利用電化學阻抗光譜探討熱浸鍍鋅鋼板塗裝之防蝕機理

An Electrochemical Impedance Spectroscopy Study of the Corrosion Prevention Mechanism of Painted Galvanized Steel

本研究以熱浸鍍鋅鋼板為基材，分別施以5種不同之前處理，然後噴塗環氧樹脂為面漆製成試樣，在3.5wt % NaCl溶液中總計進行21天之試驗。在試驗期間定時取樣測定其電化阻抗光譜，實驗結果發現，試樣浸泡初期，塗裝之保護主要為阻絕性質，其所展現之電化學行為屬電容效應；隨浸泡時間增長，漆膜逐漸顯出退化現象，由電化學阻抗光譜圖證明，除了以代銹底漆前處理之試樣以外，其它試樣之腐蝕反應均受擴散控制之影響。

Five pretreatment methods were used to prepare the surface of galvanizd steels then painted with epoxy resin respectively. The coated specimens were tested in 3.5wt% NaCl solution by Electrochemical Impedance Spectroscopy (EIS) for 21 days totally. EIS results showed that the protection mechanism of the paint films was mainly due to their insulating and capacitance effects in the beginning. However, the paint films were degraded gradually as the immersion time increased. In addition, EIS also showed that corrosion reactions at the paint films/substrate interface were diffusion controlled except for those treated with eash primer.