以(yi)管(guan)道(dao)作為(wei)陽(yang)(yang)(yang)極(ji)，從外部(bu)通入電(dian)(dian)(dian)(dian)(dian)(dian)流，一般將加速(su)腐(fu)蝕，腐(fu)蝕電(dian)(dian)(dian)(dian)(dian)(dian)流隨(sui)陽(yang)(yang)(yang)極(ji)極(ji)化(hua)而增大。但是對可(ke)以(yi)鈍(dun)化(hua)的(de)金屬(shu)則會出現另一情(qing)況，當電(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)隨(sui)電(dian)(dian)(dian)(dian)(dian)(dian)流上升，達到致鈍(dun)電(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)后，腐(fu)蝕電(dian)(dian)(dian)(dian)(dian)(dian)流急(ji)速(su)下(xia)降，甚至可(ke)下(xia)降幾萬倍，以(yi)后隨(sui)電(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)上升，電(dian)(dian)(dian)(dian)(dian)(dian)流不變，直到過鈍(dun)區(qu)為(wei)止。利用這個原理Edleanu 首先提出陽(yang)(yang)(yang)極(ji)保(bao)(bao)護(hu)的(de)概念，以(yi)需(xu)要(yao)保(bao)(bao)護(hu)的(de)設(she)備(bei)為(wei)陽(yang)(yang)(yang)極(ji)，導入電(dian)(dian)(dian)(dian)(dian)(dian)流，使(shi)電(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)保(bao)(bao)持(chi)在鈍(dun)化(hua)區(qu)的(de)中段（以(yi)免波動時(shi)進入活化(hua)區(qu)），腐(fu)蝕速(su)率(lv)可(ke)保(bao)(bao)持(chi)很低值(zhi)，通入的(de)電(dian)(dian)(dian)(dian)(dian)(dian)流就(jiu)表示設(she)備(bei)的(de)腐(fu)蝕速(su)率(lv)。這種方法(fa)需(xu)要(yao)一臺(tai)恒(heng)電(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)儀，用以(yi)控制設(she)備(bei)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)。因為(wei)它只(zhi)適用于接觸(chu)鈍(dun)化(hua)溶液的(de)可(ke)鈍(dun)化(hua)金屬(shu)，所以(yi)用途受限制。工業上已(yi)用于處理硫酸(suan)(suan)、磷酸(suan)(suan)、碳(tan)酸(suan)(suan)氫銨(an)生(sheng)產液、硝銨(an)混肥等的(de)不銹鋼或碳(tan)鋼制的(de)各種管(guan)道(dao)設(she)備(bei)。