What paint to use for a hard durable coat on aluminium chassis?

[mort]

I've been using acrylic water based paint and a poly clear coat and it comes out looking great but it's not very durable. What's a good economical paint and clear coat to use to get a hard and durable coating that doesn't scratch away very easily? I'd prefer to be able to buy a few colors and mix my own shades if possible.

I tried a self etching primer and then my paint and clear coat but it still wasn't very durable.

Thoughts?

[J M Fahey]

99% of water based paints can easily be scratched fom any non porous surface.

And aluminum transparent oxide surface, akin to glass, makes it harder.

I use:

1) pre etch in a water-lye solution (1/4 Kg lye in 10/15 liters water)
It starts bubbling , slowly at first, faster at the end, and surface loses typical aluminum brightness , becomes dull silver.
May take up to a couple hours at ambient temperature.
This FULLY removes surface oxide, grease, fingerprints, etc. and leaves surface porous.

2) after washing and drying apply 2 component wash primer

3) after 1 or 2 hours (depending on ambient humidity apply final coat of paint.

Anything from Nitro or Acrylic car paint (what I use) to standard household oil/Sinthetic enamel (the kind which stinks, makes your eyes cry, takes overnight to dry and is only really hard after a week but after that keeps oxidizing/curing and in a year is almost impossible to remove) to "oven dried industrial paint" , similar to the household one, but never dries on its own, only after proper time in an oven (they provide you with a time/temperature table) hardens like a rock.
Itīs the typical paint used for tools, industrial furniture, electric motor cases, fridges, roof fans, etc.

Itīs the strongest and cheapest but requires an oven (or equivalent, such as infrared gas screens, etc.)

Maybe instead of investing for just a couple chassis itīs better to have a *good* car body painter do it.
Specially those who paint buses and commercial trucks, because they know how to paint aluminum.

EDIT: I am starting to experiment with a new wonder paint, here called "Multimetales" because it can paint *any* metal, including aluminum and galvanized sheet without any special treatment . (incredible).
http://www.pinturasvenier.com/pintur...ltimetales.htm
Just wash with water and detergent to remove grease and dust and let dry.

Apply 1 layer, let it dry, apply a second and thatīs it.

Water based, no funny smells, I guess it still takes overnight to fully dry, no problem with that.

Itīs so sticky that itīs recommended to paint kitchen and bathroom tiles, go figure.
http://www.prestigioweb.com/Blog/44-...de-venier.aspx

Iīm sure there must be something similar in USA.

It dries dull/satin/matte so it requires a transparent overcoat afterwards.

EDIT 2: agree with RG keen, 2 component polyurethane is incredibly adhesive and hard.
On aluminum it *still* requires proper surface preparation.

And guys who paint motorcycle gas tanks and frames should have experience on that.
Just make sure that besides steel they also understand aluminum peculiarities.

[R.G.]

Laboratory-grade cleaning and chemical removal of oxide, followed by a self-etching primer, followed by a catalyzed urethane paint.

Catalyzed urethane paints are toxic before they react and "dry", but they're about as hard as any paint.

You could also look into powder coating. Most towns of any size have a shop that will do powder coating; they're often motorcycle customization shops.

[ron vogel]

or just buy a $99 harbor freight powdercoating kit. I used to use one for automotive parts...worked great for a cheapie

[J M Fahey]

Just curious: how do you cure/melt/fix the powdered paint afterwards?

[ron vogel]

Just curious: how do you cure/melt/fix the powdered paint afterwards?

It's got to bake at 300F for 20 minutes. Best way is a convection or toaster oven dedicated to only PC use. You shouldn't use an oven that food will be cooked in. I just used a heat gun into a cardboard box; worked great. Sounds sketchy, but it works. Just can't have the heat gun pointed at the part, and I made a mount for mine. Cardboard won't ignite until 451F, and my box would generally be in the 300-325 range with the heat gun (have an IR thermometer handy). For larger parts I had a plywood box. Both the wood and cardboard are excellent insulators. Basically, you hang the part from a wire and coat it over a tarp. I tied my wire to a brazing rod, and after coating carried it to my box. The top flaps of the box had a notch, so I drop the part down into the box, then closed the flaps. leaving only the notched hole exposed, and the brazing rod sat on top holding the flaps down with the weight of the part. The powder will fall off if touched or banged into, so it has to be handled carefully. After baking for 20 minutes it's ready to use once it cools down. I also should note, during baking the part should be checked that all areas should look "wet" before you start timing it.

The powder IS explosive, so always work in a well ventilated area...if not outside. I tested it once by throwing some powder up in the air, and hitting it with a blowtorch. Trust me, it will ignite!

Now that I scared the crap out of you, I should say, it's not that bad....and in the grand scheme of things it's safer than working with spray cans if you aren't a complete moron around it.

Pic is of a fuel rail I made for someone, powdercoated red.

[J M Fahey]

EXCELLENT , Iīll try to see whether something like that is available here.

I can get expensive "real" industrial equipment, way over my budget, but nothing for $99 home use.

In my case Iīd kludge 2 infrared gas "screens" one in front of the other as some kind of "open oven" and hang the just powdered part in the middle for a couple minutes, it shouldnīt take more than that.

[ron vogel]

The eastwood company sells the same unit (costs more). They carry many more colors though.