沸水式反應器水模擬環境中過氧化氫於氧化鋯被覆304不銹鋼表面之電化學行為分析

The Influence of ZrO2 Treatment on the Electrochemical Behavior of Hydrogen Peroxide on Type 304 Stainless Steels in High Temperature Water

本研究沿用過去發展的抑制性氧化鋯被覆技術，探討模擬沸水式反應器環境中，主要氧化劑（如氧與過氧化氫）在被覆前後304不銹鋼試片表面的電化學行為，本次的研究標的為過氧化氫。本研究採行電化學極化掃瞄（electrochemical polarization）測試以決定不銹鋼的腐蝕電位與腐蝕電流密度，以及過氧化氫還原反應的交換電流密度與塔弗常數。我們並利用掃瞄式電子顯微鏡、拉曼頻譜分析試片的表面狀態與結構。氧化鋯被覆的防蝕效率則依高溫環境中極化掃瞄分析的結果判定。本研究的實驗結果顯示，氧化鋯被覆對於試片的腐蝕電位並無明顯影響，但對於過氧化氫還原反應的交換電流密度及試片的腐蝕電流密度則有抑制的效果，顯示本被覆技術確實有減緩過氧化氫還原反應速率的效用。

Following our earlier work on exploring the electrochemical characteristics of important oxidizing species on zirconium oxide (ZrO2) treated Type 304 stainless steels (SSs), we targeted on the characteristics of hydrogen peroxide, which is another strongly oxidizing species in the reactor coolant other than oxygen, in this study. Tests were conducted to determine electrochemical parameters such as electrochemical corrosion potential (ECP), corrosion current density, exchange current density and Tafel constant of the reduction reaction of hydrogen peroxide on 304 SS specimens before and after the ZrO2 treatment. The surface morphologies of the treated and untreated specimens were examined by scanning electron microscopy and Raman spectra. Furthermore, the corrosion mitigation efficiency of ZrO2 treatment was evaluated by electrochemical polarization tests in simulated BWR environments. Test results showed that there were no significant differences in ECP between the untreated and ZrO2 treated specimens in the test environments of various hydrogen peroxide concentrations. However, it was found via polarization analysis that the exchange current density of the reduction reaction on and the corrosion current density of the treated specimens were markedly lower than those on and of the untreated ones in the same environments. The ZrO2 treatment was able to deter the reduction rate of hydrogen peroxide on the Type 304 SS surface.