Effects of cold work on the corrosion susceptibility of Steam Generator tubing alloy

Abstract: This research is about the effects of the cold work on the corrosion behavior of Steam Generator (SG) tubing alloys. The cold work was introduced to SG tubing by cold-rolling and indentation. The former is used to evaluate the effect of plastic deformation on macro-scale and the latter is to simulate the localized plastic deformation. The cyclic polarization curves indicated that the cold work promoted the active dissolution and increased the passive current densities of alloys in simulated SG crevice chemistries. According to Mott-Shottky measurements, the passive films on the cold-rolled alloys have higher donor densities, implying more defective film structures. The structure of the passive films pre-passivated at 300 °C was investigated by using XRD. The Scanning Kelvin Probe (SKP) tests show that the cold-rolling reduces the work function values. The Scanning Electrochemical Microscope (SECM) results show more evidence that effect of the indentation on the localized corrosion behavior of SG tubing materials in simulated crevice solutions. The possible reasons for the observed changes in corrosion behavior of cold worked alloys are discussed.

Keywords: SG tubing materials; cold work; corrosion; SKP; SECM