Effect of Polyacrylic Acid on Flow Accelerated Corrosion Behavior of Pipe Materials in Secondary Circuit of Nuclear Power Plant

Using nuclear power plant secondary circuit material evaluation test platform to simulate the environment of secondary circuit in power plant, the flow accelerated corrosion (FAC) rates of pipe materials with different Cr content were studied under high-purity polyacrylic acid (PAA) dispersant condition. And the morphology of oxide films on surfaces of pipe materials after FAC was observed by scanning electron microscopy (SEM). The results showed that under the conditions of 150℃, pH (25℃) 9.2, flow rate of 5 m/s, and dissolved oxygen content less than 10 μg/L, continuous circulation for 200 h, adding 1 mg/L PAA did not accelerate the FAC rates of alloy steels WB36 CN1, A106B with low Cr content, but accelerated the FAC rate of alloy steel A335 P22 with high Cr content from 0.005 1 mm/a to 0.007 8 mm/a. PAA made the oxide film on the surface of alloy steel A335 P22 loose and porous by promoting the dispersion of small loose oxide particles and slowing down the deposition of particles. If the dosage of PAA in feed water is no more than 5 μg/L, the risk of service life reduction of the secondary circuit pipe caused by long-term online PAA application should be low.