Corrosion immersion tests of 3%Cr steel and API X65 pipeline steel were carried out in the
high-pressure high-temperature autoclave, in order to simulate the typical corrosion environment of
oil and gas transported pipeline. The effects of temperature and CO2 partial pressure on corrosion
behaviors were investigated, and the purpose of this paper was to compare the corrosion resistance
of 3%Cr steel with API X65 pipeline steels in CO2 corrosion environment.
The results show that, the corrosion of both 3%Cr steel and API X65 pipeline steel were slight in
mild corrosion environment, so we could choose API X65 steel in these environment. With
temperature or CO2 partial pressure increasing, the corrosion resistance of 3%Cr steel was superior
to API X65 pipeline steel. The analysis of composition and morphology revealed that the corrosion
product film of 3%Cr steel was composed of FeCO3, Cr(OH)3 and Cr2O3. An amorphous scale
without grain boundaries and pores was formed on the surface of 3%Cr steel due to the Cr element
enrichment, which offered considerable resistance to corrosive medium, therefore the corrosion rate
was decreased and local corrosion was inhibited.
Keywords: 3%Cr steel, API X65 pipeline steel, temperature, CO2 partial pressure, corrosion rate,
corrosion product film