Aluminum and Plastic Reaction

[vdi_nenna]

I place a DVD case with a clear plastic sheath on a bare aluminum "Bud" box. When I removed the DVD case, there was an imprint on the case in the aluminum. I also saw this happen when I place a plastic ear bud used for ear protection on aluminum over night.

Can this happen with internal wiring like PVC or Teflon?

I'm worried about desolving a power cable and causing electricution or fire.

Any thoughts?

Thanks,

Vince

 

[Cal Weldon]

Vince,

Was this something to do with heat maybe?

 

[vdi_nenna]

Hi Cal,

Well, maybe. The aluminum enclosure contained my Bride of Zen preamp. It doesn't get very hot, just warm. This is definately a reaction. It seems to happen with soft plastics. I'm just concerned it will happen with the wiring of a project.

I'll try to take a picture.

Thanks,

Vince

 

[Cal Weldon]

Sounds like that might be it. I've not heard of that kind of reaction before. Can you remove the plastic stain with a dry sugar cube?

 

[vdi_nenna]

I don't have suger cubes, but I can get some. Do you think this will tell us something if it comes out with sugar?

 

[Techlab]

I belive the "Bud" cast enclosures are not aluminium at all, but Zinc. I may be wrong, and they may be an alloy, but I'm pretty sure they are zinc. The polycarbonate resin that CD's are moulded from is highly modified, but none of the additives should reat with the zinc. At least not quickly.

 

[jacco vermeulen]

Any thoughts?

Whenever i cover something metal with plastic there's moisture between the two within an hour.
(Could be because i'm a swamp resident)

 

[vdi_nenna]

I belive the "Bud" cast enclosures are not aluminium at all, but Zinc.

Zinc huh? They lied to me! Just kidding, they're nice for the price.

It's actually a Hammond box. I forgot. It says, "aluminum".

The item at the top of the PDF.

http://www.mouser.com/catalog/630/1581.pdf

I'm going to run a test tonight and take a photo or two.

 

[TwoSpoons]

I think all you are seeing is the plasticiser leaching out of the plastic. Aluminium is always coated with a highly inert oxide layer, so I sincerely doubt you are getting a 'reaction'.

 

[Nordic]

If it realy bothers you, get thermal material remover from a PC shop.... like ArctiClean. Comes in 2 little bottles... one to remove goo... and one to 'purify the surface afterwards....

Has a very strong smell of citrus, so maybe the oil from an orange peel might also work.... did you know it is inflammable... squeeze an orange skin into the flame of a lighter...

 

[vdi_nenna]

I ran a test and couldn't recreate it. It was probably trapped air between the plastic and aluminum that condensed and stained.

thanks for the help!

Vince

 

[neutron7]

was the al fairly new and non anodized? it will oxidize with anything it can find. once it has been sitting for a while and had a chance to oxidize with the atmosphere that is less likely to happen unless there is some bad chemicals in the plastic.

 

[wrenchone]

To VDJ - die casting alloys incorporate some zinc along with the aluminum to make the stuff easier to mash into shape. There's probably a few other goodies in the mix as well. This also makes the resulting alloy easier to drill, not like the usual gooey aluminum. Loading a search engime with "die casting alloys" would probably result in more information than one could ever want....

 

[vdi_nenna]

was the al fairly new and non anodized?

Yes, it was. It came covered with a plastic film, shiney like a new dime.