Verdict - 70% fail 30 % pass. I would be better with using oil or wax to fight rust. Next one that I will use when will buy new used truck will be cosmoline.
This was my truck in 2009 when first paint with cgc from rustoleum at undercarriage. I did it once per year.


This is in 2019.


That said CGC worked at frame. Only place at C frame of my pickup Where is a 1" size hole is where I wasn't capable to spray from inside because a angled frame member is there. CGC manage to hold my exhaust healthy to as my fuel tank. Yes you can spray Cgc at exhaust.


Another helpful thing is that bolts sprayed with CGC will not rust and you will be capable to remove it. See that bolt in picture that is 20 years exposed to MN winters. And you can see that box frame how is rusted at edges but still work at middle. CGC work but I do not believe that is better then oil and waxes at undercoating.

Well this is my contribution to humanity as I didn't see anywhere someone did it with CGC.

 

Great post, and WOW what a difference in ten years!

Good information for all who are interested!

 

3. photo who may interest. You can see that rust hole is exactly at middle of angled frame member. You can see angled frame member 2 bolts head left and right at bottom of C frame members. So imagine what would be from that frame if it would be O, so called boxed, frame or if I would not use CGC along frame. So basically 6" of frame that was semi boxed and hole is right there. And as I said nowhere else.

 

check out some of the guys in Canada and what they do.. I have heard they have a product like motor oil that is sprayed on the bottom of truck and inside the frame.. They drive down a gravel road and get the oil COATED.... They tend to do this every fall or every other year to keep the rust a bay......... Many places in Canada... and some of them call it "UNDER COATING"..

 

^^^ It is Krown than they use in Canada. Main idea of my post is that oil/waxes are better than paints for home yard painting experts.

 

Yup Yup Yup. The good 'ol farmers treatment. Don't want it to rust? Coat it in oil.

 

Cold galvanizing compound by nature needs direct contact with the bare metal.

 

The trucks not doing too bad but you should address the tailgate dent.

 

^^^ Truck is in perfect mechanical shape and I plan to keep it for years to come. Frame is in perfect shape too.

 

I guess therefore it worked so well at exhaust. Should it work well where paint crack too? Like original paint crack but CGC do not allow rust chime in.

 

As far as CGC touches the bare metal at the paint crack or peel, it should work.

 

Wow that is rusty! What area of the country do you live in? Did you wash it regularly?

 

^^^ I'm in MN to. I did wash it regularly once after winter (sarcasm I guess). Washing will not help you if you have boxed frame. It is 20 years old. Frame is almost like new. Again it helped at bulk metal like frame and calipers etc but not at sheet metal. Maybe as above guy said because sheet metal was painted. Cosmoline is next to try at next truck. Only problem is until I finish this testing, 10 years for one approach, can pass away. Well again no joke, 10 years experiment. Compare it to youtube experiments where they expose metal to elements for one week. Big thing is I didn't spray inside of closed panels like rockers.

 

"Looking back over my shoulder" should spray one half of car with CGC and other with Cosmoline.

 

You could coat that in whatever you want and it will rust away if you don't wash regularly during the winter. Yuck.