Removing old tar/mud everything

[EScanlon]

Except use the Marine Clean FIRST to degrease the metal, THEN do the Metal Ready to etch it for the POR to adhere well.

As far as comparing Scraping and Dissolving, it depends on your $ and time.

While I would recommend scraping off what you can before you start using the solvent of your choice, others have had a measure of success using heat. Carl's explanation as to the origin of the individual solvents I think serves to point out that the solvent's are flammable and as such should be used with care in that regard.

When I cleaned the underside of both my Z and the 1600 I used a combination of both. I scraped off everything I could and even tried for more. Then I used the mineral spirits and with one or two rags ended up with clean metal.

Then after further degreasing with Marine Clean (great stuff, yet it won't readily dissolve tar), followed up with Metal Ready and now the undersides are POR'ed. I went a step further on the 1600 and painted the underside with Chassis Coat Black to avoid the eventual sun-fade cloudiness of untreated POR.

2¢

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[Bart Hoedemaker]

Okay.. i tried some things today and the best method seemed removing as much big chunks as possible and then disolve with chemicals. It worked great. So that will be my way. Thanks for the help everyone!

I had a different plan for the underside, i want to zinkspray it first and then por15 or is it better to use metal ready instead of zinkspray. Because i think zink works really well to.

[EScanlon]

Haven't heard of zinkspray. So can't comment as to what it does, is supposed to do, or anything else.

Metal Ready is the etching acid (Phosphoric acid) sold by the POR folks to not only etch the metal for easy coverage by the POR, but also to provide some rust protection in the form of a zinc (zinc phosphate) bath.

While painting with POR you'll note that any area that isn't properly prepared to have some "tooth", that is an etch to it, will not be covered properly by the POR as it will have a tendency to film away. That is, the POR will pull away from the untreated metal. (Imagine if you will, laying down a bead of wax and then applying paint. The paint will not cover the waxed area.)

Not knowing the finish that zinkspray will have, it's hard to say whether the finish would be "rough" enough for the POR to cover properly.

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[240znz]

Just stick to the prep procedure that POR-15 recommends. You don't want to be trying "trial and error" procedures do you? As the last thing you'll want is for the POR-15 to peel off as Enrique says. All the work you are doing now would be in vain.

My car was not POR-15'd, but etch primed then semi hard chassis black paint and final body top coats plus clear. It's bloody bright under there. If I were to do it again, I'd paint the wheel wells black. Maybe if and when I change the suspension, I'll respray those areas.

[Bart Hoedemaker]

Changed the plan a bit, using an air needle-hammer, cleaning goes very quick now.