One of the biggest reasons for disappointment or perceived failure is a mismatch between what a user expects their sealant to do (act flexible like silicone) and what the product is designed to do (cure rigidly for a strong, thin bond).
Many hobbyists and DIYers are familiar with RTV (Room Temperature Vulcanizing) silicone gasket makers, which cure into a thick, rubbery, highly flexible material. When they switch to an anaerobic flange sealant, they are often surprised by the cured material’s rigidity, leading to concerns that the seal will crack under vibration or thermal stress.
The key distinction lies in the sealant’s intended environment:
| Feature | Anaerobic Flange Sealant (e.g., Incure) | RTV Silicone Gasket Maker |
| Cured Form | Hard, durable thermoset plastic (can be rigid or semi-flexible) | Soft, highly flexible rubber |
| Gap Fill | Very small, precision gaps (max 0.25 mm) | Large, non-uniform gaps (0.5 mm+) |
| Ideal Flange | Rigid, machined metal-to-metal surfaces | Stamped sheet metal, plastic, or uneven surfaces |
| Cure Trigger | Absence of air + Metal contact | Moisture in the air |
The Anaerobic Advantage: Strength in a Thin Film
The rigid nature of a cured anaerobic sealant is its strength. It locks the joint in place, prevents movement between the flanges (which would otherwise lead to leaks), and withstands high internal pressure.
However, recognizing the need for some give, many modern anaerobic flange sealants are formulated to offer a degree of flexibility—and this is where proper product selection comes in.
Incure HeatGrip™ 504 for Flexible Anaerobic Performance
To bridge the gap between user expectation and anaerobic performance, we recommend Incure HeatGrip™ 504 Flexible General Purpose Gasket Sealant.
The 504 is the ideal choice because it is specifically formulated to provide the best of both worlds:
- Medium Flexibility: Unlike high-strength, rigid anaerobics (like the 503), the 504 cures into a semi-flexible adhesive layer. This cured flexibility allows the seal to effectively manage minor vibrations, thermal expansion,and slight dynamic movements in the joint without cracking.
- Rigid Performance: Despite its flexibility, it still provides the strength of a true anaerobic sealant (5.2 N/mm2) and the benefit of a thin, form-in-place seal that prevents flange movement.
- High Resistance: It maintains this flexible seal up to 150∘C and offers excellent resistance to industrial fluids.
When to Expect Rigidity: If you chose a rigid-curing sealant (like Incure’s 503 high-temp option), a hard cure is normal and desirable for static, high-heat environments.
When to Expect Flexibility: When using the 504, the seal will feel much tougher and more durable than RTV, but the cured polymer offers enough elasticity to survive the stresses of typical automotive and industrial equipment.
Conclusion: If you need a precision seal on a rigid flange that can tolerate some movement, the HeatGrip 504 is the best way to get anaerobic strength with the flexibility you need. If your joint is non-machined or has a large gap, you must use RTV silicone.