Abstract
The corrosion behavior of API 2H grade 50 and API 4F steels after 1 h and 24 h of their exposure in freely aerated stagnant 4.0 wt.% NaCl solution was reported. This study was conducted using various electrochemical and microscopic investigations including cyclic polarization, chronoamperometric current-time at an active anodic potential (–0.45 V vs. Ag/AgCl) and the nontraditional impedance spectroscopy tests. It was found that the API 2H and API 4F steels suffer both general and pitting corrosion in the employed chloride solution. Prolonging the exposure time from 1 h to 24 h of the electrodes immersion decreased the pitting corrosion for the investigated steels. The surface morphology performed using scanning electron microscopy indicated that both 2H and 4F steels develop a thick layer of the corrosion product that is responsible for decreasing their dissolution with increasing time. Results obtained from the different techniques were in good agreement with each other and confirmed clearly that the corrosion resistance of the API 2H steel is slightly better than the API 4F steel and this fact increased with prolonging the immersion time of the steels in the electrolytic chloride solution before the measurements were carried out.