Is the Chassis Black Finish Coating a rust sealer?

While it does have rust sealing properties, it is not nearly as good of a rust sealer as Mastercoat Permanent Rust Sealer, and this is why we use it as a topcoat for the rust sealer. Chassis Black only has resin, which blocks moisture only. Permanent Rust Sealer has aluminum to block the oxygen and resin to block the moisture, creating an airtight seal.