• Introduction
• Background
  • History
  • Process Plant
  • Recycling Sealant
• Get the Best
  • Gel Time
  • Sealant Condition
  • Temperature
  • Orientation
  • Casting Condition
  • Vacuum
  • Using Test Rings
  • Test Ring Chart
  • In Conclusion
• Standards
  • Review
  • Proposed Changes
  • MIL-1-1756C
  • Suppliers
• FAQs
• Links
• Contact

Frequently Asked Questions

When should I impregnate?

This depends on where the leakage is; from a cast surface, or from/to a machined face. If the former, it is advisable to impregnate in the as cast condition. Otherwise, it's better to impregnate after machining.

What size of porosity can be sealed?

This is a question everyone asks. Unless you can see through the defect, it is impossible to judge. It's not what you see on the surface that matters, but the formation of the porous channel through the body of the component.

Modern day methacrylate impregnants, due to their low viscosity and the very nature of the impregnation application, used in the process is being unable to seal seriously large defects and especially if structural weakness exists. The best advice is: If in doubt, impregnate it. It is best to allow the process to decide what can and cannot be impregnated.

What types of materials can be sealed with methacrylate sealants?

Thermal cure sealants are not normally affected by different materials such as iron, bronze, aluminium, ceramic, GRP, carbon. In fact any inert material that is porous is impregnatable.

How can I guard against sealant failure?

Know your component – identify where it leaks. Place it in the process basket so that it does not air lock. Regularly check your sealant and most important of all check your cure temperature. The latter is one of the most regular reasons for component failure.

How many times can I impregnate?

Assuming your system is working correctly, one impregnation cycle only should be all that is needed. Twice should be the maximum. With a correctly run system and good quality sealant, it is not usually necessary to impregnate twice. Check your system and quality of component if the latter is common place.

Should I impregnate components cold or warm?

It has been found that it is beneficial to impregnate components warm, but check with your sealant supplier first as some methacrylate sealants are more sensitive than others to increased ambient temperatures.

How long can a methacrylate sealant be used for?

High quality sealants can be used almost indefinitely, dependent on conditions of application. Good housekeeping is important, particularly ensuring that components are clean and dry and free of contamination.

What is the difference between wet and dry vacuum impregnation?

Wet vacuum impregnation is the workload is directly placed into the sealant within the autoclave and a vacuum is pulled through the sealant. When using dry vacuum impregnation the workload is placed into an empty autoclave, the vacuum is achieved first then the sealant is admitted to the autoclave before returning the autoclave to atmospheric pressure.