電解液的加熱是以直流電為電源在電解液中進行的，適用于表面加熱淬火的電解液很多，一般采用質量分數為8％～10％的Na2CO3水溶液。
電(dian)(dian)(dian)(dian)解(jie)液表(biao)面(mian)淬火(huo)(huo)原理是(shi)將工(gong)(gong)件(jian)置于(yu)電(dian)(dian)(dian)(dian)解(jie)液中（局(ju)部(bu)或全部(bu)）作為陰極，金(jin)屬電(dian)(dian)(dian)(dian)解(jie)槽作為陽(yang)極。電(dian)(dian)(dian)(dian)路(lu)接通(tong)后，電(dian)(dian)(dian)(dian)解(jie)液發生(sheng)電(dian)(dian)(dian)(dian)離，在陽(yang)極上放出氧，在陰極上放出氫。氫圍(wei)繞工(gong)(gong)件(jian)形成氣膜，產生(sheng)很大(da)的電(dian)(dian)(dian)(dian)阻(zu)，通(tong)過的電(dian)(dian)(dian)(dian)流轉化為熱能將工(gong)(gong)件(jian)表(biao)面(mian)迅速加熱到(dao)臨(lin)界點以上溫度。電(dian)(dian)(dian)(dian)路(lu)斷開氣膜消失，加熱的工(gong)(gong)件(jian)在電(dian)(dian)(dian)(dian)解(jie)液中即實現淬火(huo)(huo)冷卻。此方法(fa)所用設備簡單，淬火(huo)(huo)變形小，適用于(yu)形狀簡單、小工(gong)(gong)件(jian)的批(pi)量生(sheng)產。
電(dian)(dian)(dian)解液溫度(du)(du)(du)不(bu)能超過60℃。溫度(du)(du)(du)過高，氫氣膜不(bu)穩定，影響(xiang)加(jia)(jia)熱(re)(re)過程(cheng)，還會(hui)加(jia)(jia)速(su)溶(rong)液的(de)(de)蒸發。常(chang)用電(dian)(dian)(dian)壓為(wei)160～180V，最高不(bu)超過260V，電(dian)(dian)(dian)流(liu)(liu)密度(du)(du)(du)的(de)(de)范(fan)圍是4～10A／c㎡，通(tong)常(chang)可(ke)選用6A／c㎡。電(dian)(dian)(dian)流(liu)(liu)密度(du)(du)(du)過大時，加(jia)(jia)熱(re)(re)速(su)度(du)(du)(du)快，淬硬層(ceng)薄。在加(jia)(jia)熱(re)(re)過程(cheng)中，應將工(gong)件(jian)的(de)(de)位置加(jia)(jia)以(yi)固(gu)定，否則會(hui)造成(cheng)電(dian)(dian)(dian)流(liu)(liu)密度(du)(du)(du)的(de)(de)變化，使淬硬層(ceng)質量惡化。加(jia)(jia)熱(re)(re)時間可(ke)通(tong)過試驗確(que)定。工(gong)件(jian)在電(dian)(dian)(dian)解液中可(ke)采用端部自由加(jia)(jia)熱(re)(re)、端部絕緣加(jia)(jia)熱(re)(re)、回轉加(jia)(jia)熱(re)(re)和連續加(jia)(jia)熱(re)(re)等方式(shi)。
