Painting cast aluminum parts

So today I left the 15th annual Cabin Fever Expo in York, PA lightheaded
because of the engine exhaust fumes but not empty-handed. I've used the
occasion as an excuse to buy myself a mechanical toy in the past but this
time I felt emboldened (or it might just be all the fumes again) and
bought a machined Steam Engine Kit #5 by P.M. Research that requires
assembly.
Now my challenge is to deburr, de-flash and paint the cast parts before I
can begin the assembly. I know that for most of you hardcore machinists in
the group would not consider it a challenge but I haven't done anything
like that before so that'll keep me busy for awhile.
The question naturally arose: "what paint to use?" The young fellow
selling the kit to me was honest and said he's just running the booth
until his dad comes back from lunch. And I badly needed some fresh air and
could not hang around for much longer. The assembly manual says: "Use
proper metal primer" and mentions no actual paint.
So, what would this respectable group recommend for the primer and the
paint? And where do you get it, is this something a mere mortal gets at
Michaels or A.C. Moore - type craft store or is this a special order
paint?
There won't be any actual steam there (compressed air) so there isn't any
high-temperature requirement but I really want to use the right stuff
because I sincerely hope this won't be my last project of this kind. I may
even get around to buying a lathe and a mill at some point in the future
and do a project that requires machining (long shot at this point tho).
That's what visiting a show like this does to people :)
Also, I've heard/read/seen on TV that (some) metal paint requires baking.
As much fun as it would be to mess with it in a home environment, I don't
think I'm properly equipped for that, so a self-drying paint would be my
preference.
Thanks for any information, tips or comments!
Reply to
DA
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Rustoleum spray-bomb should work fine. Use their metal primer first, then the color(s) of your choice. You _can_ do a good job with spray-can paint, but not the first time you try.
Reply to
Tim Wescott
Surface prep is Critical.
Clean! No dirt. Minimize surface oxides.
Degreased! Use lots of paint thinner to eliminate finger oil for example. Change application cloths often so that you don't simply smear grease around.
Dry! Paint the object, not the fluid on the object.
Temperature is Critical with rattlecan paint. Rig up an Air Oven if you want your paint to stick. Adjust the temperature of your parts towards the high end of the recommended temperature on the can. When you ignore this advice, you will be rewarded with a tacky surface that never really dries and falls off under fingernail pressure.
An 'air oven' can be as simple as several flood lamps aimed at your part from various angles. I used a length of air duct with a floodlight inside. It provided a nice convective flow of warm air through the parts that prepared them for painting and dried them properly after painting.
Paint only in a well ventilated area.
--Winston
Reply to
Winston
I would scrub everything in lots of hot water and strong detergent, and then wear rubber gloves afterward to protect the part from finger grease. Solvent is nice as a last step, but it takes lots and lots of it to remove large amounts of grease.
Reply to
Tim Wescott
Good Grief! Unbunch your panties, go to any autoparts (Pep boys, Kraken) or home improvement store or any hobby shop, and just get any ol' paint! OK, not "Any ol' paint" - probably not latex wall paint, but some kind of enamel. If it's not going to be subjected to any abuse, even lacquer would work.
Just be sure the parts are clean and you follow the label instructions on the paint itself, and you'll be fine.
Some may recommend zinc chromate primer; I won't argue with them, but it's probably not necessary, although it might make you feel more comfortable with your paint job on your new toy. :-)
Have Fun! Rich
Reply to
Rich Grise
I might recommend zinc chromate primer, if I thought you could find any. They eliminated using zinc chromate primer where I use to work about 15 years ago as the chromate is hazardous to your health. This is not to say that you can not find ZCP, but it will not be easy.
Dan
Reply to
dcaster
A phosphoric acid wash never hurts either - like Aluma-Prep-33 (or simple water softener resin cleaner - virtually the same stuff) (Phosphoric acid and ethyl polyol)
Reply to
clare
Oops! Apparently I've been "out of the loop" too long.
Thanks for the heads up! Rich
Reply to
Rich Grise
responding to
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Wescott wrote:
Thank you for your replies, guys!
Yes, I will clean it well before doing anything. Thankfully, the parts are reasonably clean to begin with, some of the flashing has already been removed and they might have even washed the parts already but I'm going to do it again anyways.
I see that the primer is the most important part of this combination. From the looks of the parts, especially the body that is kinda open, i.e. needs to be painted inside as well as outside, I think I'm going to stay away from sprays for both primer and the top coat. It looks like it would be a challenge to cover it well from a spray bottle.
So, I've found this Rust Oleum 8781-504 Aluminum Primer in 1qt cans on Amazon :
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which looks like it'll work. As far as the top coat - I'm not sure yet. I'll just browse HD or Lowes for some more Rust-oleum stuff.
Thanks again!
Reply to
DA
See if you can find someone local with an ultrasonic cleaning bath.
Reply to
John R. Carroll
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Geez! Get the schmutz off, but there's no point in being obsessive about it.
It doesn't have to be hospital-sterile. If the parts are small enough, running them through the dishwasher (if they'll fit) will be more than good enough, as long as you don't load them up with finger grease when you unload them. I'd apply about the same standards of "clean" as if I were hand-washing my own pots and pans.
But they _do_ need to be dry!
Cheers! Rich
Reply to
Rich Grise
It's pretty cheap these days. He might even find a local guy to do it for free. The advantage is that anything in a pore is removed.
Reply to
John R. Carroll
This stuff makes a huge difference with aluminum. It completely degreases, and leaves a surface that really holds paint. It makes any paint wet better and flow out nice and level. Aluma-Prep 33 is made by PPG or Ditzler and is found at places that sell paint and supplies for auto body work.
Reply to
Don Foreman
...
Ah, pores! Okay, I've learned something today. I guess I can go back to bed now! ;-D
Wait a minute - how do you know that the new coating will go into those newly cleaned pores? Or does it just naturally go in by capillary action or surface tension or adhesion or something?
Thanks! Rich
Reply to
Rich Grise
Run one mostly-complete cycle using detergent so as to thoroughly clean / degrease and then restart, this time without detergent but instead adding a mild alkaline to the first wash cycle--IIRC your ph needs to be slightly above 10....if your water is hard or if the is ph excessive then you might want to run a separate final rinse cycle using distilled water by temporary unplugging the water solenoid and filling the tub by hand so as to avoid mineral precipitation.
Reply to
PrecisionmachinisT
responding to
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A phosphoric acid wash never hurts either - like Aluma-Prep-33 (or
Thank you for the reference. Yes, I would much prefer something that works yet makes no fumes (or less than paint thinners, anyway).
However, I was looking for sources for the cleaner and found this page at Henkel
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that describes a product called Turco ALUMIPREP 33 'Cleaner and Conditioner for Aluminum' - judging by similarities in the name and that they do mention phosphoric acid, I think it's the same product. It looks like they do NOT recommend it for castings:
"Turco Alumiprep 33 should not be used on high copper bearing aluminum alloys or aluminum castings."
Not on castings? Can someone who worked with phosphoric acid cleaner comment on that please?
Or, and I do get Rich's comment about this not having to be hospital-clean. Indeed it probably shouldn't be. But to paint these parts properly is just a part of the fun for me - it is, after all, a hobby project. That's why I keep bugging people with questions :)
Reply to
DA
I didn't know that about Alumiprep.
You're both right. There's no such thing as too clean, but paint isn't nearly as fussy as anodizing or plating.
Reply to
Don Foreman
"Not on high copper bearing ----- castings"
Aluma-prep and alodine are both used on many aluminum castings (like aircraft engine crank-cases)
The ResCare product is roughly 10% of the cost of the Aluma-Prep and has virtually the same composition. Readily available at plumbing supply and home supply stores everywhere.
Reply to
clare
EEEK! OP didn't say if any of his parts are aluminum, but alkalis eat aluminum for breakfast.
Hope This Helps! Rich
Reply to
Rich Grise
Please allow me to remove my foot from my mouth. Right after hitting "Send," I bothered to look at the subject line.
I will now give myself forty lashes with a wet noodle.
Thanks, Rich
Reply to
Rich Grise

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