Corrosion Behavior of Oil Casing Steel under Combustion Drive Oil Condition at Different Temperatures

The corrosion behavior of oil casing steels N80, BG80-3Cr, P110, BG90H, BG90H-9Cr and BG90H-13Cr at different temperatures was investigated under simulated combustion drive oil condition, and the corrosion mechanism was analyzed. The results show that at a relatively low temperature (50℃), oxygen and CO₂ corrosion mainly occurred in the tested steels. The corrosion product was FeCO₃ and had poor protection poerformance. Therefore the average corrosion rate was relatively high. At a relatively high temperature (150℃), oxygen corrosion gradually took the dominant role. The corrosion products consisted of Fe₃O₄ and FeCO₃, whose protection performance decreased, and the average corrosion rate increased. At a high temperature (250℃), the corrosion mechanism was oxygen corrosion. The corrosion product was Fe₃O₄. The Fe₃O₄ hydrate film had high protection performance, and uniform corrosion rate decreased. The average corrosion rates of N80 steel, BG80-3Cr steel, P110 steel, BG90H steel were significantly higher than those of BG90H-9Cr steel and BG90H-13Cr steel, and were all higher than 0.2 mm·a^-1 at 50,150℃. The average corrosion rates of BG90H-9Cr steel and BG90H-13Cr steel were both lower than 0.2 mm·a^-1, indicating good corrosion resistance under combustion drive oil condition.