The CCUS Corrosion Paradox: Defining the Limits of Steel
As the global energy sector pivots toward Carbon Capture, Utilization, and Storage (CCUS), the metallurgical conversation often focuses erroneously on long-distance transport pipelines. While standard Carbon Steel or API 5L X65 suffices for dry, pure CO2 transport, the reality at the capture and injection sites is far more aggressive. At our manufacturing facilities, we recognize that the critical failure points in CCUS infrastructure are not the pipelines, but the heat exchangers, compressors, and injection well components handling impure streams.
When CO2 capture streams contain impurities such as SOx, NOx, or free water, the thermodynamic environment shifts drastically. The formation of carbonic acid, combined with sulfuric or nitric acids from flue gas impurities, creates a pH environment that rapidly degrades standard 13Cr and even Super Duplex stainless steels. In these specific "unmanageable" corrosion environments, Titanium is not merely an option—it is a requisite for operational integrity.
Handling Impure Wet CO2: The Case for Grade 12 and Grade 2
The aggressive nature of wet CO2 containing chlorides and sulfur species demands a material with a stable passive oxide layer. Titanium’s naturally forming TiO2 film provides immunity to general corrosion and pitting where ferrous alloys fail.
Material Selection: For lower temperature processing units and heat exchangers, ASTM B338 Grade 2(Commercially Pure) remains the volume standard. However, for injection environments involving higher temperatures and sour interactions, we are shifting production focus to Grade 12 (Ti-0.3Mo-0.8Ni).
NACE Compliance: Following recent revisions to NACE MR0175 / ISO 15156, Grade 12 has seen relaxed restrictions, allowing its application in sour service environments without previous hardness caps. Our mill now qualifies UNS R55400 for high-pressure applications, ensuring compliance up to 41 HRC.
Supercritical CO2 (sCO2) Power Cycles
Beyond capture, the efficiency of sCO2 power cycles relies on handling fluids at supercritical states where density resembles liquid but viscosity resembles gas. This creates unique erosion-corrosion challenges. We manufacture ASTM B861 Seamless Pipe specifically for these high-velocity loops. Unlike 13Cr, which requires strict velocity limits to maintain passivation, Titanium withstands the high turbulence of sCO2 cycles without film degradation.
Comparative Analysis: Material Suitability in CCUS Streams
Environment
Carbon Steel (X65)
Super 13Cr / Duplex
Titanium (Gr. 2 / Gr. 12)
Dry CO2 Transport
Recommended (Cost Effective)
Over-specified
Commercially Non-Viable
Wet CO2 (Pure)
Severe Corrosion Rate
Suitable
Excellent
Wet CO2 + SOx/NOx
Rapid Failure
High Pitting/SCC Risk
Recommended
sCO2 High Velocity
Erosion Risk
Velocity Limits Apply
High Erosion Resistance
Manufacturing Capability: Vertical Integration
Supply chain security is currently the primary risk factor for global EPCs. Unlike Western mills reliant on imported sponge, our production is vertically integrated within the Chinese titanium ecosystem, which now accounts for approximately 70% of global sponge production. This allows us to guarantee raw material purity and delivery timelines.
We are currently producing seamless Titanium pipe up to 330mm OD and EFW welded pipe up to 5,000mm OD. For critical CCUS projects, we recommend early engagement with our technical metallurgy department to define specifications that balance the high initial CAPEX of titanium against the catastrophic OPEX costs of material failure in impure CO2 streams.
