CO2 corrosion behavior of high-strength martensitic steel for marine riser exposed to CO2-saturated salt solution

Abstract

CO _2 corrosion is an inevitable problem of marine riser steel for oil and gas transportation. In the following work, the corrosion behavior was revealed in terms of microstructure characterization, corrosion kinetic curves, morphology and phase composition analysis of corrosion products, distribution characteristics of elements in corrosion products and electrochemical corrosion behavior. The results showed that FeCO _3 crystals gradually evolved from dispersed clusters to complete FeCO _3 layers with the extension of exposure time, which improved the protection ability of the corrosion product layer to the substrate. With the prolongation of corrosion time, the protective effect of the corrosion product layer on the substrate was gradually enhanced. The self-corrosion potential moved to the positive direction and the self-corrosion current density decreased. As a result, the corrosion rate gradually decreased and tended to be stable. The increase of corrosion-resistant elements content made the self-corrosion current density significantly decreased. The high content of corrosion-resistant elements effectively hindered the contact of corrosive ions with the substrate and inhibited the electrochemical corrosion reaction.

Keywords

• CO2 corrosion
• high-strength steel
• tempered martensite
• marine riser