For your reading pleasure.
http://www.howtosavemoney.ca/which-rust-proofing-service-is-best
Part of the article
What Rust Protection Is Best?
These are the typical choices you have for brand name rust proofing:
Rust Check
Krown
Corrosion Free
Plus, a few other products that you can only apply yourself (not recommended).
There have been several tests run by the Canadian Army on which rust proofing product provides the best protection. You can read the 2006 report here and this post at RedFlagDeals summarizes the results nicely.
The Best Protection
The clear winner in the army tests is Corrosion Free! They found that Corrosion Free was more than 90% effective at inhibiting rust even in the harshest climates. The next closest product was only 70% effective and to my great horror Rust Check was rated at under 40% effective.
That’s what I get for being brand loyal all these years without doing my research! Rust Check definitely works, but I could have been doing so much better all along had I known.
The Best Warranty
The warranty by Rust Check and Krown only covers rust originating from the inside of metal panels and excludes floorboards and sometimes roof panels. They also require an actual hole in the vehicle before they will honour the warranty. Corrosion Free is the only one to cover all body panels and have no restrictions on where the rust originates from. They also don’t necessarily require a full hole before getting it fixed for you. You can read their full warranty sheet here.
Application Interval
Rust Check and Krown require reapplication every 12 months to keep your warranty valid, whereas it is 18 months with Corrosion Free. Less appointments and less hassle, sounds good to me.