空(kong)氣中(zhong)表面會(hui)形成一(yi)層氧(yang)(yang)化(hua)皮(pi)，氧(yang)(yang)化(hua)皮(pi)的組成和(he)(he)結(jie)構(gou)對(dui)鋼材(cai)在貯(zhu)存(cun)、運輸和(he)(he)使用(yong)過(guo)程中(zhong)的耐大(da)氣腐蝕性能起著重要作(zuo)用(yong)[3,4]。因此，如(ru)何提高(gao)熱軋(ya)帶鋼表面氧(yang)(yang)化(hua)皮(pi)的質量和(he)(he)耐大(da)氣腐蝕性能成為亟待解決的問題。

國內外研(yan)(yan)(yan)究(jiu)(jiu)者對(dui)(dui)(dui)(dui)氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)結構(gou)及(ji)其腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)行(xing)為(wei)做了(le)(le)(le)系統的(de)(de)(de)(de)(de)(de)(de)(de)(de)研(yan)(yan)(yan)究(jiu)(jiu)。韓軍科等(deng)(deng)[5]研(yan)(yan)(yan)究(jiu)(jiu)了(le)(le)(le)耐候鋼(gang)(gang)表(biao)(biao)面氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)結構(gou)及(ji)其對(dui)(dui)(dui)(dui)大(da)氣腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)行(xing)為(wei)的(de)(de)(de)(de)(de)(de)(de)(de)(de)影(ying)響，發(fa)(fa)(fa)現(xian)相對(dui)(dui)(dui)(dui)于(yu)裸(luo)鋼(gang)(gang)，氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)明(ming)(ming)顯減(jian)緩了(le)(le)(le)鋼(gang)(gang)的(de)(de)(de)(de)(de)(de)(de)(de)(de)初期腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)，氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)越(yue)致密，對(dui)(dui)(dui)(dui)基體的(de)(de)(de)(de)(de)(de)(de)(de)(de)保護作(zuo)(zuo)用(yong)(yong)越(yue)強；但對(dui)(dui)(dui)(dui)于(yu)長期腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)而言，氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)存在(zai)(zai)反(fan)而促進腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)，因為(wei)在(zai)(zai)腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)過(guo)程中(zhong)(zhong)，氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)表(biao)(biao)面逐漸(jian)生成(cheng)銹(xiu)層，部分未(wei)轉(zhuan)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)的(de)(de)(de)(de)(de)(de)(de)(de)(de)氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)作(zuo)(zuo)為(wei)銹(xiu)層中(zhong)(zhong)的(de)(de)(de)(de)(de)(de)(de)(de)(de)雜質(zhi)和(he)缺陷加(jia)速(su)(su)鋼(gang)(gang)的(de)(de)(de)(de)(de)(de)(de)(de)(de)腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)。Dong等(deng)(deng)[6]研(yan)(yan)(yan)究(jiu)(jiu)了(le)(le)(le)熱(re)軋(ya)帶鋼(gang)(gang)表(biao)(biao)面氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)在(zai)(zai)NaCl溶液中(zhong)(zhong)的(de)(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)學腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)行(xing)為(wei)，發(fa)(fa)(fa)現(xian)腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)初期氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)發(fa)(fa)(fa)生溶解被還原(yuan)，導(dao)致電(dian)(dian)(dian)(dian)極(ji)活性(xing)(xing)(xing)和(he)腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)速(su)(su)率(lv)增(zeng)大(da)，腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)后(hou)期有(you)(you)不溶性(xing)(xing)(xing)的(de)(de)(de)(de)(de)(de)(de)(de)(de)腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)產物沉積于(yu)表(biao)(biao)面，導(dao)致電(dian)(dian)(dian)(dian)極(ji)電(dian)(dian)(dian)(dian)阻增(zeng)大(da)，從(cong)而減(jian)小腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)速(su)(su)率(lv)。Collazo等(deng)(deng)[7]研(yan)(yan)(yan)究(jiu)(jiu)了(le)(le)(le)低碳(tan)鋼(gang)(gang)表(biao)(biao)面氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)學腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)行(xing)為(wei)，發(fa)(fa)(fa)現(xian)氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)存在(zai)(zai)明(ming)(ming)顯減(jian)小腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)速(su)(su)率(lv)。Chattopadhyay等(deng)(deng)[8]等(deng)(deng)通過(guo)拉曼光譜研(yan)(yan)(yan)究(jiu)(jiu)了(le)(le)(le)熱(re)軋(ya)帶鋼(gang)(gang)的(de)(de)(de)(de)(de)(de)(de)(de)(de)氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)組成(cheng)結構(gou)，表(biao)(biao)明(ming)(ming)含(han)(han)有(you)(you)大(da)量缺陷的(de)(de)(de)(de)(de)(de)(de)(de)(de)氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)會加(jia)速(su)(su)腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)。張華民(min)等(deng)(deng)[9,10]的(de)(de)(de)(de)(de)(de)(de)(de)(de)研(yan)(yan)(yan)究(jiu)(jiu)工作(zuo)(zuo)表(biao)(biao)明(ming)(ming)，在(zai)(zai)含(han)(han)有(you)(you)Cl-的(de)(de)(de)(de)(de)(de)(de)(de)(de)中(zhong)(zhong)性(xing)(xing)(xing)環境中(zhong)(zhong)，表(biao)(biao)面帶有(you)(you)氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)會引(yin)起局部腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)，主要是(shi)因為(wei)Cl-的(de)(de)(de)(de)(de)(de)(de)(de)(de)入侵破壞了(le)(le)(le)氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)完整(zheng)性(xing)(xing)(xing)和(he)致密性(xing)(xing)(xing)；并在(zai)(zai)穩態(tai)(tai)電(dian)(dian)(dian)(dian)位和(he)靜態(tai)(tai)掛片(pian)實(shi)(shi)驗時發(fa)(fa)(fa)現(xian)，Cl-會在(zai)(zai)氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)缺陷處(chu)形成(cheng)點蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)核，造成(cheng)點蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)坑，導(dao)致碳(tan)鋼(gang)(gang)與(yu)氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)之間(jian)形成(cheng)電(dian)(dian)(dian)(dian)偶電(dian)(dian)(dian)(dian)池，從(cong)而在(zai)(zai)缺陷處(chu)產生嚴重的(de)(de)(de)(de)(de)(de)(de)(de)(de)局部腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)。周賢良等(deng)(deng)[11]采(cai)用(yong)(yong)干濕(shi)周期浸潤實(shi)(shi)驗研(yan)(yan)(yan)究(jiu)(jiu)了(le)(le)(le)不同氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)結構(gou)的(de)(de)(de)(de)(de)(de)(de)(de)(de)510L熱(re)軋(ya)帶鋼(gang)(gang)在(zai)(zai)0.01 mol/L的(de)(de)(de)(de)(de)(de)(de)(de)(de)NaHSO3溶液中(zhong)(zhong)腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)行(xing)為(wei)，表(biao)(biao)明(ming)(ming)在(zai)(zai)氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)連(lian)續致密的(de)(de)(de)(de)(de)(de)(de)(de)(de)情況下，氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)越(yue)厚，對(dui)(dui)(dui)(dui)鋼(gang)(gang)基體的(de)(de)(de)(de)(de)(de)(de)(de)(de)耐蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)性(xing)(xing)(xing)影(ying)響越(yue)大(da)。何愛(ai)花[12]對(dui)(dui)(dui)(dui)熱(re)軋(ya)鋼(gang)(gang)板(ban)表(biao)(biao)面氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)膜對(dui)(dui)(dui)(dui)基體鋼(gang)(gang)板(ban)腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)行(xing)為(wei)的(de)(de)(de)(de)(de)(de)(de)(de)(de)影(ying)響進行(xing)了(le)(le)(le)研(yan)(yan)(yan)究(jiu)(jiu)，表(biao)(biao)明(ming)(ming)氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)只起到物理屏(ping)蔽的(de)(de)(de)(de)(de)(de)(de)(de)(de)作(zuo)(zuo)用(yong)(yong)，對(dui)(dui)(dui)(dui)金屬的(de)(de)(de)(de)(de)(de)(de)(de)(de)陽(yang)極(ji)反(fan)應(ying)和(he)陰極(ji)反(fan)應(ying)不產生影(ying)響，只有(you)(you)在(zai)(zai)缺氧(yang)(yang)(yang)(yang)(yang)條件下氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)參與(yu)陰極(ji)還原(yuan)過(guo)程，腐(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)(shi)(shi)性(xing)(xing)(xing)離子穿(chuan)過(guo)氧(yang)(yang)(yang)(yang)(yang)化(hua)(hua)(hua)(hua)(hua)(hua)(hua)(hua)皮(pi)(pi)(pi)(pi)(pi)(pi)的(de)(de)(de)(de)(de)(de)(de)(de)(de)孔隙導(dao)致基體溶解。

諸(zhu)多(duo)工作表明，氧(yang)化(hua)(hua)皮(pi)(pi)(pi)的(de)(de)存(cun)在，對(dui)(dui)鋼(gang)(gang)(gang)基(ji)體的(de)(de)腐(fu)(fu)蝕(shi)(shi)或(huo)(huo)多(duo)或(huo)(huo)少具有(you)(you)(you)延(yan)緩作用。然(ran)而，對(dui)(dui)帶(dai)氧(yang)化(hua)(hua)皮(pi)(pi)(pi)鋼(gang)(gang)(gang)的(de)(de)腐(fu)(fu)蝕(shi)(shi)行為研(yan)究(jiu)大多(duo)集中在Cl-等(deng)單(dan)一介(jie)質(zhi)中，對(dui)(dui)熱軋(ya)氧(yang)化(hua)(hua)皮(pi)(pi)(pi)的(de)(de)破(po)壞(huai)機理(li)、帶(dai)氧(yang)化(hua)(hua)皮(pi)(pi)(pi)鋼(gang)(gang)(gang)的(de)(de)腐(fu)(fu)蝕(shi)(shi)機理(li)及銹層形成機理(li)的(de)(de)研(yan)究(jiu)更是鮮有(you)(you)(you)報道，不能完全說明帶(dai)氧(yang)化(hua)(hua)皮(pi)(pi)(pi)鋼(gang)(gang)(gang)的(de)(de)腐(fu)(fu)蝕(shi)(shi)行為。鋼(gang)(gang)(gang)服(fu)役過程(cheng)中的(de)(de)腐(fu)(fu)蝕(shi)(shi)是在苛刻交替環(huan)境下發生的(de)(de)[13]，我(wo)國(guo)西(xi)(xi)北(bei)(bei)地區橋梁鋼(gang)(gang)(gang)的(de)(de)腐(fu)(fu)蝕(shi)(shi)主要受Cl-（冬(dong)季除(chu)雪(xue)劑）、SO2（工業大氣(qi)）、濕度、溫度等(deng)因(yin)素的(de)(de)影響，其干旱大氣(qi)含(han)鹽環(huan)境獨特(te)[14]。因(yin)此，本論文選擇除(chu)冰(bing)鹽、NaHSO3、除(chu)冰(bing)鹽+NaHSO3三種腐(fu)(fu)蝕(shi)(shi)介(jie)質(zhi)模(mo)擬(ni)西(xi)(xi)北(bei)(bei)大氣(qi)的(de)(de)幾個(ge)典型腐(fu)(fu)蝕(shi)(shi)環(huan)境，著重研(yan)究(jiu)了氧(yang)化(hua)(hua)皮(pi)(pi)(pi)在不同介(jie)質(zhi)下的(de)(de)破(po)壞(huai)機理(li)和帶(dai)氧(yang)化(hua)(hua)皮(pi)(pi)(pi)鋼(gang)(gang)(gang)的(de)(de)腐(fu)(fu)蝕(shi)(shi)機理(li)，有(you)(you)(you)助于(yu)對(dui)(dui)熱軋(ya)氧(yang)化(hua)(hua)皮(pi)(pi)(pi)鋼(gang)(gang)(gang)腐(fu)(fu)蝕(shi)(shi)行為和機理(li)的(de)(de)認識(shi)，希望從熱軋(ya)源頭改善氧(yang)化(hua)(hua)皮(pi)(pi)(pi)的(de)(de)保護性。

1 實驗方法

1.1 實驗材料(liao)

實驗材料為某(mou)大型(xing)鋼(gang)廠煉制的Q345q橋梁鋼(gang)，經過控(kong)(kong)軋控(kong)(kong)冷(leng)后(hou)，軋制成(cheng)(cheng)8 mm厚的鋼(gang)板，氧化(hua)后(hou)上下(xia)表面帶有氧化(hua)皮。Q345q鋼(gang)的化(hua)學成(cheng)(cheng)分(fen)見表1。

將上述鋼(gang)板用(yong)(yong)線切(qie)割機切(qie)取以下兩(liang)種規(gui)格：40 mm×40 mm×8 mm，數量(liang)9個，用(yong)(yong)于腐(fu)蝕增重測(ce)量(liang)和(he)宏觀(guan)腐(fu)蝕形貌(mao)觀(guan)察(cha)；10 mm×10 mm×8 mm，3個用(yong)(yong)于氧化皮及銹層(ceng)表(biao)面(mian)(mian)(mian)和(he)截面(mian)(mian)(mian)微(wei)觀(guan)腐(fu)蝕形貌(mao)的(de)觀(guan)察(cha)，3個用(yong)(yong)于XRD物相分(fen)析和(he)電化學實驗。切(qie)完試樣后(hou)，保留40 mm×40 mm和(he)10 mm×10 mm的(de)工(gong)(gong)作面(mian)(mian)(mian)進(jin)行腐(fu)蝕實驗，其余非(fei)工(gong)(gong)作面(mian)(mian)(mian)用(yong)(yong)環氧樹(shu)脂(zhi)包裹，待環氧樹(shu)脂(zhi)完全干燥后(hou)，將工(gong)(gong)作面(mian)(mian)(mian)先用(yong)(yong)丙酮除油，然后(hou)用(yong)(yong)無水乙醇和(he)蒸餾水清洗用(yong)(yong)冷風吹干。

1.2 室內加速腐(fu)蝕實驗

模(mo)擬西北大氣(qi)幾(ji)個典型腐(fu)(fu)蝕(shi)(shi)環境(jing)的(de)腐(fu)(fu)蝕(shi)(shi)液(ye)(ye)(ye)(ye)為除冰鹽溶(rong)(rong)(rong)液(ye)(ye)(ye)(ye)（根據GB19746-2005《金屬和合(he)金的(de)腐(fu)(fu)蝕(shi)(shi)鹽溶(rong)(rong)(rong)液(ye)(ye)(ye)(ye)周(zhou)浸(jin)試驗(yan)(yan)》配置(zhi)，溶(rong)(rong)(rong)液(ye)(ye)(ye)(ye)pH=9±0.2）、0.01 mol/LNaHSO3溶(rong)(rong)(rong)液(ye)(ye)(ye)(ye)（根據TB/T2375-1993《鐵路用耐候鋼(gang)周(zhou)期浸(jin)潤(run)腐(fu)(fu)蝕(shi)(shi)試驗(yan)(yan)方法》配置(zhi)，溶(rong)(rong)(rong)液(ye)(ye)(ye)(ye)pH=4.4±0.2）、除冰鹽+0.01 mol/LNaHSO3溶(rong)(rong)(rong)液(ye)(ye)(ye)(ye)（溶(rong)(rong)(rong)液(ye)(ye)(ye)(ye)pH=4.8±0.2），所(suo)有(you)成分(fen)如表(biao)2所(suo)示(shi)。本文通過干(gan)濕(shi)交(jiao)替加(jia)速腐(fu)(fu)蝕(shi)(shi)實(shi)驗(yan)(yan)模(mo)擬西北大氣(qi)三(san)個典型環境(jing)中(zhong)的(de)腐(fu)(fu)蝕(shi)(shi)過程，具體(ti)實(shi)驗(yan)(yan)方法是：用分(fen)析(xi)天(tian)平稱(cheng)取初始質(zhi)量(liang)（精度0.0001 g），每12 h在(zai)試樣工作(zuo)(zuo)面(mian)滴加(jia)腐(fu)(fu)蝕(shi)(shi)液(ye)(ye)(ye)(ye)（一天(tian)兩次(ci)），滴加(jia)的(de)溶(rong)(rong)(rong)液(ye)(ye)(ye)(ye)量(liang)按40 μL/cm2計算，每2 d取出樣品稱(cheng)重，取樣時間：24、72、144、288、480 h，實(shi)驗(yan)(yan)總(zong)共進行(xing)20 d。本實(shi)驗(yan)(yan)在(zai)恒(heng)(heng)溫(wen)(wen)(wen)恒(heng)(heng)濕(shi)試驗(yan)(yan)箱中(zhong)進行(xing)，溫(wen)(wen)(wen)度30±2℃，相對濕(shi)度60±5RH。每次(ci)滴加(jia)溶(rong)(rong)(rong)液(ye)(ye)(ye)(ye)之前，用蒸餾水沖(chong)洗工作(zuo)(zuo)表(biao)面(mian)，避免鹽分(fen)累(lei)積。每次(ci)稱(cheng)重前在(zai)真空干(gan)燥(zao)(zao)箱中(zhong)進行(xing)干(gan)燥(zao)(zao)處理2 h，干(gan)燥(zao)(zao)溫(wen)(wen)(wen)度50℃。

1.3 銹層(ceng)物相(xiang)與形貌(mao)觀察

采(cai)用Rigaku Ultima IV X-射線衍射儀（XRD）對氧化(hua)皮(pi)原樣及在三種(zhong)介質中(zhong)腐蝕不同時間的銹層(ceng)進行分析，通過HighScore Plus3.0軟件檢索(suo)物相(xiang)，每種(zhong)物相(xiang)的質量分數可以由各個(ge)物相(xiang)的RIR（Reference intensity ratio）值確(que)定(ding)，即采(cai)用參比(bi)強度法(fa)進行半定(ding)量分析。靶(ba)材為(wei)(wei)Cu靶(ba)，管電壓為(wei)(wei)40 kV，掃描速率為(wei)(wei)4°/min，掃描范(fan)圍為(wei)(wei)10°~80°。用數碼相(xiang)機和FEG-450冷(leng)場發射掃描電子顯微(wei)鏡（SEM）對氧化(hua)皮(pi)銹層(ceng)表面宏觀(guan)形貌(mao)、微(wei)觀(guan)形貌(mao)及銹層(ceng)截面形貌(mao)觀(guan)察分析。

1.4 電化(hua)學實(shi)驗

電(dian)化(hua)學實驗采(cai)用的(de)上海(hai)辰華CHI660e電(dian)化(hua)學工作站三電(dian)極(ji)系統，Pt電(dian)極(ji)為(wei)(wei)輔助電(dian)極(ji)，飽和甘(gan)汞電(dian)極(ji)（SCE）為(wei)(wei)參(can)比電(dian)極(ji)，10 mm×10 mm試樣的(de)帶銹面為(wei)(wei)工作電(dian)極(ji)，考慮到三種介質都(dou)含有SO32-離子，電(dian)解(jie)液(ye)采(cai)用0.1 mol/L的(de)Na2SO4溶液(ye)，在(zai)恒溫(wen)水浴鍋中將溫(wen)度維(wei)持在(zai)30±2℃。測(ce)量(liang)極(ji)化(hua)曲線的(de)掃描(miao)速率為(wei)(wei)0.5 mV/s，測(ce)量(liang)范圍為(wei)(wei)-1.5~1 V。

2 實驗結果

2.1 帶氧化皮(pi)試樣的腐蝕動(dong)力學

帶氧化皮Q345q鋼在(zai)(zai)模擬西北大氣幾個典型環境(jing)中(zhong)(zhong)的(de)腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)動力學曲(qu)線(xian)如(ru)圖1所示。圖1a可見，在(zai)(zai)三種介(jie)(jie)質(zhi)中(zhong)(zhong)的(de)腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)增重都隨時(shi)間(jian)(jian)(jian)的(de)延(yan)長(chang)而增大，且增重大小順序為：NaHSO3>混合溶(rong)液>除冰(bing)(bing)鹽(yan)。圖1b是腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)速(su)(su)(su)率曲(qu)線(xian)，腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)初期，在(zai)(zai)除冰(bing)(bing)鹽(yan)介(jie)(jie)質(zhi)中(zhong)(zhong)的(de)腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)速(su)(su)(su)率最低，速(su)(su)(su)率曲(qu)線(xian)幾乎呈直(zhi)線(xian)；在(zai)(zai)NaHSO3單(dan)獨存在(zai)(zai)介(jie)(jie)質(zhi)中(zhong)(zhong)的(de)腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)速(su)(su)(su)率明顯大于(yu)(yu)在(zai)(zai)除冰(bing)(bing)鹽(yan)介(jie)(jie)質(zhi)中(zhong)(zhong)的(de)。當NaHSO3+除冰(bing)(bing)鹽(yan)同時(shi)存在(zai)(zai)時(shi)，腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)速(su)(su)(su)率介(jie)(jie)于(yu)(yu)兩者(zhe)之(zhi)間(jian)(jian)(jian)，這說明NaHSO3和除冰(bing)(bing)鹽(yan)之(zhi)間(jian)(jian)(jian)存在(zai)(zai)協同效應，但腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)速(su)(su)(su)率并不是兩者(zhe)的(de)簡(jian)單(dan)加和。隨著腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)時(shi)間(jian)(jian)(jian)進行至192 h，在(zai)(zai)除冰(bing)(bing)鹽(yan)介(jie)(jie)質(zhi)和NaHSO3+除冰(bing)(bing)鹽(yan)介(jie)(jie)質(zhi)中(zhong)(zhong)的(de)腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)速(su)(su)(su)率都呈現增大趨勢，腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)介(jie)(jie)質(zhi)對Q345q鋼腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)速(su)(su)(su)率的(de)影響(xiang)順序為：NaHSO3>混合溶(rong)液>除冰(bing)(bing)鹽(yan)。通常，鋼的(de)大氣腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)規(gui)律(lv)(lv)符合冪函數規(gui)律(lv)(lv)[15,16,17]：

其中，ΔW為單(dan)位(wei)面積(ji)的腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)增重(zhong)（mg·cm-2），t為腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)時間(jian)（h），A和n為與腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)特性有(you)(you)關的常(chang)數。n值(zhi)的大小反映了腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)發展趨勢，n>1，腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)過(guo)程加速(su)(su)，銹(xiu)層(ceng)(ceng)不(bu)具保(bao)護性；n<1，腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)過(guo)程減速(su)(su)，銹(xiu)層(ceng)(ceng)有(you)(you)保(bao)護性。有(you)(you)學者(zhe)[18]提出了利用線性回歸分析腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)數據的方(fang)(fang)法，通過(guo)取(qu)對數在腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)失(shi)重(zhong)-腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)時間(jian)曲線上得到直線，這種(zhong)方(fang)(fang)法不(bu)僅(jin)可以有(you)(you)效地研(yan)究腐(fu)(fu)(fu)(fu)(fu)蝕(shi)(shi)規律，而且對動力學的深入研(yan)究非常(chang)重(zhong)要，因此（1）式寫成對數的形式為：

為(wei)了(le)驗證鋼在三(san)種(zhong)介(jie)(jie)質(zhi)中(zhong)(zhong)的腐(fu)蝕(shi)動力(li)學發展規(gui)律(lv)，利(li)用該(gai)函數對(dui)腐(fu)蝕(shi)增重(zhong)數據進行擬合(he)，擬合(he)結果(guo)如圖(tu)(tu)2所(suo)示(shi)。從圖(tu)(tu)中(zhong)(zhong)可看出，腐(fu)蝕(shi)過程被(bei)分為(wei)了(le)兩(liang)個階段。在除冰鹽(yan)介(jie)(jie)質(zhi)中(zhong)(zhong)192 h以下，腐(fu)蝕(shi)處于“潛伏期”，腐(fu)蝕(shi)增重(zhong)幾乎(hu)(hu)沒有(you)變化，n<1說明腐(fu)蝕(shi)速(su)率(lv)減緩，氧化皮對(dui)基體有(you)一(yi)定的保護作用；192 h后(hou)腐(fu)蝕(shi)速(su)率(lv)快速(su)呈(cheng)(cheng)指數規(gui)律(lv)增大(da)(da)，表現(xian)為(wei)n值(zhi)大(da)(da)于1，可能是因(yin)為(wei)氧化皮被(bei)破壞；在NaHSO3溶(rong)(rong)液(ye)中(zhong)(zhong)，48 h已發生(sheng)腐(fu)蝕(shi)，在48 h~96 h之間(jian)時n<1，腐(fu)蝕(shi)速(su)率(lv)有(you)所(suo)降(jiang)低；96 h后(hou)腐(fu)蝕(shi)速(su)率(lv)呈(cheng)(cheng)線性規(gui)律(lv)增大(da)(da)，其可能原因(yin)為(wei)氧化皮逐漸被(bei)溶(rong)(rong)解(jie)。在除冰鹽(yan)+NaHSO3溶(rong)(rong)液(ye)中(zhong)(zhong)，在48 h~144 h之間(jian)的n=0.9343<1，腐(fu)蝕(shi)速(su)率(lv)幾乎(hu)(hu)不變；144 h后(hou)腐(fu)蝕(shi)速(su)率(lv)緩慢增大(da)(da)，且n值(zhi)介(jie)(jie)于在兩(liang)種(zhong)單(dan)相(xiang)介(jie)(jie)質(zhi)中(zhong)(zhong)的之間(jian)，說明除冰鹽(yan)和NaHSO3存在協同作用。

圖1   帶氧化皮Q345q鋼在三種不同溶液(ye)中的腐(fu)蝕動力學曲線

圖2   腐(fu)蝕動力(li)學雙(shuang)對(dui)數(shu)擬合曲線

2.2 氧化皮及銹層物(wu)相(xiang)分析

圖3為帶氧化皮(pi)Q345q鋼原始樣及在三種西北典型(xing)大氣環境模擬液中腐蝕不(bu)同時間的(de)銹層XRD譜圖。由圖3a可(ke)知，Q345q鋼經1069℃和(he)776℃的(de)開軋(ya)(ya)溫度和(he)終(zhong)軋(ya)(ya)溫度熱軋(ya)(ya)后(hou)氧化皮(pi)的(de)物(wu)相組成主要是Fe2O3和(he)Fe3O4。

由圖3b看出，在(zai)(zai)除冰(bing)鹽(yan)介(jie)質中的(de)(de)腐蝕產物(wu)(wu)主要由β-FeOOH、γ-FeOOH、α-FeOOH、Fe2O3、Fe3O4、氯(lv)化(hua)(hua)物(wu)(wu)組成。從(cong)特(te)征峰的(de)(de)強(qiang)度(du)(du)看，β-FeOOH的(de)(de)物(wu)(wu)相(xiang)(xiang)峰（11.84°）隨(sui)腐蝕時(shi)間的(de)(de)延(yan)(yan)長而增(zeng)(zeng)強(qiang)，同時(shi)疊加(jia)(jia)了(le)氯(lv)化(hua)(hua)物(wu)(wu)的(de)(de)峰，此氯(lv)化(hua)(hua)物(wu)(wu)為HFeCl4（H2O）6（JCPDS 78-1929），它是(shi)一種中間化(hua)(hua)合物(wu)(wu)，在(zai)(zai)干的(de)(de)階(jie)段發(fa)生(sheng)(sheng)氯(lv)化(hua)(hua)物(wu)(wu)→β-FeOOH物(wu)(wu)相(xiang)(xiang)轉變(bian)(bian)[19]，它的(de)(de)特(te)征峰強(qiang)度(du)(du)（30.82°）有所減(jian)小，說(shuo)明部分氯(lv)化(hua)(hua)物(wu)(wu)在(zai)(zai)整個過程中發(fa)生(sheng)(sheng)了(le)轉化(hua)(hua)；γ-FeOOH的(de)(de)特(te)征峰（14.14°）在(zai)(zai)72 h后(hou)，隨(sui)腐蝕時(shi)間的(de)(de)延(yan)(yan)長增(zeng)(zeng)加(jia)(jia)較少；α-FeOOH的(de)(de)特(te)征峰（21.22°）在(zai)(zai)整個腐蝕過程中變(bian)(bian)化(hua)(hua)不明顯，甚至(zhi)在(zai)(zai)480 h后(hou)峰強(qiang)仍然較低，說(shuo)明只有少量(liang)γ-FeOOH和(he)β-FeOOH轉化(hua)(hua)成了(le)α-FeOOH；Fe2O3（33.18°）和(he)Fe3O4（35.43°）的(de)(de)特(te)征峰隨(sui)時(shi)間的(de)(de)延(yan)(yan)長逐漸減(jian)小，說(shuo)明部分氧化(hua)(hua)皮發(fa)生(sheng)(sheng)了(le)溶解(jie)或脫落。

由圖3c可看出，NaHSO3溶(rong)液中(zhong)的(de)腐(fu)蝕(shi)產物主(zhu)要由γ-FeOOH、α-FeOOH、Fe2O3、Fe3O4組成。γ-FeOOH（14.14°）和α-FeOOH（21.22°）的(de)峰強隨(sui)時間的(de)延長增大(da)，說(shuo)(shuo)明整(zheng)個(ge)過程中(zhong)發生(sheng)了γ-FeOOH→α-FeOOH的(de)轉(zhuan)化(hua)，但轉(zhuan)化(hua)不完全(quan)；Fe2O3（33.18°）和Fe3O4（35.43°）的(de)特征峰強在24 h~144 h之間變化(hua)很小，直至288 h后(hou)強度逐漸減小，這說(shuo)(shuo)明在干濕循環的(de)濕的(de)階段發生(sheng)了γ-FeOOH的(de)還原生(sheng)成了Fe3O4[20]，補償了腐(fu)蝕(shi)前期(qi)部(bu)分脫落或溶(rong)解的(de)氧(yang)化(hua)皮，腐(fu)蝕(shi)后(hou)期(qi)氧(yang)化(hua)皮的(de)斷裂(lie)強度已不能抵抗銹層內(nei)腐(fu)蝕(shi)應力(li)發生(sheng)了破(po)裂(lie)和溶(rong)解。

圖3   氧化(hua)皮(pi)原始樣及帶氧化(hua)皮(pi)試(shi)樣在三種溶(rong)液(ye)中腐蝕不同時間的XRD譜圖

由圖(tu)3d看出，在除(chu)冰(bing)鹽(yan)+ NaHSO3介(jie)質中(zhong)的(de)腐蝕產物(wu)(wu)的(de)種類與除(chu)冰(bing)鹽(yan)介(jie)質中(zhong)的(de)一(yi)致，但是Fe2O3（33.18°）和Fe3O4（35.43°）的(de)特(te)征峰強明(ming)顯(xian)減小(xiao)，說明(ming)Cl-和HSO3-之間存在協同效(xiao)應加(jia)速了(le)(le)氧化(hua)皮的(de)溶解：Fe3O4+8H++2e-→3Fe2++4H2O；氯(lv)化(hua)物(wu)(wu)HFeCl4（H2O）6（30.82°）的(de)峰強先增(zeng)大(da)后減小(xiao)，β-FeOOH的(de)主峰上也疊加(jia)了(le)(le)此(ci)氯(lv)化(hua)物(wu)(wu)的(de)峰，說明(ming)氯(lv)化(hua)物(wu)(wu)發生了(le)(le)不(bu)完全轉(zhuan)化(hua)；γ-FeOOH和α-FeOOH的(de)峰強與除(chu)冰(bing)鹽(yan)介(jie)質中(zhong)的(de)變(bian)化(hua)一(yi)致。

表(biao)3為三種(zhong)介質(zhi)中腐蝕480 h的(de)銹(xiu)層(ceng)物(wu)相(xiang)的(de)相(xiang)對含量(liang)及α/γ*的(de)值，用α/γ*來評價(jia)銹(xiu)層(ceng)的(de)保(bao)護(hu)性[21,22,23]，α/γ*表(biao)示(shi)α/（γ+β+Mgn），α、γ、β、Mgn分別為α-FeOOH、γ-FeOOH、β-FeOOH、Fe3O4。通(tong)過比較得出，腐蝕后(hou)期，在NaHSO3溶(rong)液中的(de)銹(xiu)層(ceng)保(bao)護(hu)性高于在其他兩種(zhong)介質(zhi)中的(de)，當除(chu)冰鹽溶(rong)液中加入NaHSO3溶(rong)液后(hou)，銹(xiu)層(ceng)保(bao)護(hu)性略好于除(chu)冰鹽中的(de)。

2.3 宏觀腐蝕(shi)形貌

圖(tu)4為(wei)帶氧(yang)化(hua)皮(pi)試樣(yang)在(zai)3種溶(rong)(rong)液(ye)(ye)(ye)中(zhong)腐(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)不(bu)同時(shi)(shi)間(jian)(jian)的(de)(de)(de)宏(hong)觀形貌圖(tu)。腐(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)初期（24 h），在(zai)除冰鹽(yan)和混(hun)合介質中(zhong)基本未腐(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)，而(er)在(zai)NaHSO3溶(rong)(rong)液(ye)(ye)(ye)中(zhong)已(yi)發生局(ju)(ju)(ju)(ju)部腐(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)。隨著腐(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)時(shi)(shi)間(jian)(jian)進行至192 h，各組試樣(yang)腐(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)加劇，在(zai)除冰鹽(yan)介質中(zhong)發生明(ming)顯的(de)(de)(de)局(ju)(ju)(ju)(ju)部腐(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)，局(ju)(ju)(ju)(ju)部氧(yang)化(hua)皮(pi)被破(po)壞出現(xian)(xian)點(dian)蝕(shi)(shi)(shi)(shi)(shi)坑，混(hun)合溶(rong)(rong)液(ye)(ye)(ye)中(zhong)既有局(ju)(ju)(ju)(ju)部點(dian)蝕(shi)(shi)(shi)(shi)(shi)坑，又伴隨全面腐(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)，這是因為(wei)腐(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)性離子侵入(ru)氧(yang)化(hua)皮(pi)的(de)(de)(de)缺(que)陷處，使(shi)得氧(yang)化(hua)皮(pi)-基體(ti)之間(jian)(jian)形成電偶電池(chi)[24]，加速基體(ti)腐(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)，但(dan)仍然有裸露氧(yang)化(hua)皮(pi)未被腐(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)；NaHSO3溶(rong)(rong)液(ye)(ye)(ye)中(zhong)表(biao)現(xian)(xian)為(wei)全面腐(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)，銹(xiu)層(ceng)(ceng)覆(fu)蓋(gai)不(bu)均(jun)(jun)勻(yun)，邊部出現(xian)(xian)橙紅色(se)的(de)(de)(de)銹(xiu)層(ceng)(ceng)。腐(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)中(zhong)期（288 h），除冰鹽(yan)溶(rong)(rong)液(ye)(ye)(ye)中(zhong)點(dian)蝕(shi)(shi)(shi)(shi)(shi)坑增多，NaHSO3溶(rong)(rong)液(ye)(ye)(ye)中(zhong)銹(xiu)層(ceng)(ceng)覆(fu)蓋(gai)逐漸(jian)均(jun)(jun)勻(yun)，混(hun)合溶(rong)(rong)液(ye)(ye)(ye)中(zhong)的(de)(de)(de)局(ju)(ju)(ju)(ju)部腐(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)逐漸(jian)轉化(hua)為(wei)全面腐(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)。腐(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)后(hou)期（480 h），帶氧(yang)化(hua)皮(pi)試樣(yang)在(zai)NaHSO3溶(rong)(rong)液(ye)(ye)(ye)中(zhong)被銹(xiu)層(ceng)(ceng)均(jun)(jun)勻(yun)覆(fu)蓋(gai)，表(biao)面局(ju)(ju)(ju)(ju)部出現(xian)(xian)鼓(gu)泡(pao)(pao)現(xian)(xian)象，這說明(ming)銹(xiu)層(ceng)(ceng)內應力(li)集中(zhong)于該(gai)區(qu)域，銹(xiu)層(ceng)(ceng)的(de)(de)(de)斷裂強(qiang)度已(yi)不(bu)能(neng)承受內應力(li)致使(shi)小部分(fen)鼓(gu)泡(pao)(pao)脫(tuo)落(luo)，脫(tuo)落(luo)的(de)(de)(de)地方呈(cheng)現(xian)(xian)紅褐色(se)。但(dan)是，在(zai)除冰鹽(yan)溶(rong)(rong)液(ye)(ye)(ye)中(zhong)仍然表(biao)現(xian)(xian)為(wei)局(ju)(ju)(ju)(ju)部腐(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)，說明(ming)氧(yang)化(hua)皮(pi)的(de)(de)(de)致密處難以(yi)形成電偶電池(chi)；在(zai)混(hun)合溶(rong)(rong)液(ye)(ye)(ye)中(zhong)，銹(xiu)層(ceng)(ceng)結合了兩(liang)種單相(xiang)介質中(zhong)的(de)(de)(de)銹(xiu)層(ceng)(ceng)顏色(se)呈(cheng)現(xian)(xian)黑(hei)褐色(se)，銹(xiu)層(ceng)(ceng)凹凸不(bu)平，疏松(song)易脫(tuo)落(luo)。

圖4   帶氧化皮Q345q鋼在3種溶(rong)液中(zhong)腐蝕不同時(shi)間(jian)的宏(hong)觀形(xing)貌(mao)

綜上所(suo)述，在(zai)除冰鹽(yan)溶液(ye)和混(hun)合(he)溶液(ye)中(zhong)(zhong)腐(fu)蝕(shi)(shi)(shi)192 h出現點蝕(shi)(shi)(shi)坑，腐(fu)蝕(shi)(shi)(shi)逐(zhu)漸(jian)加劇，符合(he)動力學曲線得到的(de)規律，整個過程中(zhong)(zhong)除冰鹽(yan)溶液(ye)中(zhong)(zhong)發(fa)生以(yi)點蝕(shi)(shi)(shi)為(wei)主的(de)局部腐(fu)蝕(shi)(shi)(shi)，混(hun)合(he)溶液(ye)中(zhong)(zhong)發(fa)生點蝕(shi)(shi)(shi)+全面腐(fu)蝕(shi)(shi)(shi)，而NaHSO3溶液(ye)中(zhong)(zhong)以(yi)全面腐(fu)蝕(shi)(shi)(shi)為(wei)主。

2.4 表面微觀形(xing)貌(mao)分析

2.4.1 帶氧(yang)化皮原始(shi)樣(yang)表面及截面形貌

圖5是帶(dai)氧(yang)化皮原始(shi)樣的(de)微(wei)觀形貌和(he)截面(mian)形貌。由(you)圖可知(zhi)，氧(yang)化皮形貌呈(cheng)多孔狀，而(er)且多孔狀結(jie)構不完(wan)整(zheng)；截面(mian)形貌來看，氧(yang)化皮厚度不均勻，內部存在橫向裂紋。

圖5   帶氧化皮(pi)Q345q鋼的表面形(xing)貌和(he)截面形(xing)貌

2.4.2 帶氧化皮試(shi)樣在不同(tong)介質中的微(wei)觀腐蝕形貌(mao)

圖(tu)(tu)6給出了帶氧化(hua)皮試樣在(zai)(zai)(zai)(zai)3種介質中(zhong)(zhong)腐蝕(shi)(shi)(shi)(shi)(shi)不(bu)同時間(jian)的(de)(de)(de)微觀(guan)形(xing)貌。由(you)圖(tu)(tu)可見(jian)，腐蝕(shi)(shi)(shi)(shi)(shi)初期(qi)（24 h），除冰鹽(yan)和(he)混合介質中(zhong)(zhong)氧化(hua)皮表面(mian)(mian)粗糙，局部存在(zai)(zai)(zai)(zai)鼓泡，且含有(you)細小裂紋；NaHSO3介質中(zhong)(zhong)的(de)(de)(de)銹(xiu)(xiu)層表面(mian)(mian)存在(zai)(zai)(zai)(zai)較大(da)(da)鼓泡且發(fa)(fa)生(sheng)(sheng)(sheng)破(po)(po)裂，表面(mian)(mian)覆蓋少(shao)量“花(hua)狀(zhuang)”或“針葉狀(zhuang)”的(de)(de)(de)腐蝕(shi)(shi)(shi)(shi)(shi)產(chan)物(wu)(wu)γ-FeOOH[25,26]，銹(xiu)(xiu)層中(zhong)(zhong)存在(zai)(zai)(zai)(zai)裂紋。腐蝕(shi)(shi)(shi)(shi)(shi)進行至192 h，在(zai)(zai)(zai)(zai)除冰鹽(yan)和(he)除冰鹽(yan)+NaHSO3介質中(zhong)(zhong)，鼓泡局部發(fa)(fa)生(sheng)(sheng)(sheng)破(po)(po)裂并出現點(dian)(dian)(dian)蝕(shi)(shi)(shi)(shi)(shi)坑(keng)(keng)，但是(shi)混合介質中(zhong)(zhong)的(de)(de)(de)點(dian)(dian)(dian)蝕(shi)(shi)(shi)(shi)(shi)坑(keng)(keng)區域(yu)較大(da)(da)，這(zhe)(zhe)是(shi)因為發(fa)(fa)生(sheng)(sheng)(sheng)點(dian)(dian)(dian)蝕(shi)(shi)(shi)(shi)(shi)的(de)(de)(de)同時伴隨全(quan)面(mian)(mian)腐蝕(shi)(shi)(shi)(shi)(shi)，在(zai)(zai)(zai)(zai)點(dian)(dian)(dian)蝕(shi)(shi)(shi)(shi)(shi)坑(keng)(keng)局部放大(da)(da)圖(tu)(tu)（圖(tu)(tu)6b和(he)圖(tu)(tu)6h右上(shang)圖(tu)(tu)）上(shang)可看到“團簇(cu)狀(zhuang)”的(de)(de)(de)腐蝕(shi)(shi)(shi)(shi)(shi)產(chan)物(wu)(wu)，此腐蝕(shi)(shi)(shi)(shi)(shi)產(chan)物(wu)(wu)為β-FeOOH[26]，由(you)氯(lv)化(hua)物(wu)(wu)轉化(hua)而來且穩定性最低(di)；在(zai)(zai)(zai)(zai)NaHSO3介質中(zhong)(zhong)，“花(hua)狀(zhuang)”腐蝕(shi)(shi)(shi)(shi)(shi)產(chan)物(wu)(wu)逐漸增多(duo)(duo)，大(da)(da)量鼓泡破(po)(po)裂致(zhi)使銹(xiu)(xiu)層表面(mian)(mian)凹(ao)凸(tu)不(bu)平產(chan)生(sheng)(sheng)(sheng)較大(da)(da)裂紋，這(zhe)(zhe)是(shi)由(you)鼓泡的(de)(de)(de)內應力(li)大(da)(da)于氧化(hua)皮的(de)(de)(de)強度引起(qi)的(de)(de)(de)，局部銹(xiu)(xiu)層顯得疏松多(duo)(duo)孔。腐蝕(shi)(shi)(shi)(shi)(shi)中(zhong)(zhong)期(qi)（288 h），除冰鹽(yan)介質中(zhong)(zhong)的(de)(de)(de)點(dian)(dian)(dian)蝕(shi)(shi)(shi)(shi)(shi)坑(keng)(keng)發(fa)(fa)生(sheng)(sheng)(sheng)擴展(zhan)，仍有(you)未被破(po)(po)壞的(de)(de)(de)氧化(hua)皮；NaHSO3介質中(zhong)(zhong)的(de)(de)(de)“花(hua)狀(zhuang)”腐蝕(shi)(shi)(shi)(shi)(shi)產(chan)物(wu)(wu)逐漸長大(da)(da)形(xing)成(cheng)“枝狀(zhuang)”，同時分布少(shao)量的(de)(de)(de)顆(ke)粒狀(zhuang)腐蝕(shi)(shi)(shi)(shi)(shi)產(chan)物(wu)(wu)α-FeOOH [25,27]；混合介質中(zhong)(zhong)的(de)(de)(de)“團簇(cu)狀(zhuang)”腐蝕(shi)(shi)(shi)(shi)(shi)產(chan)物(wu)(wu)形(xing)核長大(da)(da)，點(dian)(dian)(dian)蝕(shi)(shi)(shi)(shi)(shi)的(de)(de)(de)作用已將點(dian)(dian)(dian)蝕(shi)(shi)(shi)(shi)(shi)坑(keng)(keng)周圍的(de)(de)(de)氧化(hua)皮拱起(qi)。

圖6   帶氧化皮(pi)Q345q鋼在(zai)3種溶液中腐蝕不同時間的微觀形貌

腐蝕480 h的(de)銹(xiu)(xiu)層(ceng)(ceng)形貌(mao)如圖7所(suo)示。除冰鹽溶(rong)(rong)液中，“團絮(xu)狀”的(de)腐蝕產物(wu)在(zai)(zai)氧化(hua)(hua)皮(pi)脫(tuo)落的(de)地方(fang)聚(ju)集長大，并(bing)與氧化(hua)(hua)皮(pi)結(jie)合在(zai)(zai)一起，但與基(ji)體(ti)的(de)黏著性不強，氧化(hua)(hua)皮(pi)和(he)銹(xiu)(xiu)層(ceng)(ceng)均易(yi)(yi)脫(tuo)落；在(zai)(zai)NaHSO3溶(rong)(rong)液中，“針狀”腐蝕產物(wu)轉(zhuan)化(hua)(hua)為(wei)細(xi)小顆粒狀的(de)腐蝕產物(wu)，銹(xiu)(xiu)層(ceng)(ceng)結(jie)構得到(dao)改善(shan)且致密性增加(jia)；在(zai)(zai)除冰鹽+NaHSO3溶(rong)(rong)液中，“團絮(xu)狀”銹(xiu)(xiu)層(ceng)(ceng)擴展分布(bu)，疏松易(yi)(yi)脫(tuo)落。因此(ci)，在(zai)(zai)NaHSO3溶(rong)(rong)液中以全面腐蝕形成的(de)銹(xiu)(xiu)層(ceng)(ceng)顆粒具有一定的(de)保護性。

圖7   帶氧化皮Q345q鋼在3種溶液中腐蝕480 h的微觀形貌

2.4.3 銹(xiu)層(ceng)截面(mian)形貌(mao)分析

圖(tu)(tu)8是帶氧(yang)化(hua)(hua)(hua)皮(pi)(pi)鋼(gang)樣在(zai)(zai)3種溶(rong)(rong)(rong)液(ye)中(zhong)(zhong)(zhong)(zhong)腐(fu)(fu)蝕(shi)(shi)(shi)(shi)不同時間(jian)的(de)(de)截面(mian)(mian)形貌。從全貌來看，隨著(zhu)腐(fu)(fu)蝕(shi)(shi)(shi)(shi)時間(jian)的(de)(de)延長，銹(xiu)(xiu)層(ceng)(ceng)厚度有所(suo)增加(jia)。腐(fu)(fu)蝕(shi)(shi)(shi)(shi)初期(qi)（24 h），在(zai)(zai)除(chu)(chu)冰(bing)(bing)鹽和混(hun)(hun)合(he)溶(rong)(rong)(rong)液(ye)中(zhong)(zhong)(zhong)(zhong)，氧(yang)化(hua)(hua)(hua)皮(pi)(pi)表(biao)(biao)面(mian)(mian)基(ji)本(ben)未發(fa)生(sheng)腐(fu)(fu)蝕(shi)(shi)(shi)(shi)，內層(ceng)(ceng)比(bi)外(wai)層(ceng)(ceng)致密；而在(zai)(zai)NaHSO3溶(rong)(rong)(rong)液(ye)中(zhong)(zhong)(zhong)(zhong)氧(yang)化(hua)(hua)(hua)皮(pi)(pi)表(biao)(biao)面(mian)(mian)覆(fu)蓋(gai)一(yi)層(ceng)(ceng)不均(jun)勻的(de)(de)銹(xiu)(xiu)層(ceng)(ceng)。隨著(zhu)腐(fu)(fu)蝕(shi)(shi)(shi)(shi)進行至192 h，除(chu)(chu)冰(bing)(bing)鹽和混(hun)(hun)合(he)溶(rong)(rong)(rong)液(ye)中(zhong)(zhong)(zhong)(zhong)出現較深(shen)(shen)的(de)(de)裂紋，氧(yang)化(hua)(hua)(hua)皮(pi)(pi)變得粗糙(cao)，在(zai)(zai)局部放大(da)圖(tu)(tu)上（圖(tu)(tu)9a和9c）看到(dao)局部銹(xiu)(xiu)層(ceng)(ceng)較深(shen)(shen)，甚至穿透氧(yang)化(hua)(hua)(hua)皮(pi)(pi)腐(fu)(fu)蝕(shi)(shi)(shi)(shi)到(dao)鋼(gang)基(ji)體，這(zhe)是因為在(zai)(zai)該(gai)部位(wei)發(fa)生(sheng)了明顯的(de)(de)點蝕(shi)(shi)(shi)(shi)，使得局部銹(xiu)(xiu)層(ceng)(ceng)深(shen)(shen)度較大(da)，對比(bi)發(fa)現混(hun)(hun)合(he)溶(rong)(rong)(rong)液(ye)中(zhong)(zhong)(zhong)(zhong)的(de)(de)點蝕(shi)(shi)(shi)(shi)深(shen)(shen)度更明顯（圖(tu)(tu)9c）；在(zai)(zai)NaHSO3溶(rong)(rong)(rong)液(ye)中(zhong)(zhong)(zhong)(zhong)銹(xiu)(xiu)層(ceng)(ceng)逐漸(jian)覆(fu)蓋(gai)氧(yang)化(hua)(hua)(hua)皮(pi)(pi)表(biao)(biao)面(mian)(mian)，氧(yang)化(hua)(hua)(hua)皮(pi)(pi)變得疏松(song)(song)不平整(zheng)。腐(fu)(fu)蝕(shi)(shi)(shi)(shi)中(zhong)(zhong)(zhong)(zhong)期(qi)（288 h），除(chu)(chu)冰(bing)(bing)鹽溶(rong)(rong)(rong)液(ye)中(zhong)(zhong)(zhong)(zhong)的(de)(de)點蝕(shi)(shi)(shi)(shi)區域(yu)增大(da)，在(zai)(zai)圖(tu)(tu)9b所(suo)示的(de)(de)局部放大(da)圖(tu)(tu)上看到(dao)鋼(gang)基(ji)體處形成一(yi)層(ceng)(ceng)疏松(song)(song)的(de)(de)內銹(xiu)(xiu)層(ceng)(ceng)，同時部分銹(xiu)(xiu)層(ceng)(ceng)深(shen)(shen)入到(dao)未破壞(huai)的(de)(de)氧(yang)化(hua)(hua)(hua)皮(pi)(pi)中(zhong)(zhong)(zhong)(zhong)間(jian)，產(chan)生(sheng)的(de)(de)內應力將氧(yang)化(hua)(hua)(hua)皮(pi)(pi)隆起(qi)；在(zai)(zai)NaHSO3溶(rong)(rong)(rong)液(ye)中(zhong)(zhong)(zhong)(zhong)，銹(xiu)(xiu)層(ceng)(ceng)幾乎(hu)覆(fu)蓋(gai)了整(zheng)個氧(yang)化(hua)(hua)(hua)皮(pi)(pi)表(biao)(biao)面(mian)(mian)，并與基(ji)體緊(jin)密結合(he)；在(zai)(zai)除(chu)(chu)冰(bing)(bing)鹽+NaHSO3溶(rong)(rong)(rong)液(ye)中(zhong)(zhong)(zhong)(zhong)，點蝕(shi)(shi)(shi)(shi)部位(wei)腐(fu)(fu)蝕(shi)(shi)(shi)(shi)深(shen)(shen)度到(dao)達(da)鋼(gang)基(ji)體，同時伴隨著(zhu)全面(mian)(mian)腐(fu)(fu)蝕(shi)(shi)(shi)(shi)，在(zai)(zai)局部放大(da)圖(tu)(tu)上（圖(tu)(tu)9d）仍(reng)可(ke)以看到(dao)未破壞(huai)的(de)(de)氧(yang)化(hua)(hua)(hua)皮(pi)(pi)。

圖8   帶(dai)氧化皮(pi)Q345q鋼在3種(zhong)溶液中腐蝕不同(tong)時間的截面(mian)形貌

圖9   帶氧(yang)化皮Q345q鋼在除冰(bing)鹽和(he)混(hun)合(he)溶(rong)液中腐(fu)蝕不同時間(jian)的截面局部放(fang)大形貌

在(zai)3種介(jie)質中(zhong)(zhong)腐蝕480 h的(de)截(jie)面形貌如圖10所(suo)示，除(chu)冰鹽(yan)介(jie)質中(zhong)(zhong)由于Cl-的(de)點(dian)蝕作用，致使銹(xiu)層(ceng)疏松多(duo)孔，與基體(ti)的(de)粘(zhan)著力差；NaHSO3溶液中(zhong)(zhong)的(de)銹(xiu)層(ceng)逐漸變(bian)得致密(mi)，與基體(ti)緊密(mi)結合(he)；而在(zai)除(chu)冰鹽(yan)+NaHSO3介(jie)質中(zhong)(zhong)，雖然銹(xiu)層(ceng)較厚，但是內部存(cun)在(zai)橫(heng)向裂紋(wen)和不(bu)完整的(de)氧(yang)化皮，與基體(ti)結合(he)處的(de)內銹(xiu)層(ceng)致密(mi)性(xing)得到改善。

2.5 電(dian)化(hua)學(xue)分析(xi)

圖(tu)11是帶氧化(hua)(hua)皮鋼(gang)在三種溶(rong)(rong)(rong)液中腐蝕不(bu)同時間(jian)后的極(ji)(ji)化(hua)(hua)曲線(xian)，其相(xiang)應的電(dian)化(hua)(hua)學(xue)(xue)參數如表(biao)4所示。由(you)圖(tu)11可知，無論帶氧化(hua)(hua)皮鋼(gang)樣表(biao)面是否有銹，其腐蝕過(guo)(guo)程(cheng)同時受陽極(ji)(ji)和(he)(he)陰(yin)極(ji)(ji)反應控(kong)(kong)制，陰(yin)極(ji)(ji)過(guo)(guo)程(cheng)表(biao)現為氧溶(rong)(rong)(rong)解極(ji)(ji)限擴散(san)控(kong)(kong)制和(he)(he)腐蝕產物還(huan)原的電(dian)化(hua)(hua)學(xue)(xue)控(kong)(kong)制[28]。但是隨著腐蝕時間(jian)的延長(chang)，氧極(ji)(ji)限擴散(san)控(kong)(kong)制逐漸(jian)變為電(dian)化(hua)(hua)學(xue)(xue)活(huo)化(hua)(hua)控(kong)(kong)制，而陽極(ji)(ji)過(guo)(guo)程(cheng)主要是電(dian)荷(he)轉移控(kong)(kong)制的電(dian)化(hua)(hua)學(xue)(xue)溶(rong)(rong)(rong)解。

圖11   帶氧化皮(pi)Q345q鋼在三種(zhong)溶液中腐蝕不同(tong)時(shi)間(jian)后的極(ji)化曲線(xian)

圖11a顯示，在除冰鹽介質中自(zi)腐(fu)(fu)(fu)蝕(shi)電位(wei)隨時間的(de)延(yan)長先(xian)減(jian)小(xiao)(xiao)(xiao)（24~144 h）后(hou)(hou)增(zeng)大(da)（144~480 h），說(shuo)明發生腐(fu)(fu)(fu)蝕(shi)的(de)傾向性先(xian)增(zeng)大(da)后(hou)(hou)減(jian)小(xiao)(xiao)(xiao)，主(zhu)要是因(yin)(yin)為鹽離子侵入氧化皮(pi)表面缺陷(xian)處加速了(le)(le)腐(fu)(fu)(fu)蝕(shi)，后(hou)(hou)期的(de)腐(fu)(fu)(fu)蝕(shi)過(guo)程(cheng)(cheng)中表面有腐(fu)(fu)(fu)蝕(shi)產物的(de)累積，在一定(ding)程(cheng)(cheng)度上減(jian)緩了(le)(le)腐(fu)(fu)(fu)蝕(shi)。24~144 h陰(yin)極(ji)(ji)電流密度減(jian)小(xiao)(xiao)(xiao)是因(yin)(yin)為在192 h之前帶(dai)氧化皮(pi)鋼(gang)腐(fu)(fu)(fu)蝕(shi)處于“潛伏期”（圖1），表面含有大(da)量未破壞的(de)氧化皮(pi)，同時還覆(fu)蓋(gai)少(shao)量的(de)銹(xiu)層和(he)大(da)量的(de)腐(fu)(fu)(fu)蝕(shi)薄(bo)膜，陰(yin)極(ji)(ji)過(guo)程(cheng)(cheng)受到了(le)(le)一定(ding)的(de)阻礙。在144~480 h腐(fu)(fu)(fu)蝕(shi)過(guo)程(cheng)(cheng)中，陽(yang)極(ji)(ji)電流密度增(zeng)大(da)，說(shuo)明小(xiao)(xiao)(xiao)陽(yang)極(ji)(ji)過(guo)程(cheng)(cheng)加快(kuai)；陰(yin)極(ji)(ji)電流密度也增(zeng)大(da)，其主(zhu)要原因(yin)(yin)是大(da)陰(yin)極(ji)(ji)發生腐(fu)(fu)(fu)蝕(shi)產物的(de)還原，同時腐(fu)(fu)(fu)蝕(shi)膜和(he)不穩定(ding)銹(xiu)層的(de)脫落，加快(kuai)了(le)(le)陰(yin)極(ji)(ji)過(guo)程(cheng)(cheng)。

觀察圖(tu)11b發(fa)現，在(zai)NaHSO3溶(rong)液中(zhong)，自腐蝕(shi)電(dian)位隨時(shi)間的(de)延(yan)(yan)長而明顯增(zeng)大(da)，表(biao)明銹(xiu)(xiu)層(ceng)(ceng)的(de)耐蝕(shi)性隨時(shi)間的(de)延(yan)(yan)長有所提高，腐蝕(shi)初期（24~72 h），陰極(ji)(ji)(ji)(ji)Tafel曲(qu)(qu)線的(de)斜(xie)率(lv)較大(da)，主(zhu)要(yao)以(yi)極(ji)(ji)(ji)(ji)限(xian)擴散為控(kong)制(zhi)步驟；在(zai)144~480 h的(de)腐蝕(shi)過(guo)程(cheng)中(zhong)氧極(ji)(ji)(ji)(ji)限(xian)擴散控(kong)制(zhi)逐(zhu)漸消失，陰極(ji)(ji)(ji)(ji)Tafel曲(qu)(qu)線的(de)斜(xie)率(lv)減小，陰極(ji)(ji)(ji)(ji)過(guo)程(cheng)主(zhu)要(yao)是(shi)以(yi)γ-FeOOH還原為主(zhu)的(de)電(dian)荷傳遞(di)控(kong)制(zhi)，陰極(ji)(ji)(ji)(ji)電(dian)流(liu)密(mi)度(du)增(zeng)大(da)，陰極(ji)(ji)(ji)(ji)過(guo)程(cheng)加速；在(zai)72~144 h發(fa)生(sheng)了(le)鈍化(hua)，是(shi)因(yin)(yin)為銹(xiu)(xiu)層(ceng)(ceng)在(zai)氧化(hua)皮表(biao)面覆蓋抑制(zhi)了(le)陽(yang)極(ji)(ji)(ji)(ji)溶(rong)解過(guo)程(cheng)；在(zai)144~480 h之間陽(yang)極(ji)(ji)(ji)(ji)電(dian)流(liu)密(mi)度(du)先(xian)增(zeng)大(da)后減小，其原因(yin)(yin)是(shi)氧化(hua)皮破壞程(cheng)度(du)增(zeng)大(da)，鈍化(hua)膜逐(zhu)漸遭到(dao)了(le)破壞，致使鋼基體(ti)發(fa)生(sheng)溶(rong)解，直到(dao)480 h生(sheng)成了(le)一層(ceng)(ceng)較厚(hou)的(de)銹(xiu)(xiu)層(ceng)(ceng)，陽(yang)極(ji)(ji)(ji)(ji)電(dian)流(liu)密(mi)度(du)降低。

從圖11c看到，在除冰鹽(yan)+NaHSO3溶(rong)液中(zhong)，帶(dai)銹(xiu)試樣的(de)自(zi)腐(fu)(fu)蝕(shi)電位(wei)的(de)變化與在除冰鹽(yan)中(zhong)的(de)一致(zhi)，但腐(fu)(fu)蝕(shi)時間對陰極腐(fu)(fu)蝕(shi)行為影響不大，而陽極電流密度(du)減小說明銹(xiu)層逐漸覆蓋，陽極過程受阻。

從表4給出的極化曲線參(can)數可知，除冰鹽介質(zhi)中銹(xiu)層的自(zi)腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)電(dian)(dian)(dian)流(liu)(liu)密度先(xian)減(jian)小(xiao)（24~144 h）后(hou)增(zeng)(zeng)大(da)（144~480 h），說明192 h前腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)增(zeng)(zeng)重幾(ji)乎(hu)不(bu)變，腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)速(su)(su)(su)(su)率(lv)(lv)減(jian)小(xiao)，隨著氧化皮的破壞和鋼(gang)基體的腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)，腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)速(su)(su)(su)(su)率(lv)(lv)逐漸增(zeng)(zeng)大(da)，與動力(li)學(xue)規律吻合(he)。在(zai)NaHSO3溶(rong)液中，自(zi)腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)電(dian)(dian)(dian)流(liu)(liu)密度在(zai)24~72 h減(jian)小(xiao)，說明腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)速(su)(su)(su)(su)率(lv)(lv)減(jian)小(xiao)；在(zai)72~288 h之間增(zeng)(zeng)大(da)，腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)速(su)(su)(su)(su)率(lv)(lv)增(zeng)(zeng)大(da)，這是因為氧化皮溶(rong)解過(guo)程加快；在(zai)480 h時又達到最小(xiao)值，腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)速(su)(su)(su)(su)率(lv)(lv)減(jian)小(xiao)，這是由基體被(bei)一層較厚的銹(xiu)層覆蓋所導致。在(zai)除冰鹽+ NaHSO3溶(rong)液中，自(zi)腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)電(dian)(dian)(dian)流(liu)(liu)密度先(xian)增(zeng)(zeng)大(da)后(hou)減(jian)小(xiao)，相(xiang)(xiang)比較于除冰鹽溶(rong)液，腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)速(su)(su)(su)(su)率(lv)(lv)在(zai)24~288 h增(zeng)(zeng)大(da)，隨著點蝕(shi)(shi)(shi)(shi)(shi)(shi)+全(quan)面腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)的同(tong)時進行，鋼(gang)表面被(bei)腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)產物覆蓋，腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)速(su)(su)(su)(su)率(lv)(lv)在(zai)480 h有所減(jian)小(xiao)。因此(ci)，根據帶氧化皮帶銹(xiu)鋼(gang)的自(zi)腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)電(dian)(dian)(dian)流(liu)(liu)密度的變化可以判斷腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)(shi)(shi)(shi)速(su)(su)(su)(su)率(lv)(lv)的變化，結果與動力(li)學(xue)曲線相(xiang)(xiang)吻合(he)。

本(ben)實驗所用的(de)(de)Q345q鋼，采(cai)用控(kong)軋控(kong)冷(leng)(leng)技術（TMCP），其表面形成了(le)Fe2O3、Fe3O4兩層結構的(de)(de)氧(yang)(yang)化(hua)(hua)(hua)(hua)(hua)皮，在軋制和(he)控(kong)制冷(leng)(leng)卻速度(du)的(de)(de)過程(cheng)中(zhong)往(wang)往(wang)會(hui)產生缺陷(xian)，氧(yang)(yang)化(hua)(hua)(hua)(hua)(hua)皮在腐(fu)(fu)蝕環(huan)境(jing)中(zhong)不(bu)穩定，在缺陷(xian)處優(you)先發生局(ju)部腐(fu)(fu)蝕，氧(yang)(yang)化(hua)(hua)(hua)(hua)(hua)皮的(de)(de)致密處雖然在腐(fu)(fu)蝕初期有阻礙作用，但隨著腐(fu)(fu)蝕的(de)(de)進行氧(yang)(yang)化(hua)(hua)(hua)(hua)(hua)皮會(hui)逐漸轉化(hua)(hua)(hua)(hua)(hua)或溶解，轉化(hua)(hua)(hua)(hua)(hua)不(bu)完整的(de)(de)氧(yang)(yang)化(hua)(hua)(hua)(hua)(hua)皮將會(hui)破(po)(po)壞(huai)銹(xiu)層的(de)(de)穩定性。在不(bu)同的(de)(de)腐(fu)(fu)蝕環(huan)境(jing)下，氧(yang)(yang)化(hua)(hua)(hua)(hua)(hua)皮的(de)(de)腐(fu)(fu)蝕行為亦(yi)不(bu)同。因此，研究(jiu)氧(yang)(yang)化(hua)(hua)(hua)(hua)(hua)皮在不(bu)同環(huan)境(jing)下的(de)(de)破(po)(po)壞(huai)機(ji)理(li)和(he)腐(fu)(fu)蝕機(ji)理(li)很有必要(yao)。

銹層中Fe2+繼續與γ-FeOOH反應(ying)生成Fe3O4，這樣(yang)生成的(de)(de)Fe3O4補償了溶解的(de)(de)氧化(hua)皮，在(zai)(zai)腐(fu)蝕初期和中期Fe3O4的(de)(de)峰強很少變化(hua)。當γ-FeOOH大部分轉化(hua)為α-FeOOH時，γ-FeOOH不足以補償Fe3O4的(de)(de)生成，使得在(zai)(zai)腐(fu)蝕后(hou)期Fe2O3和Fe3O4的(de)(de)含量(liang)降低，α-FeOOH含量(liang)增多，銹層的(de)(de)保護性有(you)所增強。

在(zai)除冰(bing)鹽+NaHSO3溶(rong)(rong)液中(zhong)(zhong)，NaHSO3溶(rong)(rong)液的(de)(de)加入(ru)使(shi)溶(rong)(rong)液的(de)(de)pH顯(xian)酸性，氧(yang)化(hua)皮表面的(de)(de)Fe（OH）2、Fe（OH）3、Ca（OH）2、Fes[Fe（OH）2]被H+溶(rong)(rong)解生(sheng)(sheng)成相(xiang)應(ying)(ying)的(de)(de)陽離(li)子(zi)，大(da)量的(de)(de)陽離(li)子(zi)聚(ju)集在(zai)一(yi)起增(zeng)大(da)了溶(rong)(rong)液的(de)(de)導電(dian)性，陽離(li)子(zi)移動的(de)(de)范圍增(zeng)大(da)，不但發生(sheng)(sheng)Cl-為主的(de)(de)點蝕(shi)(shi)(shi)作用，而且(qie)還有大(da)面積的(de)(de)全面腐(fu)(fu)蝕(shi)(shi)(shi)，故腐(fu)(fu)蝕(shi)(shi)(shi)速(su)率比除冰(bing)鹽單一(yi)介(jie)(jie)質(zhi)的(de)(de)大(da)，說(shuo)明(ming)Cl-與HSO3-存在(zai)協同效應(ying)(ying)，加速(su)了氧(yang)化(hua)皮的(de)(de)破(po)壞(huai)和(he)溶(rong)(rong)解。但是，Cl-的(de)(de)自(zi)催化(hua)效應(ying)(ying)沒有完全消除，在(zai)整(zheng)個腐(fu)(fu)蝕(shi)(shi)(shi)過程中(zhong)(zhong)產(chan)生(sheng)(sheng)中(zhong)(zhong)間腐(fu)(fu)蝕(shi)(shi)(shi)產(chan)物HFeCl4（H2O）6和(he)β-FeOOH。研(yan)究表明(ming)[35]，呈酸性的(de)(de)介(jie)(jie)質(zhi)有利(li)于β-FeOOH轉化(hua)為α-FeOOH和(he)Fe3O4，因(yin)此腐(fu)(fu)蝕(shi)(shi)(shi)后期生(sheng)(sheng)成的(de)(de)α-FeOOH是由兩部分構成，加上氯化(hua)物和(he)不穩定的(de)(de)β-FeOOH使(shi)銹層(ceng)變得(de)疏松，其銹層(ceng)保護性介(jie)(jie)于在(zai)兩種單相(xiang)介(jie)(jie)質(zhi)中(zhong)(zhong)的(de)(de)。

4 結論

（1） 帶氧化(hua)皮Q345q鋼在(zai)三種(zhong)模(mo)擬西北典型大(da)(da)氣環境中(zhong)的腐(fu)蝕(shi)速率(lv)大(da)(da)小順(shun)序為(wei)：NaHSO3>除(chu)冰鹽(yan)(yan)+NaHSO3>除(chu)冰鹽(yan)(yan)。在(zai)432 h后，在(zai)NaHSO3和(he)混合(he)介質(zhi)中(zhong)速率(lv)增大(da)(da)逐(zhu)漸(jian)減緩(huan)。但是，在(zai)192 h以下，除(chu)冰鹽(yan)(yan)和(he)混合(he)介質(zhi)的n<1，說(shuo)明氧化(hua)皮對(dui)基體具(ju)有(you)一(yi)定(ding)的保(bao)護(hu)作用，除(chu)冰鹽(yan)(yan)介質(zhi)中(zhong)主(zhu)要以“大(da)(da)陰極(ji)小陽極(ji)”的點蝕(shi)為(wei)主(zhu)，混合(he)介質(zhi)中(zhong)以點蝕(shi)和(he)全(quan)面腐(fu)蝕(shi)為(wei)主(zhu)。當腐(fu)蝕(shi)時間(jian)大(da)(da)于192 h，除(chu)冰鹽(yan)(yan)和(he)混合(he)介質(zhi)的n>1，說(shuo)明氧化(hua)皮逐(zhu)漸(jian)遭到破(po)壞，銹層不具(ju)保(bao)護(hu)性(xing)。而在(zai)NaHSO3介質(zhi)中(zhong)，從(cong)整體來看主(zhu)要以全(quan)面腐(fu)蝕(shi)為(wei)主(zhu)，92 h后雖然(ran)n值大(da)(da)于1，但小于其(qi)它兩種(zhong)介質(zhi)中(zhong)的，其(qi)銹層保(bao)護(hu)性(xing)較強(qiang)。

（2） 在除冰鹽和除冰鹽+NaHSO3溶(rong)液中(zhong)，腐蝕產(chan)物(wu)主(zhu)要是β-FeOOH、γ-FeOOH、HFeCl4（H2O）6、Fe2O3、Fe3O4以及少量的(de)(de)α-FeOOH，NaHSO3溶(rong)液中(zhong)的(de)(de)腐蝕產(chan)物(wu)主(zhu)要是α-FeOOH、γ-FeOOH、Fe2O3、Fe3O4。Cl-與HSO3-的(de)(de)協同(tong)作用加速了氧化(hua)(hua)皮的(de)(de)溶(rong)解(jie)和破壞，不穩定的(de)(de)β-FeOOH和氯化(hua)(hua)物(wu)致使(shi)銹(xiu)層致密性下降。

（3） 氧化(hua)(hua)皮/銹(xiu)層(ceng)(ceng)的(de)自腐(fu)(fu)蝕(shi)電(dian)流(liu)(liu)密(mi)度的(de)變化(hua)(hua)反應腐(fu)(fu)蝕(shi)速率的(de)變化(hua)(hua)。除冰(bing)鹽(yan)溶液(ye)的(de)銹(xiu)層(ceng)(ceng)腐(fu)(fu)蝕(shi)電(dian)流(liu)(liu)密(mi)度先減小(xiao)（24~144 h）后增大(da)（144~288 h）；NaHSO3溶液(ye)的(de)銹(xiu)層(ceng)(ceng)腐(fu)(fu)蝕(shi)電(dian)流(liu)(liu)密(mi)度在72 h后增大(da)，480 h時達到最小(xiao)值(zhi)；除冰(bing)鹽(yan)+NaHSO3溶液(ye)的(de)銹(xiu)層(ceng)(ceng)腐(fu)(fu)蝕(shi)電(dian)流(liu)(liu)密(mi)度先增大(da)（24~288 h），480 h時有所減小(xiao)。