Waxoyl / Rust Proofing

[MartinK]

Hi

Anyone had any experience of applying additional rust-proofing measures to their Volvo?

I tend to keep my vehicles for a (relatively) long time. My last vehicle (Land Rover Discovery) I still have after 7 years & 152000 miles.

I applied additional rust-proofing to my last car, and it really paid off after a few years (brake pipes lasting much longer than normal, minimal underbody rust etc etc).

Scottish roads tend to be heavily salted between November and April, and this wrecks underbody fittings such as untreated brackets, fastenings and brake pipes...

Any advice?

[Mighty Quinn]

Hi

Anyone had any experience of applying additional rust-proofing measures to their Volvo?


No, however, as an engineer who practices metallurgy and electrochemistry on a daily basis, I have a fair amount of experience dealing with corrosion problems.

A protective coating applied to a painted surface under the vehicle may indeed help protect against rust because it is preventing chips and scratches on the paint. However, on unpainted metal surfaces the spray-on rust proofing may actually accelerate corrosion. There are two reasons for this. First, none of the "rust-proofing" systems are waterproof. Moisture and dissolved salt will diffuse through the coating, initiating corrosion at the interface between the coating and the metal. The problem is that you cannot see this corrosion because of the rust-proof coating. Once corrosion initiates at this interface, the coating delaminates slightly and moisture wicks in between the coating and the metal surface, so the area is constantly wet and corroding.

The second reason that rust-proofing can actually accelerate corrosion on non-painted surfaces is that there are almost always areas that do not get coated. If the application of the coating is not of high quality and uncoated regions are present (typically areas that are out of sight), the corrosion rate of these small, uncoated areas may actually be accelerated.

Without a rust-proofing application, most of the underbody will experience some amount of general corrosion or surface rust. This rust is not very deep and isn't too serious. But with a rust-proofing application, you risk getting isolated areas of accelerated corrosion that can result in a significant amount of metal loss and lead to significant problems. However, you may never know this and think that the underbody of your car looks rust-free because these severely corroded areas are difficult to see or find.

Another thing to consider is that Volvo has a 12 year corrosion warranty. You may want to read the details of this warranty because the application of rust-proofing agents may void it.

If it makes you feel any better, none of the metallurgists or corrosion engineers that I know use or buy any of the underbody rust-proofing products. Your best weapon against winter salt is a good touch-less car wash with an underbody spray. Get the underbody rinsed frequently in the winter months to prevent salt build up, then drive the car to help it dry out. I like to go through the car wash close to my house on the way to work so the underbody has about 15 minutes of city and 10 minutes of highway driving to dry out after the wash.

Hope this helps.

Cheers,
TMQ

[tgwillard]

I would recommend not applying any rust proofing. My wife traded her 1990 240 on a 2005 S80. The day we traded it in, it had absolutely no rust. Our mechanic commented that he was surprised at the condition of the under body after so many years and miles. Rinse the under carriage during the winter when the temperature gets above freezing.

[MartinK]

Useful perspectives gents, thank you

[budrichard]

As another engineer with Metalurgy background, I second the above. In fact most of these treatments are actually detrimental to your Volvo as they can block the drain holes.
Look at my Volvo's specs. no rust!-Dick

[Mighty Quinn]

As another engineer with Metalurgy background, I second the above. In fact most of these treatments are actually detrimental to your Volvo as they can block the drain holes.
Look at my Volvo's specs. no rust!-Dick

Good point Dick! I didn't think about the drain holes!

Great to see another metallurgist around. We are a dying breed!