I have heard about 50/50 on that. Some say it will some say it wont. I have never seen a car with rust under the undercoating. That does not mean it doesn't happen. There wasn't any rust under the undercoating on my 69. I'm not sure how good of a comparison that is though the car had very little rust anyway.
When we began work on our 65 there was some rust under the undercoating in places. Luckily it wasn't bad and it didnt need to have sheel metal replaced. The rust was there though.
I have seen other cars that were rusted out behind the undercoating.
are you sure that the undercoating wasn't sprayed over the rust to hide it at some point? I am always suspicious when looking at a car that has a nice or to fresh of a looking undercoat on it.
I plan to repair my bad rust, then wire wheel the entire underside, spray a rust encapsulator, prime then coat w/ flat black and call it good. My car will likley see little rain/snow.
are you sure that the undercoating wasn't sprayed over the rust to hide it at some point? I am always suspicious when looking at a car that has a nice or to fresh of a looking undercoat on it.
I don't think it was to hide the rust. At least not on my car because the rust was very minimal and the undercoat was ancient.
On the other cars I have seen, I'm sure some of them could have had the undercoating applied to hide the rust. There is really no way of knowing. I know that the undercoating on some of them was really old as well.
I plan to repair my bad rust, then wire wheel the entire underside, spray a rust encapsulator, prime then coat w/ flat black and call it good. My car will likley see little rain/snow.
This is basically what we have done to ours. I can't remember exactly what all we did. I was 15 and this was over 15 years ago that we did that work on our car.