SPI epoxy primer after panel treated with phosphoric acid

As far as I know, Simple Green has citric acid in it along with a PH buffer, but I am not a chemist. I do know that I have never seen it recommended in a tech sheet for metal preparation prior to refinishing. It is a pretty decent first step to re-painting an existing finish, though.
you are right, its citric acid. I guess I meant was it works the same way a dilute muriatic acid will work on metal to remove oxides and scale.

As far as the wire brush deal and scratching back with 80, I really cannot agree with doing that. You might as well skip the ospho step. The white dusting is excess, molecules binding together, creating a film, just seems like you are removing the good it did.
 

123pugsy

Member
you are right, its citric acid. I guess I meant was it works the same way a dilute muriatic acid will work on metal to remove oxides and scale.

As far as the wire brush deal and scratching back with 80, I really cannot agree with doing that. You might as well skip the ospho step. The white dusting is excess, molecules binding together, creating a film, just seems like you are removing the good it did.

Sorry, but a film of what?
 
the actual protective phosphate film that the ospho creates. I do not know what they are doing now, but the auto manufacturers were using washers, like industrial paint washers to iron or zinc phosphate the entire car before paint. That is a treatment to metal which puts a protective coating on the metal to make sure the metal is clean and help paint adhere properly. If you watch a how its made type program, you seen the entire inner structures going thru tanks to prep the metal for painting. I do not know if they are still doing this or moved to an ecoat type of dip and primer. Its where every industrial paint job starts with a iron, zinc or manganese phosphate coating before prime and paint.
 

crashtech

Combo Man
In the case of Ospho, dry sanding it might create a hazard because it contains a bit of hexavalent chrome. If Barry has tested it to work and put it in the Tech Manual, you can take it to the bank that any extra sanding step is unnecessary. Phosphate and chromate coatings have been used for decades to treat metal prior to refinishing, as anotheridiot says. Typically they are used improperly, though, which is why SPI said to avoid them completely for many years. Ospho must be one of the more forgiving ones.
 
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