we don't really have one exact product we use .
because all the jobs and areas we have to get to are different there are a number of products and ways we go about getting into the hard to reach areas .
this 1940 coupe we are doing the work to is getting a Heidts IRS rear so some of the back half has been removed and is getting a new back half .
the chassis is a numbers match to the body so we are only doing the back half because of this . if it was not a numbers matching car we would just build another chassis .
so the front half has rust down the rails when the chassis was boxed years ago no one put any thing down the inner rails and it's got a good covering of rust .
so for the front half we plastic media blasted the chassis got in the rails as best as we could after it was cut .
we then run chimney cleaning brushes down the rails to get any lose rust off .
stood the open ends of the rails face down and got all the sand and rust out .it was a big pile of crap that came out .
we will coat the inner front parts of the rails with a converter I buy from theruststore.com .
we also use SEM rust-mort for things like this but because some of the rust is a little heavy I'm going with a product that is more aggressive .
converters will only work over rust they tend not to stack to clean metals .
after we coat the inner rails with the converter we will coat it with SEM's rust-shield along with the new and blasted metal . as SEM rust-shield is a all in one product (primer and top coat) we will pick a color from the SEM color deck (posted) that is close to the out side color of the chassis (Rot) .
if you have just some little rust spots down the inner rockers with the rest of the metal still in good shape and maybe even areas where there are still some primer left on them then doing it how we are doing the 40 coupe is not the best way .
for some thing like this you would only have to coat the inner rockers with some thing like rust shield .
we use rust-shield all the time for things like this . we do this so often we also have the SEM rust-shield mixing system .
things like when you replace the outer rocker and the inner or center rocker is rusted this way we will spot blast with a hand held blaster the areas we can get to and then coat every thing with the rust shield (new and old metal) after we weld every thing together .
the guns we use for stuff like this are the real cheap ones (photo) .
we make up our own tubes to get to where we need to . you want to use a more ridged type tubing so it just does not bend up on you as your pushing down the rails .
don't try a sprayable converter with this set up or reduce the SEM rust-shield . thicker is better !
when ever you coat the inner rockers always poke a piece of wire back up thru the drain holes to clean them out .