Hydrazine-Dependency of Low-Alloy Steel Flow-Accelerated Corrosion in a Deoxygenated Solution at 250°C
In the nuclear power plants (NPPs), wall thinning of the piping materials is generally caused by a flow-accelerated corrosion (FAC) and leads to a rupture with no warning unless it is detected and repaired in a timely manner. To reduce the FAC, it is better to use low-alloy steels, such as 1Cr-½Mo and 2¼Cr-1Mo, having higher FAC-resistance than carbon steel. Meanwhile, in the secondary water chemistry at the NPPs in Korea, hydrazine concentration is maintained within the range of 100~150 ppb. For applying these low-alloys to a piping material, we investigated the influence of hydrazine concentration on their FAC. An experiment was carried out at pH25°C of 9 controlled with ammonia in a deoxygenated aqueous solution containing 0~250 ppb-hydrazine by using a FAC test loop at 250°C for 300 hours. Experimental weight loss showed a hydrazine concentration dependency of the FAC in this concentration range, giving minimum at 150 ppb.
Young Won Chang, Nack J. Kim and Chong Soo Lee
K. W. Sung et al., "Hydrazine-Dependency of Low-Alloy Steel Flow-Accelerated Corrosion in a Deoxygenated Solution at 250°C", Advanced Materials Research, Vols. 26-28, pp. 1133-1136, 2007