Case Study: Why a Chemical Processing Plant Switched from RB-SiC to SSiC
A chemical processing facility operating in an acidic environment was using components made from Reaction Bonded Silicon Carbide (RB-SiC) for pump seals and corrosion-resistant structural parts. The system was exposed to concentrated sulfuric acid (H₂SO₄) at elevated temperatures around 100°C.
After several months of operation, the plant observed gradual performance degradation, including surface erosion and dimensional changes in certain RB-SiC components.
To improve service life and operational stability, the engineering team evaluated Pressureless Sintered Silicon Carbide (SSiC) as an alternative material.
Material analysis showed that the reaction bonded silicon carbide (RB-SiC) components contained approximately 10–15% free silicon phase.
In strong acid environments, this residual silicon can undergo selective corrosion, gradually weakening the material structure and reducing long-term reliability.
As a result, the material structure gradually weakens, leading to:
- Surface corrosion
- Reduced mechanical strength
- Increased maintenance frequency
- Shorter component lifetime
Testing data under sulfuric acid conditions showed a significant difference in corrosion rate:
- SSiC: 1.8 mg/cm²·yr
- RB-SiC: 55.0 mg/cm²·yr
This difference became critical in long-term continuous operation.
The facility replaced several RB-SiC parts with pressureless sintered silicon carbide (SSiC) components manufactured with high densification control.
Key material characteristics included:
- density ≥ 3.05 g/cm³,
- near-zero open porosity,
- no free silicon phase,
- flexural strength ≥ 380 MPa,
- and stable high-temperature performance.
After switching to SSiC components, the plant observed several improvements:
- Improved corrosion resistance
The absence of free silicon significantly reduced acid attack. - Longer service life
Component replacement intervals increased noticeably. - More stable operation
Dimensional stability under thermal and chemical stress improved. - Reduced maintenance downtime
Lower corrosion rates led to fewer shutdowns for part replacement.
The key difference between SSiC ceramic materials and reaction bonded silicon carbide (RB-SiC) systems lies in the presence of free silicon.
RB-SiC contains residual silicon formed during reaction infiltration, while SSiC forms a dense, fully sintered SiC structure without a secondary silicon phase.
In strongly corrosive environments, especially acids, the silicon phase in RB-SiC becomes the weak point of the material.
This makes SSiC a more suitable choice for:
- Chemical processing equipment
- Corrosion-resistant pump components
- High-temperature acid environments
When selecting between SSiC and Reaction Bonded SiC, the operating environment plays a critical role.
For applications involving:
- High temperature (>1200°C)
- Strong acids or corrosive chemicals
- Long-term structural stability requirements
SSiC typically provides better long-term performance.
RB-SiC remains a viable solution for applications where cost efficiency is a priority and the operating environment is less aggressive.
Pressureless sintered silicon carbide (SSiC) components are widely used in:
- chemical processing systems,
- corrosion-resistant pump components,
- seal rings,
- and high-temperature acidic environments.
Key advantages include:
- excellent acid resistance,
- no free silicon phase,
- low porosity,
- and long-term structural stability.
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