磷含量對無電鍍鎳在3.5wt%.氯化鈉溶液中腐蝕之影響

Effect of Phosphorus Content on the Corrosion Behavior of Electroless Nickel in 3.5wt%. NaCl Solution

本文探討以含次磷酸鈉為還原劑的鍍液在低碳鋼表面進行無電鍍鎳磷合金，鍍液在不同量還原劑及不同的pH值，析鍍出三種不同磷含量（2.3, 7.8和11.4wt%.）的鍍層，並以3.5wt%. 中性氯化鈉模擬海水溶液作為腐蝕環境，研究腐蝕行為。由電化學電位極化可知鍍層磷含量在7.8wt %.以上，具有形成被動態保護膜的能力。將試片在氮氣保護氣氛下進行400℃熱處理一小時及600℃熱處理一小時，抗蝕能力降低。浸漬兩個月的試片由SEM顯微察及EDS元素分析認定孔蝕並未穿透至底材。

The corrosion behaviors of electroless nickel with different phosphorus contents (2.3, 7.8and 11.4wt%.) in 3.5wt.% NaCl solution were studied. Based upon results of potentiodynamic polarization, the passive protection film will be formed as phosphorus content in electroless nickel exceeds 7.8 % wt. After heat treatment at 400℃ or 600℃ for 1 hour under nitrogen atmosphere, the anti-corrosion capability of electroless nickel is decreased obviously. Surface conditions were examined by SEM and EDS after dipping in NaCl solution for two months. The corrosion type is closely related to the phosphorus content.