低磷含量鎳磷合金電鍍層之耐蝕性與機械性質研究

The Study of Corrosion Resistance and Mechanical Properties of Low Phosphorous Content Nickel Plated Coatings

一般鎳磷合金電鍍層的內應力隨鍍層磷含量的增加而上升，造成鍍層與底材附著性不佳，在電鑄方面的應用有困難。本研究利用鍍鎳液添加微量含磷化合物的方式，進行低磷含量的鎳磷合金層電鍍，來改善鍍鎳層特性。為了解低磷含量鍍鎳層的鍍層特性，除進行鍍鎳層機械特性與耐磨耗性測試外，並利用電化學動電位極化曲線法，測量鍍層在含氟離子溶液中的耐蝕特性。研究結果發現低磷含量（< 1 wt.%）的鎳磷合金鍍層的內應力極低，鍍層經300℃熱處理後不軟化，硬度維持為300 ~ 350 HV，高於一般純鎳鍍層的硬度（200 ~ 250 HV）；經砂輪耐磨耗測試，鎳磷合金鍍層磨耗重量損失僅為純鎳鍍層之56%。耐腐蝕特性方面，鎳磷合金鍍層極化曲線顯現鈍化區，鈷鎳合金鍍層則未顯現鈍化區域，浸泡實驗的結果亦顯現鎳磷合金鍍層的耐蝕性較鈷鎳合金鍍層為優。

The internal stress of Nickel-Phosphorous (Ni-P) plated layer increases with increasing phosphorous content. A high internal stress would cause deterioration of adhesion between the plated coating and the base metal, leading to subsequent problems in electroforming applications. In this study, a low phosphorous content nickel plating bath was used to produce low P content coatings and to improve the physical properties of the coatings. The mechanical properties and anti-wearing resistance of the coatings were tested, and the potentiodynamic polarization analysis was conducted to measure the corrosion resistance of the plated coating in a fluoride ion containing solution. Test results showed that the internal stress of the Ni-P coating of low-P content was extremely low and the hardness was maintained at 300 ~ 350 HV after being heattreated at 300 ℃. Under the same heat treatment, the hardness of a pure Ni plated coating decreased to 200 ~ 250 HV. Therefore, the weight loss of the Ni-P coating was only 56% of that of the pure Ni coating in the wearing test using a Taber Type Abrasion Tester. A quasi-passive region was noticed in the potentiodynamic polarization curve of the Ni-P coating, but it was not shown in that of a cobalt-nickel coating. The immersion test in a fluoride ion containing solution also demonstrated that the Ni-P coating was superior to the cobalt-nickel coating.