I have stripped my 69 442. The original paint was dead, so there are tiny little rust spots (akin to looking like overspray) that cannot be removed with a DA. The look more like stains, but you know they are rust. In the past I have sprayed the epoxy sealer over things like this with no problems. Then again, I never see the cars 5 or ten years later.

I was wondering about using Metal-prep or another rust desolver. Primary concern would be potential adhesion or failure to neutralize the "acid" correctly prior to paint. Any advice or experience with a particular product is appreciated.

Backrgound, I generally use all RM Diamont products with DE15 as the sealer and DP20 as the primer. The only change I make from RM products is the use of Rust Defender as a high build sealer/primer in place of the DE15 or DP20 if the panels are a little wavey.

Note, I don't believe in any of the rust converters (convert to primer). I had an adhesion problem on a frame once and would not consider it for the body.

 

I do know POR15 metal prep must be washed off after application and many other rust removers as well. You might get flash rusting afterwards.

 

MetalPrep, MetalReady, etc. are all pretty much the same thing - phosphoric acid.
They leave a thin coat of an iron phosphate compound on the surface, sort of like galvanizing, which leaves a coat of zinc.

If you use them according to label instructions, they should improve adhesion and reduce the chance of later rusting.

- Eric

 

Not according to SPI. I've heard on other epoxies not to use it either. I think your best bet is to media blast it off, or cut it out if the metal is too thin. I sprayed DP90 over light stained surface rust, the sales guy said it was OK. I'm not an expert, just an enthusiast doing the research for my own project.

 

News to me.

In the past, an acid etch was always recommended, even on non-rusted metal, to add extra protection against rust starting due to microscopic holes in the paint.

You learn something new every day.

- Eric

 

You need to check the info for the BRAND OF EPOXY you're using..."generic" assumptions are a recipe for problems with paints/primers, etc.

 

My experience with metal preps have been pretty lousy.
Some leave powdery coatings, and some leave gooey acid scale. Both of which are impossible to paint over.

Some paint over nicely, and then the paint sheets off a month later if it wasn't 100% clean.


If you use a prepping solution, you have to wash it off, and wash it off good.

Then, as soon as you wash it off, you will instantly get flash rust.

I'd rather prime over flash rust than acid scale if that helps you any.

 

I used Corrostop Tractor Paint and primer to paint my Cutlass, that puppy hasn't rusted one bit and we have really harsh winters here in montreal.

 

Thanks guys. I am going to stick with using the Clausen Rust Defender like I have in the past unless I media blast it. I read the Rust Defender application guide and did not remember that it advises against any use of a metal prep product. Hence, reading it confirmed my suspicions and experience in the past with adhesion problems.

I may have mislead you all by mentioning metalprep by name as I was really interested in a rust desolver. I had read something about products that only attacked or reacted with iron oxides and not the base material. I was probably in error thinking it was the trade name "metalprep".