Assessment of pH and temperature effects on stress corrosion cracking of 1018 low carbon steel

Abstract

Stress corrosion cracking tests (SCC) were performed on 1018 low carbon steel into 0·5M NaCl solution at different pH values and temperatures of 25, 50 and 70°C using the slow strain rate testing technique. Evaluations were complemented with hydrogen permeation measurements and electrochemical impedance spectroscopy. Studies show hydrogen diffusion effects depending on temperature and pH. The maximum hydrogen diffusion was observed at 70°C (pH<1). The SCC susceptibility was measured as the percentage reduction in area and the time to failure and was maximal at pH<1 at the temperatures studied. The most likely mechanism for the cracking susceptibility of 1018 steel in the chloride solutions seems to be hydrogen assisted anodic dissolution assisted by hydrogen embrittlement. After failure, the fracture surfaces were observed by scanning electron microscopy and chemical analysis was obtained by X‐ray energy dispersive spectroscopy. The specimens tested in air exhibited a ductile type of failure, whereas, in the corrosive solution the specimens showed a brittle fracture.

Keywords:

• Stress corrosion cracking
• Slow strain rate test
• Hydrogen embrittlement
• Hydrogen diffusion
• 1018 steel