The effect of dissolved oxygen respectively dissolved hydrogen on corrosion behavior of CuCrZr alloy in high temperature water

In Japan Demonstration fusion reactor, the divertor plays a critical role for it helps sustaining plasma shape and hence demanding high requirements on its structural materials for the cooling system. CuCrZr alloy is considered as one of candidates and would be used in one independent cooling system. Proposals of operating conditions would be similar with fission light water reactor, where experiences have shown that water chemistry significantly influences corrosion behavior. Available references on the corrosion of CuCrZr also address the importance of water chemistries. Because the design proposal could be one of proposals towards reactor, it is worthwhile an investigation to understand the corrosion behavior of CuCrZr alloy under high temperature water environments. This work aims at the effect of dissolved oxygen, and dissolved hydrogen on corrosion behavior. Tests were conducted in an autoclave with relatively static water flow. Three different water chemistries: water with dissolved oxygen 100 ppb, water with dissolved hydrogen 1600 ppb and degassed water were chosen. The exposure time of CuCrZr coupons was 100 hr. Results showed that specimens in water with oxygen 100 ppb had highest weight loss with light-reflecting, grain-oriented surface while in water with hydrogen 1600 ppb had lowest weight loss with tarnished surface and nanoscale pure copper precipitates attached. It is believed that hydrogen reduced dissolved copper ions back to copper atoms; atoms returned to surface in precipitate forms hence reducing weight loss.