Effects of scratching on corrosion and stress corrosion cracking of Alloy 690TT at 58 °C and 330 °C

Scratched Alloy 690TT were characterized using X-ray stress analysis technique, nano-indentation, SEM, electrochemical and immersion tests. The stresses adjacent to the scratches, which resulted from scratching, were tensile parallel to the scratches and compressive perpendicular to the scratches. In the acidic sodium chloride solution at 58 °C, scratching caused Ecorr to shift negatively owing to a transient anodic current accompanied by a larger difference between Ecorr and the potential of zero charge. At 330 °C in the lead-containing caustic solutions, SCC initiated at the scratch-banks and scratch-beds after 30 days’ immersion. Scratched Alloy 690TT exhibited both IGSCC and TGSCC in initiation.