銲接沃斯田鐵系不銹鋼為乾貯系統中的密封鋼筒的主要材料，用於貯存用過核子燃料，台灣的乾貯場址選在沿海地區，環境充滿水氣與氯離子，再加上銲接過程中產生的高殘餘張應力以及受敏化現象影響，容易在不銹鋼筒表面引發氯離子誘發應力腐蝕龜裂，當生成的裂縫足以裂穿筒身，將影響用過核子燃料貯存的安全性，因此本實驗希望透過模擬室內乾貯的環境，探討以沃斯田鐵系不銹鋼304L、316L為基材銲接308L、316L銲條所製成不銹鋼U-bend銲件在不同溫度下、固定相對濕度40%的腐蝕行為，並研究相關的腐蝕劣化因子關係。
實驗結果顯示在溫度40、60及80oC下， 304L/308L與316L/316L SS試片在基材區域與熱影響區的腐蝕形貌以大面積孔蝕的聚合為主，在銲材區域則以枝晶狀腐蝕與孔蝕的聚合為主。根據腐蝕面積的定量計算結果顯示，在溫度40與60oC下，隨著實驗時間增加，腐蝕面積比例上升的速率較80oC的結果快，推測可能是因為在溫度80 oC下，腐蝕在短時間內達到其飽和值。孔蝕深度的量測結果顯示在三種不同溫度下，316L/316L SS試片的基材區域皆有深度超過60μm的孔蝕出現。

Welded austenitic stainless steels are considered as the materials for dry storage canisters used for interim storage of spent nuclear fuel. However, austenitic stainless steels are susceptible to chloride induced stress corrosion cracking (CISCC), particularly in the presence of residual tensile stress and sensitization due to the welding procedure. Dry storage systems located nearby a coastal site in Taiwan, thus high concentration of moisture and chloride salts in the atmospheric environment may introduce CISCC on the canisters surface. Therefore, the purpose of this study is to evaluate the corrosion behavior of candidate canisters materials in a salt fog test at different temperatures and constant relative humidity of 40% for 1500 hours.
According to the results of morphology observation, similar corrosion behavior was observed on three different materials at 40, 60 and 80oC. Pitting coalescence was the major corrosion behavior on the base metal and heat affected zone, and interdendritic corrosion and pitting coalescence were the primary corrosion behavior on the weld metal. Based on the calculation of corroded area, the percentage of corroded area increased significantly at 40 and 60oC with time, whereas it was slightly expanded at 80oC. Moreover, the depth of pits up to more than 60μm were measured on the base metal of 316L/316L SS specimens at three different temperatures.

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