不同加鋅處理條件之敏化304不銹鋼在模擬沸水式反應器環境中的電化學特性研究

Electrochemical Behavior of Type 304 Stainless Steels Treated with Different Type of Zn Addition in Simulated Boiling Water Reactor Environments

核能電廠沸水式反應器在長期運轉後，組件材料均易出現沿晶應力腐蝕龜裂的問題。為了解決此問題，核能業界大多採用加氫水化學技術，然而此技術在使用後卻發現會有管路輻射劑量增加的副作用。氧化鋅添加技術會置換不銹鋼組件氧化膜表層中的放射性鈷元素，可能因而改變組件氧化層的結構與性質，進而對組件的電化學腐蝕電位產生影響。因此本研究針對敏化304不銹鋼進行不同條件的加鋅處理，其後對試片進行表面分析，並在模擬沸水式反應器的高溫純水環境下進行動態電位極化掃描，以了解加鋅處理對敏化304不銹鋼電化學腐蝕行為的影響。結果顯示只有在1 ppm的加鋅條件下，才會有明顯的鋅離子置換不銹鋼氧化層元素現象發生，但在所有條件的加鋅處理試片下，均無法去觀察到加鋅處理具有抑制304不銹鋼腐蝕的效益存在。

As the boiling water reactors age, incidents of intergranular stress corrosion cracking become more prevailing than ever. The technique of zinc addition is able to enhance the exchange of zinc and cobalt on the oxide layer of structural component surfaces. This may thus alter the structure and property of the oxide and result in a shift in corrosion potential. In the current study, surface analyses were carried out to examine the structure of the oxide layer on Type 304 stainless steels (SS), and electrochemical polarization tests were then performed to investigate the effect of Zn addition on corrosion mitigation of 304 SS in simulated boiling water reactor environments. Test results showed that the specimen treated with 1 ppm ZnO could experience the exchange of zinc ion and metal ion on the surface oxide, but none of the treated 304 SS specimens revealed any significant reduction in corrosion rate in the test environments.