Susceptibility to the Absorption of Atomic Hydrogen in API 5L X60 Steels with Unconventional Heat Treatment

The electrochemical behavior of API 5L X60 steel is analyzed in the as-received state and after nonconventional quenching (heated at 1050 degrees C for 30 min and then quenched in water) by the methods of potentiodynamic polarization and electrochemical impedance spectroscopy in a standard NS4 solution. The samples are potentiostatically hydrogenated in the NS4 solution for different times and the concentration of subsurface absorbed hydrogen is evaluated by electrochemical oxidation. The heat treated samples absorb smaller amounts of subsurface hydrogen as compared with the base metal due to the presence of more reversible traps in the bainite and acicular ferrite phases. The kinetics of hydrogen formation is monitored by recording the currents directly related to the surface changes observed in the tested samples. The standard deviation of current in heat-treated steel samples reveals lower values than in the base metal, which indicates the presence of difference in the catalytic activity between the analyzed two types of metallurgical conditions.