Cosmoline RP-342 is a specialized version of the classic Cosmoline rust preventive compound; a waxy, petroleum based coating designed to provide exceptional protection against rust and corrosion. Known for its durability and foothold in military applications, RP-342 creates a robust, long-lasting barrier that prevents moisture, salt, and other corrosive elements from reaching metal surfaces. It is widely used in industrial, automotive, military, and marine applications to protect machinery, equipment, and vehicles from rust.

The protective film formed by Cosmoline RP-342 remains soft and pliable, ensuring long-term protection that doesn’t crack, peel, or wash away easily. This durability makes it ideal for protecting undercarriages, machinery, and metal components over extended periods in harsh environments.

Yes, Cosmoline is safe for use on all metal components of your vehicle's undercarriage. It is a non-rubberized/asphalt product, so it will not trap and seal moisture underneath. It adheres well to imperfect surfaces and does not crack, peel, or flake over time; it remains slightly flexible due to its waxy nature, accommodating the natural movements of your vehicle.

Unlike coatings that completely harden over time, Cosmoline RP-342 maintains a tacky consistency that allows it to self-heal minor abrasions. This feature helps maintain a continuous protective barrier even in high-impact areas.

Cosmoline RP-342 is designed to meet stringent military testing standards, including MIL-PRF-16173, Grade 4 and MIL-C-83933., which certifies its effectiveness for long-term rust and corrosion prevention. This makes it a trusted choice for military, government and industrial applications where performance is critical.

Cosmoline RP-342 is best suited for vehicles that are clean, dry, and free of rust. Here’s why:

• Maximum Bonding: It adheres best to bare or primed metal with no corrosion. New vehicles offer the cleanest surface for long-term performance.

• Dry Hard Shell: Cosmoline forms a fast-drying, durable wax coating. On rusted or flaky surfaces, it can lift or fail to seal properly.

• No Creep Action: Unlike products like Woolwax® or Creep N’ Crawl, Cosmoline doesn’t migrate into seams or hidden areas. It needs a clean surface to be fully effective.

• Long-Term Protection: It’s designed as a one-time application for new vehicles, offering multi-year rust prevention with little need for touch-up.

If your vehicle has any rust, we recommend flexible, penetrating coatings like Woolwax for better adhesion, coverage, and durability.

Yes, Cosmoline can be removed with common petroleum-based solvents like mineral spirits.

No - the coating is lightweight and doesn’t significantly affect the weight or performance of your vehicle.