Comparative analysis of stainless steels used for oil production in deep water

Since the discovery of the first petroleum off-shore fields 30 meters below sea level in the Brazilian northeastern coast in 1968, the development of new technology for oil extraction and production in deep water has led to the achievement of oil extraction in increasing deepness until outstanding levels such as 1800 meters have been attained in 1999-2000. In the present work, a study is carried out, which simulates the conditions of operation and exploration of petroleum in a marine platform for evaluating corrosion resistance and mechanical properties of duplex and (12% chromium) martensitic stainless steels, through the determination of uniform corrosion rate, local corrosion resistance, stress corrosion cracking resistance and cyclic slow strain rate tests. Tensile and hardness tests were also performed as well as microstructural and automatic image analysis. Results show that duplex and superduplex stainless steels were approved in all types of test conditions and presented the best combination of mechanical properties, whereas martensitic 12% Cr steel failed in some conditions. Howeveer, dut to their lower cost the martensitic stainless steels must be considered for this use.