以管道(dao)作為(wei)(wei)陽(yang)極(ji)，從(cong)外部通入電(dian)(dian)(dian)流(liu)(liu)，一般將加速腐(fu)蝕，腐(fu)蝕電(dian)(dian)(dian)流(liu)(liu)隨(sui)(sui)陽(yang)極(ji)極(ji)化(hua)而增大。但是對可(ke)以鈍(dun)化(hua)的(de)(de)(de)金屬(shu)則(ze)會出(chu)現另一情況，當(dang)電(dian)(dian)(dian)位(wei)(wei)隨(sui)(sui)電(dian)(dian)(dian)流(liu)(liu)上(shang)升，達(da)到致鈍(dun)電(dian)(dian)(dian)位(wei)(wei)后，腐(fu)蝕電(dian)(dian)(dian)流(liu)(liu)急(ji)速下降，甚(shen)至可(ke)下降幾萬倍，以后隨(sui)(sui)電(dian)(dian)(dian)位(wei)(wei)上(shang)升，電(dian)(dian)(dian)流(liu)(liu)不變，直到過鈍(dun)區(qu)為(wei)(wei)止。利用(yong)這個原理(li)Edleanu 首先提(ti)出(chu)陽(yang)極(ji)保(bao)護的(de)(de)(de)概念，以需(xu)要保(bao)護的(de)(de)(de)設(she)備(bei)為(wei)(wei)陽(yang)極(ji)，導入電(dian)(dian)(dian)流(liu)(liu)，使電(dian)(dian)(dian)位(wei)(wei)保(bao)持在鈍(dun)化(hua)區(qu)的(de)(de)(de)中段(duan)（以免波(bo)動時進入活化(hua)區(qu)），腐(fu)蝕速率可(ke)保(bao)持很(hen)低值，通入的(de)(de)(de)電(dian)(dian)(dian)流(liu)(liu)就(jiu)表(biao)示設(she)備(bei)的(de)(de)(de)腐(fu)蝕速率。這種(zhong)方法需(xu)要一臺恒(heng)電(dian)(dian)(dian)位(wei)(wei)儀，用(yong)以控制(zhi)設(she)備(bei)的(de)(de)(de)電(dian)(dian)(dian)位(wei)(wei)。因為(wei)(wei)它只適用(yong)于(yu)(yu)接(jie)觸鈍(dun)化(hua)溶液的(de)(de)(de)可(ke)鈍(dun)化(hua)金屬(shu)，所以用(yong)途受限制(zhi)。工(gong)業上(shang)已用(yong)于(yu)(yu)處理(li)硫酸(suan)(suan)、磷酸(suan)(suan)、碳(tan)酸(suan)(suan)氫銨生產液、硝銨混(hun)肥等的(de)(de)(de)不銹(xiu)鋼或碳(tan)鋼制(zhi)的(de)(de)(de)各種(zhong)管道(dao)設(she)備(bei)。