This is a follow up to my question over on Oppo as to whether or not Phosphoric Acid would melt zamac.
Corrosive!
The short answer is No, but the long answer is going to take some time.* So, I was causing all my problems with spray paint but didn't know it...until now. I grew up building plastic model car kits, and if I do say so myself, I was pretty good. Especially with paint. Which is why it confounded me for so long that I could paint a 1:25 model car to almost perfection but not a 3 inch diecast.
The problem was over preparation. I cut, filed, sanded and even took steel wool in finer and finer grades to create the best surface to accept the paint...like one would with plastic when prepping for paint. Zamac is not plastic...
My over prepping left the metal too smooth for the paint to adhere, even the rougher primer paints would be flaking off with any handling.
(Which makes me wonder how folks can polish a zamac body until it's "chrome" and still get paint to evenly coat it, but that's a question for another time.)
While I was looking at two different applications of the same Rustoleum 2X flat white primer is when it finally slapped me in the face.
The same paint on both examples but the paint on the left has started shedding from the corners and high spots, after only minimal handling. The only difference was that the sample on the right soaked in phosphoric acid for almost an hour before being sprayed. No sanding, no filing, just a rinse under the faucet to neutralize the acid. The difference was life changing, to me anyway.
I picked a body fragment that had been stripped but never painted, and soaked it in a 3:1 water phosphoric acid bath for an hour. Center image is what it looked like after being washed. The right image is after 2 coats of rustoleum gloss white on top of the primer and I could not be happier. I've already started stripping older paint jobs that didn't come out the way I wanted, everyone gets another chance!
Now I need to get to work and start to learn masking techniques and I would appreciate any tips the more experienced painters can impart. I have a lot of time to make up... But, for now, the main thing is that I CAN PAINT!!!
*Long Answer: After seeing how much the phosphoric acid roughened up the surface of the zamac I decided to try a little experiment. Once it's nicer outside, I'm going to start soaking a car in the recommended solution strength and take photos every day until it dissolves. The label says 30 minutes-up to overnight for stripping metal, which, I've learned, is called Phosphotizing.
I'll let you know how long it takes! ...lol
Comments