腐蝕抑制劑對鋼材在添加次氯酸鹽模擬海水中之影響

Effect of Corrosion Inhibitors on Corrosion Rate of Mild Steel in 3.5%NaCl Solution and Artificial Seawater Containing NaClO

次氯酸鈉（NaClO）雖可消除海水中巨污生物及微污生物所造成的鋼材腐蝕，但此種強氧化劑會導致環境中氯的殘留，進而引發更嚴重的腐蝕。本研究選用兩種抑制劑，評估鋼鐵在含不同濃度（0.1～30ml/l）NaClO（有效氯6%）之3.5% NaCl及人造海水中之腐蝕抑制效率。鉻酸鈉為有效鈍化劑，在含各種濃度之NaClO 3.5%NaCl溶液及人造海水，加入鉻酸鈉促使鋼材腐蝕電位上升並減緩腐蝕速率。石灰是陰極抑制劑，NaClO濃度高達10ml/l時石灰抑制效果不佳。

NaClO is widely used in marine environments to eliminate the macroorganisms and microorganisms that possibly induce the localized corrosion due to fouling problems. Serving as a strong oxidizing agent, NaClO may decompose and cause residual chlorine in the solution, thus results in further corrosion. In this study, two corrosion inhibitors were chosen to evaluate their inhibition efficiencies for steel used in 3.5% NaCl solution and artificial seawater containing various concentrations (0.1-30 ml/l) of NaClO with effective chlorine concentration at 6%. The results show that the corrosion rate of steel increases with increasing the concentration of NaClO. Sodium chromate is an effective passivator for all test solutions. The corrosion potentials of steel move up to more noble (positive) value in the presence of chromate to retard corrosion rate. Lime is a cathodic inhibitor. However it is not suitable to apply lime in the aqueous solution containing concentrate NaClO up to 10ml/l.