Which of the following actions is critical as part of the surface preparation before sealing?

Preparing surfaces before sealing is crucial for ensuring strong adhesion and the longevity of the seal. Applying a primer helps create a suitable surface that enhances the bond between the sealant and the base material. Primers are designed to improve the adhesion properties and may also serve as a barrier against contaminants that could weaken the seal.

Cleaning with solvents is equally important as it removes any grease, dirt, or other contaminants that could interfere with adhesion. Solvents ensure that the surface is free from any substances that would compromise the bond of the sealant.

Both steps are vital because they work together to ensure that the surface is not only clean but also optimized for the sealant application. The combination of cleaning and priming provides the best possible surface for sealing, ensuring a durable and effective seal. Thus, the action of both applying a primer and cleaning with solvents is critical in the surface preparation process before sealing.