無氧銅在不同濕度條件之大氣腐蝕

Atmospheric Corrosion of Oxygen-Free Copper under Various Relative Humidity

高純度無氧銅具良好腐蝕抗性，被考慮作為用過核燃料最終處置之廢棄物罐容器。銅廢棄物罐製造及裝載完成後，運送至最終處置場所封存前，處於暴露大氣環境時期。本研究探討無氧銅於乾淨室內空氣但不同溼度條件之腐蝕行為，選定30℃絕對溼度（29 g/m3 ）分別調整至相對溼度28%RH、45%RH、73%RH等三種條件進行長時間暴露實驗。定期取出實驗試片進行測量重量變化、記錄表面狀態、XRD分析腐蝕產物、以及SEM觀察表面形態等項目。結果顯示28%RH及45%RH皆在臨界相對濕度以下，未有明顯腐蝕現象，但是73%RH條件下則呈現顯著腐蝕行為，主要腐蝕產物為緻密性氧化亞銅（Cu2O）為主。

The oxygen-free copper has been considered as a canister material to dispose the spent nuclear fuels, due to its superior corrosion resistance. After the container has been fabricated and also the spent fuel has been encapsulated, the copper canisters will be transported to the geologic repository and disposed. From the initial fabrication and encapsulation to the final repository, however, the canister will be exposed to indoor air for a period of time. The purpose of this study was to investigate the corrosion behavior of the oxygen-free coppers exposed to indoor air with various levels of relative humidity. Three conditions of 28%RH, 45%RH, and 73%RH respectively, adjusted from the absolute humidity at 30℃, 29 g/m3, were chosen for a long term exposure. Specimens with different exposure time were examined by weight change, photographing, XRD, and SEM. The results showed that specimens with 28%RH and 45%RH revealed slow corrosion rate, indicating the both environments still below the critical relative humidity. For the 73%RH specimens, on the other hand, they presented significantly high corrosion rate, and the major corrosion product was copper(I) oxide (Cu2O).