Undercoating

from: https://rivperformance.editboard.com/riviera-talk-f21/paid-off-the-riv-t1673.htm

Jack the R: "I've read a few different times that rust proofing the underbody actually traps moisture against it and makes it rust faster. I had it done to my Charger 14 years ago and haven't noticed a problem, but I haven't had it up on a lift for inspection."

Jack, I wonder if that isn't dependent on the quality of the prep work done before applying the undercoat. I haven't begun researching this idea yet, but will keep that in mind.

I haven't heard that possibility mentioned before.

I don't see how the undercoating could be worse than having road salt splashing up onto the chassis, but this is what I have heard.

My opinion is, newer cars are designed/built with drainage systems. Look around and you'll see channels and holes near the bottoms of fenders and plastic panels. If you spray on thick undercoating material (it looks like tar), the drainage holes could become plugged. If this happens, moisture will build up inside, where there is no rust protection. Then you have a problem.

I'm not against rust proofing, but it has to be done right. Personally, I think it makes sense to buy your own and touch up the areas that need it.

On my Riv, there are small pockets at the bottom of the rear wheel wells, at the front side, that fills with dirt/rocks/debris. I have to manually clean it out. No matter how well drainage is designed into a car, there will be places that defy the odds.

True. And if you notice along the edges of the rear window there are tunnels for channeling water from the roof down to the trunk, which then runs out the back over the tail lights. Usually the chrome is worn on each side because of this. I'm always finding crud stuck in these areas. The trunk is easy to clean, the window edges are not.

I looked at mine today and it is flaking off in huge chunks. The area that was covered doesn't look bad though.

1998 Riv, I just came across an alternative to the Ziebart type undercoating - bed liner coating. I found a reference to it on Mopowerstyle -

Link

Post #3 -

Quote :

I know a few people that swear by spraying bedliners under cars they're building. It preserves the metal, hides some ugly, and is a good sound deadener.

It is a bitch to get of if you put it on!

The bedliner stuff is about 8X thicker than what Ziebart sprays on.

I come from the winter wonderland of Western NY so I feel almost qualified warning everyone about underocating hazards. Aaron mentioned the importance of keeping drainage holes clear so be careful using the bedliner as an undercoat, if you're going this route place stir sticks or straws into all drainage areas before shooting the coating and pull them out before it fully cures. More important is proper preparation and being careful not to trap the slightest bit of moisture, even small area with a little trapped road salt will start eating its way out somehow once trapped beneath the bedliner so clean it well and blow it off well with air a few times. I used to go every November to a guy in Niagara Falls Canada who would shoot old motor oil and parafin mixture all over the undercarriage..it was a mess but cleaned off easily with high pressure soap and water in the spring and kept most of the road salt damage at bay...they use alot of salt there and really rots the cars so badly most of us would garage our rides for the winter and buy beaters. Im driving my Riv this winter but making sure to keep the the chassis clean as best as possible.

With my car, i took ospho ( 20 bucks a gallon from ace hardware) and i sprayed the entire bottom of my car with it, turned all the rust into a harmless black chemical, then i undercoated it and i ahvnt had a problem. I used the rubberized undercoat from autozone.