以(yi)(yi)(yi)管(guan)(guan)道(dao)作為陽極(ji)，從外部通入電(dian)(dian)(dian)(dian)(dian)流，一(yi)般(ban)將加速(su)(su)(su)腐(fu)蝕(shi)(shi)，腐(fu)蝕(shi)(shi)電(dian)(dian)(dian)(dian)(dian)流隨陽極(ji)極(ji)化(hua)(hua)而增大(da)。但是對(dui)可(ke)以(yi)(yi)(yi)鈍化(hua)(hua)的(de)(de)(de)金屬則會出現另一(yi)情況(kuang)，當電(dian)(dian)(dian)(dian)(dian)位(wei)(wei)隨電(dian)(dian)(dian)(dian)(dian)流上(shang)(shang)升，達到致鈍電(dian)(dian)(dian)(dian)(dian)位(wei)(wei)后(hou)，腐(fu)蝕(shi)(shi)電(dian)(dian)(dian)(dian)(dian)流急速(su)(su)(su)下降，甚(shen)至可(ke)下降幾萬(wan)倍，以(yi)(yi)(yi)后(hou)隨電(dian)(dian)(dian)(dian)(dian)位(wei)(wei)上(shang)(shang)升，電(dian)(dian)(dian)(dian)(dian)流不(bu)變，直到過鈍區(qu)為止。利用(yong)(yong)這個原理Edleanu 首(shou)先提出陽極(ji)保(bao)(bao)護的(de)(de)(de)概念，以(yi)(yi)(yi)需(xu)要(yao)保(bao)(bao)護的(de)(de)(de)設(she)備(bei)(bei)為陽極(ji)，導入電(dian)(dian)(dian)(dian)(dian)流，使電(dian)(dian)(dian)(dian)(dian)位(wei)(wei)保(bao)(bao)持在鈍化(hua)(hua)區(qu)的(de)(de)(de)中段（以(yi)(yi)(yi)免波動時進入活化(hua)(hua)區(qu)），腐(fu)蝕(shi)(shi)速(su)(su)(su)率可(ke)保(bao)(bao)持很低(di)值，通入的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)流就表示設(she)備(bei)(bei)的(de)(de)(de)腐(fu)蝕(shi)(shi)速(su)(su)(su)率。這種(zhong)(zhong)方法需(xu)要(yao)一(yi)臺(tai)恒電(dian)(dian)(dian)(dian)(dian)位(wei)(wei)儀(yi)，用(yong)(yong)以(yi)(yi)(yi)控制設(she)備(bei)(bei)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)位(wei)(wei)。因為它只適用(yong)(yong)于(yu)(yu)接觸鈍化(hua)(hua)溶液的(de)(de)(de)可(ke)鈍化(hua)(hua)金屬，所以(yi)(yi)(yi)用(yong)(yong)途受限制。工(gong)業(ye)上(shang)(shang)已用(yong)(yong)于(yu)(yu)處(chu)理硫酸(suan)、磷酸(suan)、碳(tan)酸(suan)氫銨生產(chan)液、硝(xiao)銨混肥等的(de)(de)(de)不(bu)銹鋼(gang)(gang)或碳(tan)鋼(gang)(gang)制的(de)(de)(de)各(ge)種(zhong)(zhong)管(guan)(guan)道(dao)設(she)備(bei)(bei)。