Rock salt, undercoating & lower body rust

April 1, 2010 | By Richard Prince


For those of us that reside in the Rustbelt, (I live near Cleveland), I would like to learn what measures might reasonably be taken to delay or eliminate rust formation on our vehicles, both newer cars, as well as older models that may not yet be classics. Yeah, I know, not driving them would help a bunch! I try to preach judgment in our family unit, particularly when the roads have been freshly “seasoned.” Unfortunately, my sermons typically fall on deaf ears.

Needless to say, Rustbelt drivers are basically sacrificed to the ferrous oxide gods and at the mercy of ODOT and local community snow removal services. For the record, I have a 1997 F-250 4X4 with only 54K miles. I bought it new. The truck was used only sparingly for summer towing, and on occasional errands when the accumulated white stuff demanded a bit more ground clearance and traction than the family sedan could muster.

Unfortunately, the truck rests outside on a gravel parking area. Consequently, the years have taken their toll and the underside is fairly deteriorated, although the exterior (topside) looks almost new. I just bought a new GMC replacement, which will be used in a similar fashion as the Ford, and would like to do what I am able to do (short of building another entire storage building) to minimize rust formation. I’m

told that newer cars don’t benefit much from current undercoating/rust proofing techniques. (Something about the new alloys and coatings currently used in the manufacturing processes of new vehicles.) Some also claim that the human error of rust-proofing application may leave the vehicle more vulnerable to moisture and rust than would otherwise result if the vehicle were left “bare.”

Also, I continually hear claims of additives being placed in public snow removal chemicals that are worse than the old salt formulas.

I’m also aware of the negative electrolysis-type devices, which claim to inhibit the formation of rust. Now there are claims of actually reversing the rust process. However, I don’t know anyone that has installed either one of these devices, although I’ve read claims of success on the Internet. Needless to say, I’m skeptical of what claims are offered on the Internet, particularly when they may be profit motivated. Obviously, the rumors regarding preventative measures (against rust) are abundant.

I’m certain this will not be a new query for you but nonetheless your response would be appreciated, especially for those of us that are tired and broke from dragging rusted vehicle carcasses to the junkyards.


It’s my understanding that most municipalities use a blend of different chemical compounds in their efforts to fight road ice. Some of the ingredients are more corrosive and others are less corrosive. It’s in everyone’s interest for government to use the least corrosive chemicals that are still effective. Besides eating away at our beloved cars, the ice-melt compounds also attack road surfaces, bridges, tunnels, drainage systems, landscaping, and just about everything else they come in contact with. But as with everything in this world, the issue normally distills down to one of benefit versus cost.

The most common and least costly product is good old-fashioned rock salt (sodium chloride). Though inexpensive, it is highly corrosive. Other compounds such as potassium acetate, sodium acetate, sodium formate, and urea are considerably less corrosive than rock salt but they cost significantly more. Despite the added cost for the product, the longterm cost to society is probably much lower because of decreased damage to infrastructure and the environment.

So, in answer to your question about additives in the snow removal compounds that are worse than salt, chances are the additives now being used in most places are actually less corrosive.

Regardless, any way you look at it, whatever they put down on the roads is corrosive to one degree or another and the only way to really escape their ill effects is to store your vehicles all winter or move to a place with a friendlier climate.

I do not believe that electronic devices that purportedly stop rust or reverse the effects of rust really work and therefore don’t recommend them.

I’m also not a big believer in undercoating a vehicle. If undercoating is not applied on a completely dry vehicle on a very dry day it can actually trap moisture against the very surfaces you’re trying to protect. Sloppily applied undercoating can clog drain holes, thus promoting water retention and corrosion.

Undercoating applied over dirty or improperly prepared surfaces can adhere poorly, making it ineffective at best and at worst forming pockets for water and dirt to accumulate after areas of undercoating separate from the surfaces they are not sticking to. Intelligently applied high-quality undercoating can do a lot to protect against corrosion but poorly applied or low-quality undercoating will do more harm than good.

How do you ensure that you’re getting an intelligent application of high-quality undercoating?

Aside from doing it yourself, which is a messy and difficult job, there’s no easy way to ensure good results.