不銹鋼罅隙腐蝕機理研究

The Mechanism of The Crevice Corrosion of Stainless Steel

罅隙腐蝕是造成不銹鋼嚴重腐蝕損害之主要原因。世界各國均積極從事罅隙腐蝕防治研究工作，然由於受到測試裝置及測試技巧限制，尚未能完全掌握罅隙腐蝕反應機理，本研究之目的即針對此一研究需求，開發設計適宜之罅隙腐蝕電化學研究測試裝置，在甚薄之罅隙液內，精心裝設測試電極、輔助電極及參考電極，並藉調整薄膜厚度及控制罅隙腐蝕因子，俾能執行各項AC及DC極化測試研究，此測試裝置所具功能尚可直接藉光學顯微影像解析技巧，進行真實時間罅隙腐蝕起始、孕育及生長階段之觀察，蝕孔大小、深度及分佈情形研究。本文所進行之罅路隙腐蝕重要研究項目包括、罅隙液溶氧消耗速率、氯離子滲透速率、pH效應、溫度效應、直接研判被動膜崩破程度、罅隙液臨界條件等，經一系列實驗結果証實本研究所設計之罅隙腐蝕測試裝置能滿足測試所需具備之條件，可整體考量所有直接及間接影響罅隙腐蝕因子，對進行罅隙腐蝕機理研究及腐蝕防治技術開發有直接助益。

Stainless steel may be servely damaged by crevice corrosion. The mechanism of crevice corrosion of 304 stainless in chloride containing environments usually occurs by the formation of oxygen concentration cell, followed by crevice solution acidification and a build-up of chloride ions within the crevice. A novel electrochemical crevice cell has been designed and able Io carry out in-situ AC and DC polarization measurements to examine the basic processes involved in the mechanism of crevice corrosion. The crevice cell has been used to study the depletion rate of oxygen within crevice, the permeation rate of chloride, and the effect of the pH value, oxygen and chloride concentrations on the ability of a passive film to resist the initiation and propagation of crevice corrosion in the microenvironment that exists in a crevice.