We often write about the different types of vacuum impregnation systems that are commonly used and how each may be best suited for use when processing a particular type of part. Once you have determined the type of system that is required, you then need to select the appropriate sealant for the system and application.
Listed below are advantages and disadvantages of each sealant and which system would be best suited for its application.
Thermal Cure Sealant
Anaerobic Sealant
Application
Typically used for sealing micro porosity in castings.
Can be used for powder metal component but not the best application due to washout.
Typically used for sealing through porosity in powder metal components.
Wires or over molded components with dissimilar material.
Can be used for castings but not the best application.
Advantages
Fast curing (3 – 6 minutes) allowing parts to be pressure tested in continuous flow or transfer line type application.
High recoverable rate of sealant due to use of centrifuge.
Cures at room temperature making it ideal for use with wires and over molded components with dissimilar material that have varying degree of thermal expansion.
Disadvantages
Requires heat to initiate crosslinking process.
Castings can discolor or oxidize in water during the curing process without the use of a suitable corrosion inhibitor.
Can require 12 hours to fully crosslink.
Must maintain refrigeration and aeration system.
System Type
DVP – Best suited.
WVP – Better suited.
WV – Good method depending on application.
WV – Best suited
WVP – Better suited depending on application.
DVP – Can be used depending on application and system type. Note – Not recommended for conventional DVP systems that rely on the transfer of sealant.
Within both these main categories of sealant are specialty applications:
Resistance to E85 fuel and B20 Bio-diesel.
Fully flexible sealants that are capable of retaining their cured properties even when wrapped around a mandrel five times the diameter of the wire.
Flame retardant application for the aerospace industry.
WQA/NSF and UL approved for drinking water systems.
In conclusion, this article is a general overview of the types of sealant that are available today.
