陰極防護對鋼材抗蝕及機械性能之影響

A Study on the Protection of Steel Using Cathodic Potential in 3.5% NaCl Solution

中碳鋼棒在25℃及3.5% NaCl溶液中經外加電位測試，電位在-0.75v(SCE)時即達臨界保護電位值（critical protection potential）。未加電位保護之鋼棒試體浸泡30天後測出之腐蝕速率為5 mpy。鋼筋之機械強度因腐蝕面影響而有明顯損失，本研究顯示陰極防護並不造成鋼棒之機械性能的損失，即在3.5% NaCl溶液中並不因氫氣之生成而損失鋼筋之強度與延展性。此外，外加電位以-0.75 ~ -0.8V(SCE)為宜。

The critical protection potential for medium carbon steel specimens in 3.5% NaCl solution at 25℃ was evaluated, and -0.75 V (SCE) critical protection potential was obtained. After 30-day immersion testing, the corrosion rate of specimens without protection potential was 5 mpy. Mechanical properties of corroded specimens show significant degradation. On the other hand, specimens protected by impressed current show no evident changes in mechanical properties, i.e., specimens under impressed current protection in the 3.5% NaCl solution do not lose their strength and ductility because of hydrogen effect. According to this study, the optimum range of protection potential is -0.75V ~ -0.80V (SCE).