Technical Phosphoric acid and body putty question

I am trying to get my panel ready to paint and am going to be using Phosphoric acid to kill the rust that's left after stripping and wire brushing. I have done some fairly extensive repair on the left rear quarter and tailpan and was wondering if the phosphoric acid will have any negative effects on the body putty. And if so can I shoot it with epoxy primer in those areas to protect it and then go with the acid on the rest?

 

I wouldn't do it. The filer is going to absorb the acid solution and cause you endless grief later on

 

There's going to be some reaction.
There's some epoxy that will just about jump off phosphoric acid treated panels, there are others that will work fine on those panels. The epoxy would be your barrier. The fillers can go over top of the epoxy no problem but the level of metal finish should be pretty good.

 

Bringing this back to the top. My question really is: If I shoot the filler areas with epoxy primer will it protect it from the acid?

 

It depends on the epoxy. Some are fine with phosphoric acid and some are not. Check with your paint rep.

 

Read post 3
The short answer is yes but ,,,,,,

 

DuPont's "Veriprime contains phosphoric acid and we shot that over auto body filler with no problems.

You used the word "putty" I hope that you are not using nitrocellulose putty or any other non- catalyzed filler. (a definite no no.)

 

Etching primers have a weak form of phosphoric acid in them to give the etch. If your panels are rust free with the exception of some left over pitting, you would only need to treat those areas with mild phosphoric solution on a rag then wipe it with a fresh water rag to remove excess after the etch.

Phosphoric acid solution turns light deposits into iron phosphate very rapidly so it doesn't take a lot. Heavier rust deposits take more treatment action to convert all the deposits over. That's why it is sometimes refered to as a conversion coating.

 

I would just use a self etch primer and forget the acid, just as previously said Dupont Veri Prime has a weak solution in it. I have used Vari Prime for years and have good luck with it