以(yi)(yi)管道作為(wei)陽極(ji)(ji)，從外(wai)部通入(ru)電(dian)(dian)(dian)(dian)流(liu)(liu)，一般將加速(su)腐(fu)蝕(shi)(shi)，腐(fu)蝕(shi)(shi)電(dian)(dian)(dian)(dian)流(liu)(liu)隨陽極(ji)(ji)極(ji)(ji)化(hua)(hua)(hua)而增(zeng)大(da)。但是對可以(yi)(yi)鈍化(hua)(hua)(hua)的金屬(shu)則(ze)會(hui)出現另一情況，當電(dian)(dian)(dian)(dian)位(wei)(wei)隨電(dian)(dian)(dian)(dian)流(liu)(liu)上(shang)升，達到(dao)致鈍電(dian)(dian)(dian)(dian)位(wei)(wei)后，腐(fu)蝕(shi)(shi)電(dian)(dian)(dian)(dian)流(liu)(liu)急速(su)下(xia)降，甚至可下(xia)降幾(ji)萬倍(bei)，以(yi)(yi)后隨電(dian)(dian)(dian)(dian)位(wei)(wei)上(shang)升，電(dian)(dian)(dian)(dian)流(liu)(liu)不變，直(zhi)到(dao)過鈍區(qu)(qu)為(wei)止。利(li)用(yong)這個原(yuan)理(li)Edleanu 首先提(ti)出陽極(ji)(ji)保(bao)(bao)護的概念，以(yi)(yi)需要(yao)保(bao)(bao)護的設(she)備(bei)為(wei)陽極(ji)(ji)，導入(ru)電(dian)(dian)(dian)(dian)流(liu)(liu)，使(shi)電(dian)(dian)(dian)(dian)位(wei)(wei)保(bao)(bao)持(chi)在(zai)鈍化(hua)(hua)(hua)區(qu)(qu)的中段（以(yi)(yi)免(mian)波動時進入(ru)活化(hua)(hua)(hua)區(qu)(qu)），腐(fu)蝕(shi)(shi)速(su)率可保(bao)(bao)持(chi)很低值(zhi)，通入(ru)的電(dian)(dian)(dian)(dian)流(liu)(liu)就表(biao)示設(she)備(bei)的腐(fu)蝕(shi)(shi)速(su)率。這種方法需要(yao)一臺恒(heng)電(dian)(dian)(dian)(dian)位(wei)(wei)儀，用(yong)以(yi)(yi)控制(zhi)(zhi)設(she)備(bei)的電(dian)(dian)(dian)(dian)位(wei)(wei)。因為(wei)它只適用(yong)于接觸鈍化(hua)(hua)(hua)溶液的可鈍化(hua)(hua)(hua)金屬(shu)，所以(yi)(yi)用(yong)途(tu)受限制(zhi)(zhi)。工業上(shang)已(yi)用(yong)于處理(li)硫酸(suan)、磷酸(suan)、碳酸(suan)氫銨生產(chan)液、硝銨混(hun)肥等的不銹(xiu)鋼或碳鋼制(zhi)(zhi)的各(ge)種管道設(she)備(bei)。