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914World.com _ 914World Garage _ Wurth Metal Prep vs. cheap Ospho

Posted by: ChrisNPDrider Mar 14 2011, 08:59 PM

I'm adding bits to my online shopping cart and already have Wurth metal-etch primer and another can of satin trim paint. I've been happy with the Wurth spray paint I have used on my 914 over the 3 years of rustoration.

Now I am attacking the various degrees of rust in my interior. Tar is being removed, some holes will be patched and welded, gunk will be stripped, and interior will be sprayed w paint before new carpets go in.

I've been using the cheap, green Ospho rust converter from the hardware store, but is this Wurth product worth the extra cost?? Here's what they have on Pelican about it.

What works best for the $$$ and time????

Metal Prep
Metal Prep Rust Remover and Pre-Primer is a non-corrosive rust remover and pre-primer. This unique product prepares metal surfaces for painting and promotes excellent adhesion of Wurth Rust Guard. Removes all surface rust from brake parts, rims, brake drums, air lines and even from severely rusted metal. Able to restore rusted tools. Excellent preparation for any paint. Insures the best adhesion with your gas tank sealer. Provides incredible adhesion for the subsequent application of Wurth Rust Guard. Leaves a rust inhibiting zinc phosphate coating on metal. Better welding conductivity. Makes a positive adhesion to all metals (esp. aluminum and galvanized steel). Provides a smoother base for the application of paints, which guarantees a better "cosmetic look" when painting over uneven rusted surfaces. Easy-to-use one step process. Won't harm paint, rubber or vinyl. Non-Toxic, Non-Corrosive, Non-Flammable, Non-Caustic and has no harmful residues. Biodegradable Solution. Apply, let dry and then rinse with water.

WRTH-089091802

Wurth Metal Prep - 1 gallon [More Info]
$58.79

Posted by: sww914 Mar 15 2011, 01:19 AM

Ospho is mostly acid with a wetting solution. Wurth has some other stuff in it, zinc and who knows what esle. The Wurth is better. Nicer to paint over.

Posted by: Richard Casto Mar 15 2011, 08:31 AM

I would think you would want a product that includes both phosphoric acid AND zinc phosphate. I wouldn't use a product whose only active ingredient is phosphoric acid. When looking at MSDS for different products you find...

* Ospho does NOT include zinc phosphate.
* Both Wurth "Metal Prep" and POR-15 "Metal Ready" includes zinc phosphate

I would use the Wurth or POR-15 products. I currently use POR-15 "Metal Ready" as I can buy it locally pretty easy.

Richard