腐蝕檢測是運行中設備防腐的重要組成部分,可以分為兩大類:一是在實際環境中,通過追蹤金屬表面的腐蝕行為而獲得設備腐蝕過程的相關信息,稱作腐蝕的在線監測,簡稱監測。二是在設備運行一段時間后,檢測設備的部件零件的情況而獲得的腐蝕結果,稱作腐蝕的離線檢測,簡稱檢測。今天在這里我們要特別介紹一下腐蝕的在線監測。
1. 腐蝕掛片失重法
把已知重量的(de)(de)金屬試(shi)樣放入腐蝕(shi)系統中,經過一定時(shi)間的(de)(de)暴露,取出(chu)樣品進行清(qing)洗(xi)、稱(cheng)重,根據其質(zhi)量變化(hua)測算出(chu)平均腐蝕(shi)速率。
2. 在線電阻探針法(fa)
常被(bei)稱為(wei)(wei)可自動測(ce)(ce)量(liang)的掛片失重法。既能(neng)(neng)在(zai)液相(xiang)(電(dian)(dian)(dian)解(jie)質(zhi)或非電(dian)(dian)(dian)解(jie)質(zhi))中(zhong)測(ce)(ce)定,也能(neng)(neng)在(zai)氣相(xiang)中(zhong)測(ce)(ce)定。電(dian)(dian)(dian)阻探(tan)針法所測(ce)(ce)量(liang)的是金屬元(yuan)件的電(dian)(dian)(dian)阻因為(wei)(wei)橫截(jie)面(mian)積(ji)因腐蝕(shi)(shi)減少所造成的。電(dian)(dian)(dian)阻探(tan)針分(fen)為(wei)(wei),暴露在(zai)腐蝕(shi)(shi)介質(zhi)中(zhong)的測(ce)(ce)量(liang)元(yuan)件和不與腐蝕(shi)(shi)介質(zhi)接觸的參考元(yuan)件兩部分(fen)。
3. 電化學法
因(yin)為(wei)腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)本身就歸結為(wei)電(dian)(dian)(dian)(dian)化(hua)(hua)(hua)(hua)學(xue)(xue)反應(ying)(ying)的(de)過(guo)程,所以在眾多的(de)腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)監測(ce)系統(tong)中(zhong),電(dian)(dian)(dian)(dian)化(hua)(hua)(hua)(hua)學(xue)(xue)測(ce)試技術應(ying)(ying)用(yong)的(de)最(zui)為(wei)廣泛(fan)。它的(de)優點在于(yu),可(ke)進(jin)行(xing)瞬時(shi)(shi)腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)速度的(de)測(ce)量,反應(ying)(ying)靈(ling)敏,適于(yu)電(dian)(dian)(dian)(dian)解質(zhi)介質(zhi)。而(er)在電(dian)(dian)(dian)(dian)化(hua)(hua)(hua)(hua)學(xue)(xue)監測(ce)方法(fa)(fa)中(zhong)又細分為(wei)有:電(dian)(dian)(dian)(dian)位法(fa)(fa)、線性極(ji)(ji)化(hua)(hua)(hua)(hua)法(fa)(fa)和極(ji)(ji)化(hua)(hua)(hua)(hua)電(dian)(dian)(dian)(dian)阻法(fa)(fa)等。其(qi)中(zhong)極(ji)(ji)化(hua)(hua)(hua)(hua)電(dian)(dian)(dian)(dian)阻(LPR)法(fa)(fa),是(shi)指(zhi)利用(yong)金(jin)屬材(cai)料在腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)介質(zhi)中(zhong)發(fa)生的(de)電(dian)(dian)(dian)(dian)化(hua)(hua)(hua)(hua)學(xue)(xue)極(ji)(ji)化(hua)(hua)(hua)(hua)行(xing)為(wei),將電(dian)(dian)(dian)(dian)化(hua)(hua)(hua)(hua)學(xue)(xue)探頭(三(san)電(dian)(dian)(dian)(dian)極(ji)(ji)組裝)安裝在腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)環(huan)境中(zhong),然后(hou)進(jin)行(xing)電(dian)(dian)(dian)(dian)化(hua)(hua)(hua)(hua)學(xue)(xue)極(ji)(ji)化(hua)(hua)(hua)(hua),測(ce)量其(qi)電(dian)(dian)(dian)(dian)化(hua)(hua)(hua)(hua)學(xue)(xue)響(xiang)應(ying)(ying),計(ji)算(suan)出(chu)當時(shi)(shi)的(de)極(ji)(ji)化(hua)(hua)(hua)(hua)電(dian)(dian)(dian)(dian)阻,再根(gen)據(ju)理論(lun)計(ji)算(suan)得到的(de)換算(suan)系數,計(ji)算(suan)腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)電(dian)(dian)(dian)(dian)流(即腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)速度)實現快速腐(fu)(fu)(fu)(fu)蝕(shi)(shi)(shi)速度監測(ce)。
4. 化學分析法
化(hua)學分(fen)析法(fa)(fa)并(bing)不是(shi)對(dui)腐蝕(shi)(shi)(shi)狀(zhuang)況(kuang)進行直接監測(ce)(ce)(ce),而是(shi)對(dui)影響腐蝕(shi)(shi)(shi)的(de)(de)各種(zhong)因素(su)及腐蝕(shi)(shi)(shi)產物進行追蹤,再用各種(zhong)數據處理方法(fa)(fa)來間(jian)接監測(ce)(ce)(ce)腐蝕(shi)(shi)(shi)狀(zhuang)況(kuang),并(bing)分(fen)析找出腐蝕(shi)(shi)(shi)規律,作出預測(ce)(ce)(ce)。滲氫(qing)(qing)(qing)(qing)(qing)檢測(ce)(ce)(ce)就是(shi)一(yi)種(zhong)典型的(de)(de)化(hua)學分(fen)析法(fa)(fa)。氫(qing)(qing)(qing)(qing)(qing)是(shi)去極化(hua)腐蝕(shi)(shi)(shi)的(de)(de)產物.在酸性(xing)介質中(zhong)(zhong),由(you)于鋼(gang)構件吸(xi)收(shou)(shou)了(le)氫(qing)(qing)(qing)(qing)(qing)原子(腐蝕(shi)(shi)(shi)產生的(de)(de))或(huo)在高溫下吸(xi)收(shou)(shou)了(le)原子氫(qing)(qing)(qing)(qing)(qing)(工藝介質中(zhong)(zhong)的(de)(de))從而產生氫(qing)(qing)(qing)(qing)(qing)脆、氫(qing)(qing)(qing)(qing)(qing)致開裂(lie)和氫(qing)(qing)(qing)(qing)(qing)鼓泡。通過(guo)對(dui)氫(qing)(qing)(qing)(qing)(qing)氣量的(de)(de)測(ce)(ce)(ce)定(ding)可測(ce)(ce)(ce)得金(jin)屬的(de)(de)腐蝕(shi)(shi)(shi)速度。氫(qing)(qing)(qing)(qing)(qing)氣量的(de)(de)測(ce)(ce)(ce)定(ding)通常用探(tan)氫(qing)(qing)(qing)(qing)(qing)針來完成。通過(guo)測(ce)(ce)(ce)量氫(qing)(qing)(qing)(qing)(qing)(吸(xi)收(shou)(shou)的(de)(de))經(jing)過(guo)1~2mm的(de)(de)鋼(gang)在狹窄(zhai)的(de)(de)環狀(zhuang)空(kong)間(jian)中(zhong)(zhong)的(de)(de)壓力(li)增(zeng)加速度,估算擴散到鋼(gang)中(zhong)(zhong)的(de)(de)氫(qing)(qing)(qing)(qing)(qing)氣量,進而估計(ji)鋼(gang)的(de)(de)腐蝕(shi)(shi)(shi)程度。
以(yi)上列(lie)舉的都是(shi)(shi)比較(jiao)常見和常用的腐蝕(shi)在(zai)線檢(jian)測方(fang)法(fa)(fa)。其它在(zai)線監測技術(shu),表(biao)面檢(jian)查法(fa)(fa)、腐蝕(shi)余量法(fa)(fa)等都是(shi)(shi)腐蝕(shi)監測最基本(ben)的方(fang)法(fa)(fa),這(zhe)些方(fang)法(fa)(fa)對技術(shu)的要求(qiu)不是(shi)(shi)很高,屬于經(jing)典的腐蝕(shi)研究方(fang)法(fa)(fa)。
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