以(yi)管道(dao)(dao)作為陽(yang)極(ji)(ji)(ji)，從外部通(tong)入電(dian)(dian)(dian)(dian)流(liu)，一般將(jiang)加速(su)腐(fu)(fu)蝕(shi)，腐(fu)(fu)蝕(shi)電(dian)(dian)(dian)(dian)流(liu)隨(sui)陽(yang)極(ji)(ji)(ji)極(ji)(ji)(ji)化(hua)而增(zeng)大。但(dan)是(shi)對可(ke)以(yi)鈍(dun)化(hua)的(de)金(jin)屬則會出(chu)現另一情況，當電(dian)(dian)(dian)(dian)位隨(sui)電(dian)(dian)(dian)(dian)流(liu)上升(sheng)，達(da)到(dao)致鈍(dun)電(dian)(dian)(dian)(dian)位后(hou)(hou)，腐(fu)(fu)蝕(shi)電(dian)(dian)(dian)(dian)流(liu)急速(su)下(xia)降，甚至可(ke)下(xia)降幾萬倍，以(yi)后(hou)(hou)隨(sui)電(dian)(dian)(dian)(dian)位上升(sheng)，電(dian)(dian)(dian)(dian)流(liu)不(bu)變(bian)，直到(dao)過鈍(dun)區(qu)為止。利用這(zhe)個原理Edleanu 首先提出(chu)陽(yang)極(ji)(ji)(ji)保(bao)(bao)(bao)護(hu)的(de)概念，以(yi)需要(yao)保(bao)(bao)(bao)護(hu)的(de)設(she)備(bei)為陽(yang)極(ji)(ji)(ji)，導入電(dian)(dian)(dian)(dian)流(liu)，使電(dian)(dian)(dian)(dian)位保(bao)(bao)(bao)持在鈍(dun)化(hua)區(qu)的(de)中段（以(yi)免波動時進入活(huo)化(hua)區(qu)），腐(fu)(fu)蝕(shi)速(su)率(lv)可(ke)保(bao)(bao)(bao)持很低值，通(tong)入的(de)電(dian)(dian)(dian)(dian)流(liu)就表示設(she)備(bei)的(de)腐(fu)(fu)蝕(shi)速(su)率(lv)。這(zhe)種方法需要(yao)一臺恒電(dian)(dian)(dian)(dian)位儀，用以(yi)控制(zhi)設(she)備(bei)的(de)電(dian)(dian)(dian)(dian)位。因(yin)為它只(zhi)適用于接觸鈍(dun)化(hua)溶液的(de)可(ke)鈍(dun)化(hua)金(jin)屬，所以(yi)用途(tu)受限制(zhi)。工業(ye)上已用于處理硫(liu)酸、磷(lin)酸、碳酸氫銨生(sheng)產(chan)液、硝銨混肥等的(de)不(bu)銹鋼或碳鋼制(zhi)的(de)各種管道(dao)(dao)設(she)備(bei)。