Painting a cold cast aluminum helmet… Please help this newbie!

[FettOnFire]

Hello! I am a complete newcomer to both this forum and creating Mandalorian helmets. I've always wanted to try one… my wife and I are going to Burning Man (in just less than two weeks) and I decided to take the plunge and make a helmet as part of my costume. This forum has been an immense help (although like any other hobby, the deeper you go, the more it seems there is to learn). I bought a cold (re?)cast aluminum FP helmet off Etsy and have already buffed the entire surface with 0000 steel wool to remove any release agent. Now I've taped off the areas I want to remain aluminum and am ready to paint, but I'm seeing conflicting information in my Google and forum searches.

I'm going to paint the entire unmasked surface white (priming first) then apply a stripe of neon pink down the right cheek and over the head (see my avatar). If someone with experience here could please clarify for me: I'm definitely going to prime, then paint — do I need to sand the unmasked surface first? Or will the primer stick to the cold cast aluminum as is (now that I've thoroughly removed the release agent from the casting process)? What type of (spray) primer and spray paint should I get for this project? It doesn't have to be the most perfect job (since this won't be screen accurate or much of a collector's piece after nine days in the desert), but I'd like to do it as "right" as possible so I can keep it for the memory.

I am grateful for any help or advice offered, I really feel up against a wall here as I don't want to sand and scratch the whole thing so primer and paint will stick if it's not necessary. I have made a good faith effort to find a clear answer on Google and on these forums but there's some contradictory info. Thank you! There are some incredibly cool helmets on this site!

 

[MinuteFett]

If you've already cleaned It off then there should be no issues and no need to sand, especially since you already hit it with steel wool.

I suggest priming with Rustoleum 2X primer(NOT PAINT AND PRIMER), and then go at it with rustoleum paint again. For the white, you could possibly even get away with just spraying a couple coats of white rustoleum primer.

I have used this primer time and time again without fail.

Good luck!

 

[superjedi]

Cold cast has powdered aluminum mixed into the resin (or gelcoat). For priming metal, take a look at a self-etching primer. They're designed for metal and give a little bit of "bite" into the surface. Rustoleum makes one and I've used it several times before.
Whatever primer you go with, make sure it's fully cured before you apply your color coat. Especially if you're going to use tape to mask off stripes and stuff.

 

[Grimstuff]

Yeah I'd definitely go an automotive primer, self-etch or universal bonding primer will be good bets. I'm not a fan of the more regular paint primers that have the standard 48hour recoat windows, they're pretty much just really matte regular paint. You'll definitely want something good for surfacing metallics.

And yeah as said, sounds like you've already done the prep you need to with the steel wool. You can sorta make double sure by running your finger across the surface a few times, if you see any metallic dust transferred to your finger, then there's still too much loose metallic powder. Surfacing cold-casts and metallic paints can be really tricky with that since they pretty much are just dust. Personally why I avoid coldcasts and just do metallic effects with a laquer layer.

I'd also really recommend getting a delicate surface masking tape. I've had a great time with Frog Tape Delicate. Worst feeling in the world to lift your tape and have it pull all your paint away from the metallic. Also don't leave any masking tape on longer than 3 days or so, as even the weaker tape adhesives can form a stronger stick over time.

Also, when/if you clear coat, go very gentle in very light layers. I've notice heavy clear coats can especially cause wrinkling of paints that were surfaced on metallics, even when they're fully cured. Go for testors dullcoat if you can find it, I've never had it wrinkle anything.

 

[Grimstuff]

Oh, and if you want some material to do tests on before you paint the proper helmet, cutting out the visor plastic first will give you a big chunk to play with.