CO2 corrosion behavior of 1% Cr-13% Cr steel in relation to Cr content changes

The corrosion behavior of 1% Cr, 3% Cr, 4% Cr, 5% Cr, 6.5% Cr, 10% Cr and 13% Cr steel samples were investigated in a simulated oil field environment (60 degrees C, 2 m s(-1), 2 MPa CO2). Weight loss tests were conducted in a high-temperature and high-pressure autoclave for 120 h. Scanning electron microscopy and energy dispersive spectroscopy were used to study the morphology and composition of corrosion scales. Polarization curves of the aforementioned seven steel samples were studied as well. The results showed that the average corrosion rates decreased with increasing Cr content in the steel substrate. The 1% Cr steel sample underwent mesa corrosion, and 10% Cr and 13% Cr steel showed very low corrosion rates owing to passivation. In the cases of 3% Cr-6.5% Cr steel, the Cr content was inadequate for passivation, but these samples showed low corrosion rates owing to the protective effects of corrosion scales.