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Corrosion testing in 500bar CO2

TWI has designed, built and commissioned a 500bar test facility (Figure 1) which was used for testing of the corrosion performance of carbon steel welds in 500bar CO2 to simulate high-pressure (HP) oil and gas wells.

Industrial Challenge

Handling acidic gases such as carbon dioxide (CO2) and hydrogen sulphide (H2S) is a major technical challenge for the oil and gas sector. In the presence of free water, these gases can cause severe corrosion, and H2S can induce sulphide stress cracking (SSC) and/or hydrogen damage. 

Research on the effects of a high CO2 partial pressure on materials has recently gained interest as the oil and gas industry seeks to explore deeper wells where the temperatures and pressures are higher than in traditional fields. Some of these wells contain a substantial concentration of CO2. At elevated pressure (dependent on the temperature), CO2 can form a supercritical fluid  which complicates the quantitative measurement of corrosion.

Therefore, while the testing of materials in gaseous CO2 in the presence of water is well established, the experimental data on testing in HP CO2 are sparse. New test methods are required for assessing the behaviour of materials such as metals, polymers and metal-polymer systems in contact with HP CO2 environments.

Work programme

To address the current lack of data on HP CO2 testing, TWI’s CO2 test facility was used to assess carbon steel welds at 40°C in a de-aerated 3.5wt% NaCl solution which was purged with 500bar CO2for 30 days.

Examination of cross-section revealed that the specimen was covered with a 20-40µm thick carbonate scale. This scale was identified as siderite, an iron (II) carbonate mineral, by XRD. Some areas also showed a number of large pits of 300-500µm width (Figure 2).

Testing carried out under lower pressure, gaseous CO2 in a similar NaCl solution caused more general corrosion and scaling (Figure 3).

Further tests and analyses are being undertaken at TWI to advance the understanding of the behaviour of materials in HP CO2.

For more information, please email contactus@twi.co.uk

Figure 1: 500bar test facility
Figure 1: 500bar test facility
Figure 2: Micrograph of the cross-section after testing at 500bar
Figure 2: Micrograph of the cross-section after testing at 500bar
Figure 3: Micrograph of the cross-section after testing at 10bar
Figure 3: Micrograph of the cross-section after testing at 10bar
Avatar Dr Shiladitya Paul Research & Product Development Programme Manager, Surface, Corrosion and Interface Engineering

Shiladitya joined TWI in 2008 after a PhD in Materials Science and Metallurgy from the University of Cambridge, UK, and subsequently became the Director of MatIC in January 2018. He is an innovative technology specialist with experience in the industrial development and application of specialised materials, coatings, and corrosion mitigation methods. He has published over 100 papers/articles on materials, coatings and corrosion. Shiladitya is active in the scientific community as a peer reviewer and member of the editorial team for several journals, and on a number of international, scientific and industrial committees, including holding the positions of Vice Chair of the European Federation of Corrosion (WP9), Chair of the 2023/24 symposium on Thermal and Cold Spray Coatings at AMPP Annual Conference, and a member, and judge, of the Journal of Thermal Spray Technology (JTST), Best Paper Award committee. He is a registered Chartered Engineer (CEng) in the UK, and a Fellow of the Institute of Materials, Minerals and Mining (FIMMM). 

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