石墨的添加對碳化矽粒子強化銅基複合材料之耐腐蝕行為的影響研究

Effect of Graphite Additions on the Corrosion Resistance Behavior of SiC Particulate-Reinforced Copper Matrix Composites

本研究係利用粉末熱壓燒結技術，製作Cu、Cu-10 vol.% SiC及添加不同石墨含量（2.5～7.5 vol.%）之Cu/10 vol.% SiC / Graphite之銅金屬基複合材料，探討碳化矽顆粒及石墨的添加對銅金屬基合材料在3.5 wt.%氯化鈉（NaCl）水溶液中（PH 6.7）之耐腐蝕行為的影響效應。腐蝕試驗包括浸漬試驗及電化學極化量測。實驗結果顯示，銅基複合材料之鈍化層的形成會隨添加石墨含量的增加而趨於不明顯，其中鈍化層保護性以純銅之最佳，而含有7.5 vol.% 石墨之Cu-10 vol.% SiC-7.5 vol.% Graphite複材最差。由材料腐蝕表面觀察，發現在銅基材SiC界面以及在銅基材與石墨邊界，分別產生了間隙腐蝕與伽凡尼腐蝕，而使得SiC顆粒易於剝離及降低了銅基材孔蝕的抵抗性。此外，氧氣的存在會使所有材料之腐蝕速率增加，不管含有強化相的複材或未強化的純銅，在充有空氣的氯鹽溶液均比在除氯的氯鹽溶液中有更高的腐蝕速率。腐蝕浸漬試驗之重量損失隨浸漬時間增加而增大，同時含有強化相的銅金屬基複材均比純銅有較大的重量損失，而且會隨石墨添加量之增加而增大。

The corrosion resistance behavior of Cu/10 vol.% SiC copper matrix composites with different graphite volume fractions ranging from 2.5 to 7.5 vol.% was investigated in 3.5 wt.%sodium chloride (NaCl) aqueous solution and compared to the behavior of pure copper. All the materials were fabricated by a hot pressing technique. Both salt immersion and electrochemical polarization measurements were made, and the surface morphology and composition after corrosion tests were examined. The results indicate that the graphite addition had an adverse effect on the formation of the surface passive film; Cu / 10 vol.% SiC / 7.5 vol.% Graphite was the worst, whereas pure copper possessed the best protective surface film. Evidence further showed that the composites Cu/SiC/Graphite exhibited crevice attack at the copper matrix-SiC reinforcement interface and galvanic corrosion attack at the graphite-copper matrix boundary, which made SiC particles peeling and copper matrix pitting seriously. Moreover, the presence of dissolved oxygen enhanced the corrosion severity, the corrosion rate of both reinforced composites and unreinforced pure copper in aerated chloride solution was higher than that in deaerated chloride solution. In addition, it was also found that the composites exhibited higher corrosion loss over the pure copper, and weight loss increased with increasing graphite contents and exposure time.