Cosmoline RP-342 Heavy Rust Preventative Spray, 3-Pack

Last updated date: June 18, 2021

DWYM Score

9.1

Cosmoline RP-342 Heavy Rust Preventative Spray, 3-Pack

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We looked at the top Rust Prevention Sprays For Cars and dug through the reviews from some of the most popular review sites. Through this analysis, we've determined the best Rust Prevention Spray For Cars you should buy.

Update as June 14, 2021:
Checkout The Best Rust Prevention Sprays For Cars for a detailed review of all the top rust prevention sprays for cars.

Overall Take

This reliable rust prevention spray has been used by the U.S. Armed Forces, commercial companies and consumers since World War II. This newer formula dries faster and last longer than ever, and the coating will never crack, wash off, run off or blister.


In our analysis, the Cosmoline Cosmoline RP-342 Heavy Rust Preventative Spray, 3-Pack placed 4th when we looked at the top 6 products in the category. For the full ranking, see below.

From The Manufacturer

OUR STRONGEST, LONGEST-LASTING & FASTEST-DRYING Rust Preventive Aerosol, PERIOD! 1-coat can reliably protect any metal, steel, or iron surface (parts, equipment, tools, machinery, etc.) for Years!.....indoors or outdoors. DURABLE & TOUGH. Will not crack, craze, blister, run or “wash off”. RP-342 produces a dry-to-the-touch (non-tacky), amber, translucent (see-through) petroleum wax coating that stands up to long-term salt spray, extreme temperatures and other harsh environments. EASY-TO-APPLY: Just spray onto a dry surface, dries in about 25 minutes; You’re Done! TRUSTED SINCE WWII. Has been widely used & trusted by the U.S. Armed Forces, government agencies, commercial companies, and DIYers/consumers for generations. 1,000s of APPLICATIONS across commercial and private industries. Vehicle undercoating is one of the most popular applications. Easily stands up to road salt, chemicals, road debris and won’t wash off like many other undercoating products. One application/coating can protect for years.

An Overview On Rust Prevention Sprays For Cars

Nothing ruins a car faster than rust. Once you find it, the problem can be too far gone to repair. Though auto manufacturers use modern materials and test and treat them, vehicles are still vulnerable to rust.

There are three main types of rust prevention car sprays: tar-based, drip oil and dripless. Tar-based sprays, also known as undercoating, are sprayed onto the exposed parts in the car’s underbody, and in wheel wells and floor pans. These form strong shields, but they can crack.

Drip oil sprays are applied through holes that are first drilled into the vehicle’s body. This is the most common kind of car rust-proofing, but it needs to be done once a year.

The third type, dripless oil sprays, are more similar to tar-based ones. These also harden after you spray them on. As with drip sprays, though, holes still need to be drilled in the vehicle before applying.

Car owners can pay for rust prevention services when purchasing their vehicles. This may already be included in the initial purchase cost. Rust proofing can also be done at a body shop, and can cost anywhere from $125 to $150. Another option is to buy the spray and do it yourself. Most can make wide or narrow sprays, because they come with interchangeable nozzles. Some leave sticky films, while others dry faster, but all are cheaper than taking a car to the shop.

Rust conversion sprays are different, and are used on existing rust. These aerosol sprays convert rust into black coatings, which can then be primed and painted with oil-based top coats. Read the instructions carefully, as you may also have to sand the finish after the spray is applied.

The Rust Prevention Spray For Cars Buying Guide

  • Since tar-based sprays can crack, the vehicles should be inspected at least once a year.
  • Drip oil sprays can be messy, so you may not want to apply them when the vehicle is in the driveway, otherwise you may see oil stains.
  • If using rust converter spray, first remove the loose rust with a wire brush. You don’t want to paint over that.