The corrosion resistance of green silicon carbide (SiC) and black silicon carbide (SiC) differs slightly due to variations in purity and microstructure, though both are generally highly resistant to chemical attack. Here’s a detailed comparison:
1. Purity & Composition
Green Silicon Carbide (SiC)
Higher purity (≥99% SiC)
Contains minimal metallic impurities (e.g., iron, aluminum)
More uniform crystalline structure
Black Silicon Carbide (SiC)
Lower purity (≥98% SiC)
Contains more impurities (e.g., carbon, silica, and trace metals)
Slightly less uniform structure due to manufacturing differences
2. Corrosion Resistance
Both types are highly resistant to:
Acids (hydrochloric, sulfuric, nitric at moderate temperatures)
Alkalis (better than most ceramics but can slowly degrade in strong bases at high temperatures)
Oxidation (forms a passive SiO₂ layer at high temperatures, protecting the bulk material)
Key Differences:
Green SiC performs slightly better in harsh chemical environments due to fewer impurities, which can act as corrosion initiation sites.
Black SiC may show slightly higher corrosion rates in strongly oxidizing or caustic conditions due to impurities.
3. Temperature & Environmental Stability
Both resist oxidation up to ~1600°C (in air), but green SiC may last longer due to fewer reactive impurities.
In molten metals or salts, black SiC may degrade faster if impurities react.
4. Applications Based on Corrosion Resistance
Green SiC: Preferred for high-purity applications (e.g., semiconductor components, advanced ceramics, corrosive chemical handling).
Black SiC: Used where extreme purity isn’t critical (e.g., abrasives, refractories, general industrial wear parts).