03-18-2020, 08:49 AM
Aluminum begins to form an oxide layer immediately on exposure to air, if it's not already present. This is what helps keep corrosion down.
Options:
1) Don't paint it. You don't need to - aluminum won't corrode outside of caustic environments (generally) anyhow.
2) Sand or brush the oxide layer off, wipe it down immediately with mineral spirit or denatured alcohol, and spray down as soon as it's dry with acid-etching primer (and you'll usually end up with an oxide layer anyhow.)
3) Anodise. Anodising is simply a special form of an oxide layer on the surface - it can be made to take a colour (many colours are available,) and you can make the oxide layer harder than the base metal (a MIL-spec hard anno on aluminum that has been mildly knurled will make a part that can be used to literally saw through an aluminum plate. Not sheet - plate!)
4) Powdercoat. Powdercoating isn't as hard as a good hard anno, and it's an applied finish (instead of a surface-layer conversion,) but it's stuck on better than most epoxy finishes.
I'd honestly say that option #3 is your best bet if a specific colour is desired, with #1 or #3 (clear anno) for metal "in the white." Powdercoating aluminum is reasonably effective, but anno is a better option.
Depending on the size of the parts and what means you have available, you can get anno or powdercoating kits to use at home. You can also fully DIY your anno setup with a little research. (Powdercoating requires heat, so you will be limited by the size of the oven you have available.)
Another option - if you need a muted colour - is an interesting PTFE/Moly finish that is available for use with firearms parts. I've seen it through Brownell's, and I've been wanting to get it for my refit to use on certain parts (mainly underbody stuff - brake calipers, backing plates, axle covers, and the like.) The colour selection may have expanded by now, and it's something that may bear looking into, depending on your needs.
Options:
1) Don't paint it. You don't need to - aluminum won't corrode outside of caustic environments (generally) anyhow.
2) Sand or brush the oxide layer off, wipe it down immediately with mineral spirit or denatured alcohol, and spray down as soon as it's dry with acid-etching primer (and you'll usually end up with an oxide layer anyhow.)
3) Anodise. Anodising is simply a special form of an oxide layer on the surface - it can be made to take a colour (many colours are available,) and you can make the oxide layer harder than the base metal (a MIL-spec hard anno on aluminum that has been mildly knurled will make a part that can be used to literally saw through an aluminum plate. Not sheet - plate!)
4) Powdercoat. Powdercoating isn't as hard as a good hard anno, and it's an applied finish (instead of a surface-layer conversion,) but it's stuck on better than most epoxy finishes.
I'd honestly say that option #3 is your best bet if a specific colour is desired, with #1 or #3 (clear anno) for metal "in the white." Powdercoating aluminum is reasonably effective, but anno is a better option.
Depending on the size of the parts and what means you have available, you can get anno or powdercoating kits to use at home. You can also fully DIY your anno setup with a little research. (Powdercoating requires heat, so you will be limited by the size of the oven you have available.)
Another option - if you need a muted colour - is an interesting PTFE/Moly finish that is available for use with firearms parts. I've seen it through Brownell's, and I've been wanting to get it for my refit to use on certain parts (mainly underbody stuff - brake calipers, backing plates, axle covers, and the like.) The colour selection may have expanded by now, and it's something that may bear looking into, depending on your needs.