In many cases there are applications that require protection against the creation of corrosion/ penetration of various liquids and/or gases.
The outstanding advantage of the parylene coating is its excellent protection against the penetration of liquids and moisture. In fact, no acid/ gas/ base can harm the coating or, alternatively, remove the coating.

The molecular structure of parylene C as observed with x-rays is tricyclic. However, when a longitudinal section is made of parylene, it can be seen that parylene has a lamellar structure resembling dense fish scales that effectively prevent the penetration of liquids, gases or acids.

Impermeability data for parylene regarding various gases and water, compared to other conformal coatings.