Environmental effect on corrosion behavior of 9MnSi5 steel pipelines

Abstract

The increase in the corrosiveness of the produced fluid forces to reconsider the attitude towards the assessment of the serviceability and reliability of oil pipes, paying attention to the problems of increasing their corrosion resistance. The paper analyses environmental impact on pipeline made of 9MnSi5 steel after 12 months of operation in the oilfield to assess the residual life of pipeline and determine safe operating conditions. It was found that corrosion damage developed according to the mechanisms of general, pitting corrosion and stress corrosion cracking. Metallographic study has shown cracks of stress corrosion cracking that developed in environments containing carbon dioxide and hydrogen sulfide. Accelerated method of stress corrosion cracking resistance testing was implemented that allows to understand the tendency of steel to this type of cracking and gives a conclusion about the danger of brittle fracture of the pipeline.