In the vacuum impregnation industry one of the more frequent topics of discussion surrounds the difference between anaerobic and thermal curing impregnation sealants.
It is well known that thermal cure sealants, like Godfrey & Wing’s 95-1000A and 95-1000AA, are more widely used than anaerobic sealants (95-1000AC and ACP). Many will say the reasons for the increased use of thermal cure sealants are acquisition cost of the sealant or equipment. Others will cite ease of maintenance while still others will say it is due to the elimination of a host of failure modes.
In reality the decision for choosing a specific style of sealant lies with the part to be impregnated. Some parts are just more likely to be sealed in one versus the other. It has nothing to do with the quality of the sealant, but it has everything to do with the materials being impregnated and the size of the pore or leak path.
Compare Vacuum Impregnation Sealanats
| Thermal Cure | Anaerobic | |
|---|---|---|
| Curing | Polymerizes when heated to 195°F | Polymerizes in the absence of air over 24-48 hours |
| Pressure Testing | Immediately after impregnation | Need to wait 24-48 hours after impregnation |
| Maintenance | Continuous refrigeration | Continuous refrigeration and aeration |
| Packaging | 5 gallon, 50 gallon, 250 gallon | 4-5 gallon carboy |
| Applications | Castings, aluminum, iron, steel, zinc | Powdered metal, electrical applications, cables |
Powdered metal applications have large, through porosity and work best when using an anaerobic sealant. Why is this? First, once impregnated into the part, the sealant may be activated in a chemical bath to seal the pore at the surface, allowing the remaining sealant trapped in the porosity to cure over time. This reduces the chance of sealant migration from the pore which could be found when using a thermal curing sealant with large open porosity.
Likewise when sealing micro-porosity in a casting, a thermal cure sealant will perform better than an anaerobic as the process used to impregnate thermal cure sealants is more robust and thorough. Also since the sealant is forced to cure when it reaches the 195°F cure temperature, impregnated parts may be tested immediately after impregnation. Thermal cure sealants also will be less reactive and have a much longer pot life than anaerobic sealants.
