脈衝電鍍三價鉻製備鉻–碳合金鍍層之研究

Characteristics of Trivalent Chromium-carbon Alloys Catings by Using Pulse Electroplating

本研究之目的主要為提升鉻-碳鍍層的膜厚，以得到高導電性與耐蝕性之鉻-碳鍍層。實驗中以Duty Cycle與頻率為操作參數，對不同頻率及Duty Cycle所獲得的鍍層進行表面形貌、結構與組成、成分及耐蝕性檢測分析。實驗結果顯示，在表面均有裂紋，結構組成為Cr2C3、Cr7C3與Cr23C6，在3.5% NaCl水溶液之腐蝕電流密度為5×10-7 A/cm2，顯示此鍍層對基材有一定的保護程度。此外，在Duty Cycle 50%、500Hz操作條件下，相較於直流電鍍鉻碳合金的效率提高為三到四倍。

In this study, the trivalent chromium carbide coatings which have high electro-conductive and corrosion resistance were prepared using pulse electroplating process. The different operated conditions such as duty cycle and frequency were controlled in this work and the characteristics including morphology, phase composition, chemical composition and corrosion resistance of coatings formed with different parameters were also analyzed. The experimental result showed that there are cracks on the surface of coatings caused by the residual stress of Cr-C alloy coatings. The structure analyzes indicated that the main phase compositions included Cr23C6 and Cr7C3. The corrosion resistance of Cr-C coatings was measured by using a 3.5% NaCl(aq) solution, the result revealed that the corrosion current density of Cr-C coatings achieved about 5×10-7 A/dm2, this demonstrated that the Cr-C coatings has the good protection to the parent metal. The Cr-C coatings formed under the duty cycle at 50% and 500 Hz has an excellent efficiency about three to four times than that of direct current process.