Experimental Study on Corrosion Characteristics of CO2 Pipeline for Offshore Transport and Geological Storage

Abstract

Among the technologies, CCS (Carbon dioxide capture and storage) technology is assumed and arising as crucial technology for reducing anthropogenic carbon dioxide and bridging to hydrogen economy. CCS technology includes carbon dioxide capture on the large point source, transport of captured carbon dioxide stream and storage of carbon into safe geological formations. Among the CCS processes, capture side is developing with many demonstration projects, focusing on the efficiency improvement of wet and dry absorbents, material improvement for membrane, construction cost down, etc. But in transport side, the technology is in the initial stage. In Korea, site surveys are mainly focused and operated on the offshore saline aquifers in the east sea of Korea and rather few surveys are processed in the on land side. For the offshore carbon dioxide geological storage, there are two options for transportation, using pipeline or ship. To utilize the offshore pipeline it is possible to use high chrome steel alloy to response to seawater corrosion, though the cost for construction might take huge budget for installation mainly cause of material cost. Otherwise, we considered it might be possible to apply the anti-corrosion coating outside of the carbon steel pipeline to mitigate seawater corrosion and to reduce the cost, so to secure steady and robust operation of offshore carbon dioxide transportation with little concern of corrosion issue. In this study, we investigated the possibility of using carbon steel pipeline with internal phosphate coating and external thermal spray coating as candidate for the offshore carbon dioxide transportation pipeline material. The base material for this study is carbon steel. The pipe internal corrosion test was conducted with fluids of CO2 mixture with additives of water and SO2 gas, and the external corrosion was carried out with 3.5%w NaCl solution. In the case of internal corrosion, all the specimens resulted in corroded surface with rust covered when SO2 was injected over 175 ppmv. In the case of external corrosion, zinc thermal spray with epoxy coating showed that more epoxy sealer is remained than aluminum thermal spray coating. The test result will be used to figure out economically efficient and safe candidate pipeline material.