I have some rust spots forming on a fender and the frame of my '95. Being the cheap guy I am I went through the MSDS of a few undercoating and noticed they are made up of asphalt as well as a few other ingredients to thin it and propel it for aerosol use. So I went to the closest home store and got a gallon of asphalt foundation/roof coating. So I applied it to a spot inside the fender I had welded as well as a spot on the frame and inside the fender lip where it's beginning to rust.

I'll throw up some photos and keep an update on how it dries and if it becomes flaky or chips off easily. I do know it needs a small amount of thinner added to make it spread a little easier. Overall I'm hoping to use it as an undercoating on my vehicles because at $9/gal it would be economical and I have not been impressed with the aerosol types because they go on very wet and have so much thinner that it takes a week to dry to the touch and even longer before a leaf doesn't scratch it off.

 

I see auto correct did me no favors on the title.

12 hours since application and it is dry to the touch everywhere but thick spots (1/16" or more). Next step will be mixing a small amount with a thinning agent and see how it applies as well as dry times. I will do 2 coats with both styles and perform a few scratch test to determine how it compares to the factory stuff they spray in fenders. I know it will be softer since it doesn't have the same 20 year time on it but I'll do the scratches every week and see if there are changes over a month to the durability.

 

Good idea checking the MSDS. Amazing how much money you can save when you know what it is. Something like "Engine Flush" at $8 a quart, when you can buy a gallon of kerosene for $4. I'll be watching this thread, thanks.

 

17 hours after application and it is soft enough that a fingernail takes it off slowly. That is only 1 thin coat and moderate nail pressure. Overall it is much more durable than the aerosol version if you want something quick and easy.
I'll get some thinned coating made up shortly and see what happens. It's raining here so it will be a humid application to really test adhesion as well.
I'm sure the factory stuff has some kind of hardener in it but even if this needs touched up every 5 years it's still a fraction of a professional job and provides more protection and sealing of panel seams than nothing at all.

 

Well, the aerosol stuff I put on the gas tank is pretty hard now so I'll call it a wash. I do believe using the stuff right out of the gallon can decreases dry time because it is a lot thicker. When I put on a second coat it seemed to make the original soft again. So multiple coats does nothing to the dry time. So if I had to make a decision right now I'd say it's just as good as aerosol with a lot shorter dry time. Application is difficult because it's thick and finish is terrible as well. But if your using it you probably are going for function over looks.
I'll continue with the tests but overall it's exactly what I am looking for as far as quick and very cheap protection for frame, inner fenders and any underbody panels or parts that need protection from road salt or places where there is a buildup of dirt/grime that can lead to rust.
Just my $.02

 

Thanks TZ, good info

 

Here's a pic of one area with a very thin coat.


Here is the welded area which was rough to begin with but I just globbed it on. Can't really tell the difference other than the old stuff is dirty and faded.


I have applied it in a few other spots but didn't get any pictures. These are the two places I will be doing scratch tests starting this weekend.

 

i will be watching this thread as well. looks like pretty good info. thinking i might do this over my whole truck (instead of a rhino-liner) if it seems to hold up.

 

I doubt that would be good since it's asphalt. In other words tar. Park out in the sun and it could start to run off.

 

I failed to report last weekend but after 1 week it was firm to the touch but could be picked off with a fingernail. Tomorrow will be 2 weeks since application. So I'm guessing it would hold up to normal wear/tear but would not take much abuse as far as rocks. In that case you would probably want to do spot checks and touch up any damage. Overall it's less messy and a faster dry time than the aerosol versions. If you want something that has better protection you better pay to have it done. Otherwise it's very cheap protection beyond what comes from the factory.
I'll update tomorrow however I have someone looking at the Blazer this weekend so the end might be near for me on BlazerForum.