R34 underseal

[drifter17a]

I applied hammerite black wax which is kind of thick all under the car. Some light rust on surface but not too bad overall.

 

would the under seal stop further rust if applied over existing rust?

[GTSBoy]

51 minutes ago, drifter17a said:

would the under seal stop further rust if applied over existing rust?

Nope. You have to get rid of rust before covering it up. Now it can continue to eat steel behind the cover of hammerite.

[Rusty Nuts]

2 hours ago, drifter17a said:

would the under seal stop further rust if applied over existing rust?

Well you read the application instructions on the tin, and it says "kills old rust and prevents new rust" 

The problem is, You have to believe "snake oil claims" that something you paint on, removes old rust and stops new rust forming" Yeah Right" of course it does.

[tridentt150v]

I'd remove all rust you can get to and use a rust convertor first, paint it on and leave it to do its work.  It might take several applications and a few days to dry etc, but they do work.

[GTSBoy]

2 hours ago, tridentt150v said:

a rust convertor first

Which is usually phosporic acid based. Don't use other snake oils.