DIY: Rust Protection Test

I’ve wanted to buy a new car for a couple years, and last winter’s debacle with my 2002 Sentra’s head gasket being blown out of commission only reaffirmed my decision to impulse-buy a new car. After some disappointing market research, I settled on a 2014 Mazda 3 Hatch, the only car in my price range that felt premium and well-made. Now that I’ve driven it for a year, it’s probably time to write up a nice review, because I love the car aside from a few design quirks here and there. 

Living in New England, we get a ton of salt sprayed all over our cars for 3-4 months out of the year. And no matter how advanced the modern metal coating technology, certain car parts like the exhaust will always take a hit from being constantly covered in moist salt. 

Sure, everything will eventually rust out on any car in any climate, but I wasn’t about to let my one year old Eve start to rust. Short of spraying the entire undercarriage with industrial-grade rust-protection, I wanted to find out, which conventional, non-invasive treatments work best at repelling water and salt. 

The corrosion inhibitors I’ve put to the test:

  1. WD-40 Specialist Long-Term Corrosion Inhibitor
  2. CRC Food Grade Silicone Mold Release
  3. CRC Heavy Duty Silicone
  4. Liquid Wrench White Lithium Grease

To facilitate the corrosion test, I’ve divided a used rotor that I just took off my Sentra into 4 sections by masking tape, each section to test one of the products above. Then I carefully applied the four products to the rotor.

Over the course of the week I sprinkled the rotor with some tap water and added some salt periodically to simulate winter driving conditions. 

I was expecting the results to be somewhat varied, but after a week of spraying the rotor, there was only one product that stood up to the test - WD-40 Long-Term Corrosion Inhibitor. 

Both the silicone sprays failed within a day, as rust started to creep in, and the white lithium grease took a little longer, 3-4 days to start showing signs of rust.

Untreated side

Untreated side

Treated side (numbers correspond to inhibitors listed above)

Treated side (numbers correspond to inhibitors listed above)

The section treated with WD-40 maintained a clean metal finish with practically no rust.