一塊(kuai)金(jin)屬(shu)(shu)(shu)(shu)，表(biao)面看來(lai)挺光(guang)滑，可是在顯微鏡下就(jiu)會發現，它的結(jie)構很不(bu)均勻(yun)，這就(jiu)為“病從(cong)(cong)口(kou)(kou)入(ru)”大開(kai)了方(fang)便之門(men)，因為金(jin)屬(shu)(shu)(shu)(shu)遍(bian)體都是“口(kou)(kou)”，準(zhun)確一點說，不(bu)是病從(cong)(cong)口(kou)(kou)入(ru)，而是病從(cong)(cong)“皮(pi)”入(ru)了。所以金(jin)屬(shu)(shu)(shu)(shu)的常見病--腐蝕，一般都開(kai)始(shi)于(yu)“皮(pi)膚病”。首先是金(jin)屬(shu)(shu)(shu)(shu)“皮(pi)膚潰瘍”，然后逐漸侵入(ru)到(dao)內部。由于(yu)金(jin)屬(shu)(shu)(shu)(shu)接觸的物(wu)質多(duo)(duo)種(zhong)多(duo)(duo)樣，“得(de)病”的條件也(ye)各不(bu)相同，所以金(jin)屬(shu)(shu)(shu)(shu)的常見病還可以分(fen)為許多(duo)(duo)種(zhong)。也(ye)就(jiu)是說，金(jin)屬(shu)(shu)(shu)(shu)腐蝕可以分(fen)為許多(duo)(duo)種(zhong)類。

金(jin)(jin)屬(shu)腐(fu)(fu)蝕(shi)分類(lei)的(de)(de)(de)方法很多，常見(jian)的(de)(de)(de)一(yi)種就是(shi)根據腐(fu)(fu)蝕(shi)過程中是(shi)否有電(dian)流(liu)產生，分為化學(xue)腐(fu)(fu)蝕(shi)和(he)電(dian)化學(xue)腐(fu)(fu)蝕(shi)兩類(lei)。化學(xue)腐(fu)(fu)蝕(shi)一(yi)般是(shi)在(zai)干(gan)燥和(he)高(gao)溫的(de)(de)(de)環境下發(fa)生的(de)(de)(de)，它是(shi)金(jin)(jin)屬(shu)的(de)(de)(de)“干(gan)熱病”；電(dian)化學(xue)腐(fu)(fu)蝕(shi)是(shi)在(zai)潮(chao)濕(shi)的(de)(de)(de)環境下發(fa)生的(de)(de)(de)，它是(shi)金(jin)(jin)屬(shu)的(de)(de)(de)“風(feng)濕(shi)病”。

 化學(xue)(xue)(xue)腐蝕(shi)(shi)是金(jin)屬(shu)(shu)在(zai)不導電環境中的(de)腐蝕(shi)(shi)，它是金(jin)屬(shu)(shu)與某種物質直接接觸時(shi)發生(sheng)的(de)化學(xue)(xue)(xue)反(fan)應(ying)。在(zai)化學(xue)(xue)(xue)腐蝕(shi)(shi)中，和(he)金(jin)屬(shu)(shu)接觸發生(sheng)反(fan)應(ying)的(de)物質可以(yi)是氣(qi)體(ti)，也(ye)可以(yi)是液(ye)體(ti)，所以(yi)化學(xue)(xue)(xue)腐蝕(shi)(shi)又(you)分(fen)為氣(qi)體(ti)腐蝕(shi)(shi)和(he)液(ye)體(ti)腐蝕(shi)(shi)兩(liang)種。

 在高溫下，或周(zhou)圍沒有(you)導電物(wu)質的(de)條(tiao)件下，金(jin)(jin)屬(shu)與(yu)空(kong)氣(qi)或其他其他發生(sheng)反(fan)(fan)應，表面生(sheng)成氧(yang)化物(wu)或其他化合(he)物(wu)的(de)現象，稱(cheng)為氣(qi)體(ti)腐蝕。自(zi)然界中(zhong)(zhong)，氣(qi)體(ti)腐蝕的(de)現象也是很多。例如(ru)，鐵在空(kong)氣(qi)中(zhong)(zhong)或氧(yang)氣(qi)中(zhong)(zhong)加(jia)熱時，表面會(hui)生(sheng)成鐵的(de)氧(yang)化物(wu)膜(mo)(mo)；鋁在空(kong)氣(qi)中(zhong)(zhong)會(hui)與(yu)氧(yang)氣(qi)反(fan)(fan)應，表面生(sheng)成一層氧(yang)化鋁薄膜(mo)(mo)。像這(zhe)樣(yang)，金(jin)(jin)屬(shu)與(yu)周(zhou)圍的(de)物(wu)質接觸發生(sheng)反(fan)(fan)應生(sheng)成了化合(he)物(wu)，我(wo)們(men)就(jiu)說(shuo)金(jin)(jin)屬(shu)被腐蝕了，生(sheng)成的(de)化合(he)物(wu)（膜(mo)(mo)）就(jiu)是腐蝕的(de)產物(wu)（常稱(cheng)作銹）。

金(jin)屬(shu)在不(bu)導(dao)電的(de)(de)液(ye)(ye)體里的(de)(de)腐(fu)蝕(shi)也是一種化(hua)(hua)(hua)學(xue)腐(fu)蝕(shi)，叫(jiao)做(zuo)液(ye)(ye)體腐(fu)蝕(shi)。銀(yin)(yin)可與碘發(fa)生液(ye)(ye)體腐(fu)蝕(shi)。例如把碘溶(rong)(rong)(rong)解于乙(yi)(yi)醚(mi)中(zhong)(zhong)，制成(cheng)碘的(de)(de)乙(yi)(yi)醚(mi)溶(rong)(rong)(rong)液(ye)(ye)。乙(yi)(yi)醚(mi)是一種有機物(wu)(wu)(wu)，不(bu)能(neng)導(dao)電。把銀(yin)(yin)塊(kuai)投(tou)入溶(rong)(rong)(rong)液(ye)(ye)中(zhong)(zhong)，溶(rong)(rong)(rong)解了的(de)(de)碘能(neng)夠與銀(yin)(yin)反(fan)應(ying)(ying)(ying)，在銀(yin)(yin)的(de)(de)表面生產碘化(hua)(hua)(hua)銀(yin)(yin)膜。石油(you)(you)中(zhong)(zhong)往往含有硫(liu)、硫(liu)化(hua)(hua)(hua)氫(qing)及(ji)某些含硫(liu)的(de)(de)有機物(wu)(wu)(wu)，石油(you)(you)中(zhong)(zhong)還含有少(shao)量(liang)水，這(zhe)少(shao)量(liang)的(de)(de)水一般不(bu)能(neng)與硫(liu)的(de)(de)化(hua)(hua)(hua)合物(wu)(wu)(wu)形成(cheng)導(dao)電溶(rong)(rong)(rong)液(ye)(ye)，但它卻能(neng)加速硫(liu)的(de)(de)化(hua)(hua)(hua)合物(wu)(wu)(wu)與金(jin)屬(shu)發(fa)生化(hua)(hua)(hua)學(xue)反(fan)應(ying)(ying)(ying)，成(cheng)為反(fan)應(ying)(ying)(ying)的(de)(de)催化(hua)(hua)(hua)劑(ji)。例如，硫(liu)化(hua)(hua)(hua)氫(qing)可與鐵、鉛、銅、汞、銀(yin)(yin)等反(fan)應(ying)(ying)(ying)，生成(cheng)這(zhe)些金(jin)屬(shu)的(de)(de)硫(liu)化(hua)(hua)(hua)物(wu)(wu)(wu)，單質硫(liu)也可與銅、汞、銀(yin)(yin)等金(jin)屬(shu)反(fan)應(ying)(ying)(ying)，所以儲存(cun)石油(you)(you)的(de)(de)容(rong)器(qi)上部(bu)或蓋子往往被硫(liu)化(hua)(hua)(hua)氫(qing)腐(fu)蝕(shi)。在煉(lian)油(you)(you)廠，常采用(yong)耐硫(liu)化(hua)(hua)(hua)氫(qing)腐(fu)蝕(shi)的(de)(de)鋁(lv)箔來保護這(zhe)些容(rong)器(qi)。

化學腐蝕比較簡單，而且只在(zai)(zai)某些(xie)特定(ding)條件下才會發生。在(zai)(zai)生產和(he)日常生活中普遍存在(zai)(zai)的(de)、破壞最嚴重的(de)是電化學腐蝕，它是金屬(shu)常患的(de)“風濕病”。

電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)化腐(fu)(fu)(fu)(fu)蝕(shi)是指(zhi)金(jin)(jin)(jin)屬(shu)與電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)解質溶(rong)液(ye)作(zuo)用所(suo)發生的(de)(de)(de)(de)腐(fu)(fu)(fu)(fu)蝕(shi)。它的(de)(de)(de)(de)特點(dian)是在腐(fu)(fu)(fu)(fu)蝕(shi)過(guo)程(cheng)中有電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流產(chan)生，這是金(jin)(jin)(jin)屬(shu)表(biao)面(mian)發生腐(fu)(fu)(fu)(fu)蝕(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池作(zuo)用的(de)(de)(de)(de)結(jie)果。通(tong)常(chang)在電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)化腐(fu)(fu)(fu)(fu)蝕(shi)中規定，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)較低的(de)(de)(de)(de)金(jin)(jin)(jin)屬(shu)為陽(yang)極(ji)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)較高(gao)的(de)(de)(de)(de)金(jin)(jin)(jin)屬(shu)為陰(yin)極(ji)。當兩種電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)不(bu)同(tong)的(de)(de)(de)(de)金(jin)(jin)(jin)屬(shu)相(xiang)接(jie)觸，或(huo)同(tong)種金(jin)(jin)(jin)屬(shu)的(de)(de)(de)(de)不(bu)同(tong)的(de)(de)(de)(de)部位(wei)(wei)具(ju)有不(bu)同(tong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)時，它們(men)侵(qin)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)解質溶(rong)液(ye)（潮濕氣(qi)體、海(hai)水(shui)、酸、堿(jian)、鹽(yan)的(de)(de)(de)(de)水(shui)溶(rong)液(ye)或(huo)土(tu)壤(rang)等）后會(hui)變形成腐(fu)(fu)(fu)(fu)蝕(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池。結(jie)果，作(zuo)為陽(yang)極(ji)的(de)(de)(de)(de)（電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)低的(de)(de)(de)(de)）金(jin)(jin)(jin)屬(shu)，由于不(bu)斷失(shi)去電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)子(zi)(zi)并(bing)將自(zi)己的(de)(de)(de)(de)離子(zi)(zi)投入(ru)溶(rong)液(ye)而(er)被(bei)腐(fu)(fu)(fu)(fu)蝕(shi)，而(er)作(zuo)為陰(yin)極(ji)的(de)(de)(de)(de)（電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)高(gao)的(de)(de)(de)(de)）金(jin)(jin)(jin)屬(shu)由于僅(jin)起著傳遞電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)子(zi)(zi)的(de)(de)(de)(de)作(zuo)用，本(ben)身(shen)沒有發生腐(fu)(fu)(fu)(fu)蝕(shi)及(ji)其他變化。