Attention chemists! The weather is reaching into the mid-50's here tomorrow before falling, so I have a narrow window of "nice" weather. I am going to spray Rustoleum gloss black reduced with acetone on a bunch of control arms and other misc parts.
I have some leftover PPG urethane hardener that I'm considering adding to improve durability and speed the dry-time. Is this a good idea or bad?
As a former Sherwin Williams paint rep I can tell you it's a crap shoot. It will probably work, but you should always stick with known compatible products unless you don't care about having to re-do your work. Adding harderner does not speed the dry time. In fact, if you over catalyze it may take days to dry. The hardener works by a process called chemical cross linking which reates a tighter surface when cured. The total cure through can take up to 30 days, although the parts will be safe to handle within hours to overnight depending on mixing ratios and temperature.
I'm no chemist, though I work at a chemical plant.
You haven't given us much info. Rustoleum has a LOT of product lines:
Rustoleum brands- 2 pages worth
I am assuming you mean Rustoleum Stops Rust, which is acetone based. So, the acetone would be correct.
But the hardener (MEKP?) is a catalyst, designed to work with urethane in specific quantities. I'm not convinced it will give the desired results.
Wait for better input than mine.
why not try a test piece
... and report back to GRM
he may be on to sumthin'
I don't think you can mix a urethane hardner and an enamal paint. I did work in a body shop supply store and mixed countless gallons of Dupont.
Yes, it is indeed Rustoleum Stops Rust gloss black #7779. The leftover hardeners are from the PPG Omni line - they're the kind that say "must use within 14 days of opening". That was 2+ years ago. MH167 and MH165, and are from the Omni AU (Acrylic Urethane) line. I used to have some AE (Acrylic Enamel) but that's gone now.
I had great luck putting MC161 clear directly over MP170 epoxy primer on some parts, and I've also successfully put the MC161 over Duplicolor high-temp engine enamel. Unfortunately I think its just too cold here to try something like that again. I bet the epoxy would be OK but the clear might not. Even though the Rustoleum won't look as nice, it will be easy to touch up in the future.
Temp is another concern, I can't help I've never painted.
I am a chemist, at least I play one at work, and without a bunch more info on the composition of the paints it is the definition of a crapshoot.
Given the size of the parts it might be simpler to just raise the temp in a small area of the shop and paint to the spec on the can.
i used Rustoleum straight out of the spray bomb cans on the subframe and front suspension pieces of my Nova- a couple of coats of flat black on the (slightly rusted but cleaned up with a wire wheel) bare metal and a couple of thick coats of semi gloss over that.. in the 3 years i had that car after doing that, i drove it on i don't even know how many gravel roads at speeds that were definitely above the recommended speeds and jacked the car up countless times, and there wasn't a single scratch or rock chip that i could see on anything when i would get bored and clean it up a bit... it was between 30 and 40 degrees in the shop when i sprayed it- that Rustoleum is (or was 10 years ago) pretty magnificent stuff that didn't need anything added to it to make it durable. so unless the stuff you buy by the gallon is different than the stuff they put in the spray bombs, i wouldn't screw around with it.
Rustoleum is an Alkyd paint.
They offer their own catalyst
But Majic paints at tractor supply have their version of an Alkyd hardener
And Van Sickle tractor paints do as well if you have a local shop that carries that like I do.
My painter got wide eyed when I just asked if a urethane hardener could be mixed into an oil based enamel and jsut said "NO!!"
The gloss and finish of Alkyd paints are massively improved by the catalyst. In this photo you can see that I repainted the front quarter with the catalyst as opposed to the rest of the car without. The shine just stopped at the blend line
Please note, this was a quick and dirty, make it one color driveway paint job that wasn't even a 20 footer, more like a 20 yarder. I was just trying to represent the difference in gloss the crosslinking provides. It also makes the paint much more fuel and solvent resistant. Carb cleaner would wipe off the non catalyzed paint.
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