Corrosion behavior of low alloy steels in a CO₂-O₂-H₂S-SO₂ wet gas environment of crude oil tanks

Wet gas corrosion experiments of three low alloy steels containing different contents of elements Ni and Cu were conducted by homemade equipment simulating the oil tanker corrosion environment. The corrosion rate, corrosion morphologies and corrosion products of the three steels in a CO₂-02-H₂S-SO₂ wet gas environment of crude oil tanks were compared and the corrosion mechanism was also analyzed and discussed. The results show that the corrosion morphologies of the three steels are all uniform corrosion; as the corrosion products forming and spalling, the corrosion rate of the steels fluctuates with the increase of testing time. Elements Ni and Cu can obviously improve the corrosion resistance of the steels to the wet gas environment. In the wet gas environment, hydrogen evolution corrosion and oxygen absorption corrosion caused by CO₂-02-H₂S-SO₂ corrosion gases exist as well as wet sulfur corrosion from the oxidation of H₂S by 02. The correlation between wet gas corrosion depth loss DL_t and corrosion time t is properly accordant with the expo-nential relationship DL_t=At⁸, and the values of coefficient A and exponent B of the three steels with different alloy elements were obtained.