鋼材磷酸鹽處理之電化學監測

Monitor of Electrochemical Behavior for Phosphatizing Treatment of Steels

本研究利用恆電位儀監測鋼材表面在磷酸鹽處理時的即時電位變化，依此反應曲線可控制磷酸鹽皮膜之品質。研究結果顯示鋼材與磷酸鹽溶液間之反應為電化學變化，由曲線之趨勢，可大略區分為5個階段：(1)活性腐蝕期，曲線朝向卑電位變化，(2)磷酸鹽皮膜晶粒核化期，此時電位保持水平和恆定，約在－570毫伏保持約1～3分鐘，(3)晶粒成長期，電位曲線指向貴重方向上昇，(4)晶粒完全成長期，電位又趨平穩，約在－450毫伏和(5)溶解期，電位朝卑向緩降。

This study uses a potentiostat to monitor the real-time open circuit potential (OCP) of steel surface during phosphatizing treatment. According to the reaction curve, the quality of the phosphating film can be controlled. The results show that the reaction between steel and phosphatizing solution follows an electrochemical mechanism. On account of the tendency of the curves, the mechanism can be divided into five stages: (1)active corrosion stage, the curve goes down to the active direction immediately, (2)crystal nucleation stage, the ocp keeps constant -570mv, for about 1~3 min, (3)crystal growth stage, the ocp curve moves to the noble direction, (4)crystal complete coalescence stage, the ocp stays constant, and (5)siight dissolution stage, the ocp goes down slowly again.