8mm Forum: Gray powder in old projector

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Posted by Thor Simpson (Member # 3453) on January 05, 2013, 12:28 PM:

I've bought and old Eumig 610D (on eBay) and it arrived beautifully packed. But there is a light gray powder over many interior surfaces. It does not vacume off but a power toothbrush moves it. Before I risk breathing in or speading too much of it around, can anyone suggest what it is and what caused it?

Thanks

Posted by Steve Klare (Member # 12) on January 05, 2013, 03:52 PM:

It looks like aluminum oxide.

Does a magnet stick to the parts affected by it?

Posted by Graham Ritchie (Member # 559) on January 05, 2013, 04:39 PM:

I think you will need to try to remove as much of the surface corrosion as possible and treat "whats left" of the remaining material, if its possible. It looks really bad and could have been caused by salt in the air, dampness, anything, or the material was simply of poor quality with little or no resistance to corrosion to begin with.

If you do give it a go, as well as treating the remaining material, I think you will have to seal it with some sort of anti-corrosive paint as well, that should keep the air "oxygen" away from it.

best of luck

Graham.

Posted by Pasquale DAlessio (Member # 2052) on January 05, 2013, 05:05 PM:

Graham is right. Use a vaccum cleaner with the brush attachment. Then seal it with automotive zinc oxcide primer. Then your good to go. [Wink]

Posted by Thor Simpson (Member # 3453) on January 06, 2013, 11:53 AM:

Thank you all. Magnet test - its non magnetic.

Have removed one part and left it overnight in coke and its cleaned up quite well.

Need the full service manual before I risk disassembling the rest.

Posted by Steve Klare (Member # 12) on January 06, 2013, 12:58 PM:

Thor, it looks like you've struck "aluminium"!

The oxide is not dangerous, and Graham is right: it's likely the result of the environment the projector was kept in.

In a lot of cases I'd say just ignore it, but little flecks can cause major mayhem inside a movie projector.

Maybe after you clean the effected parts a spray of acrylic clear will prevent it's return and preserve a normal appearance where it's visible.

Posted by Paul Adsett (Member # 25) on January 06, 2013, 02:06 PM:

Any exposed Aluminum alloy (Al) will naturally oxidize to aluminum oxide (Al2O3). Humidity and moisture will really accelerate this process. There are two solutions that manufacturers can use to prevent this. The first, which is very inepensive, is to dip the parts in a Zinc Chromate bath. This process is called 'Irridite' or zinc chromate conversion coating, and puts a nice yellow protective coating on the surface of the aluminum, which also makes it ideal for painting. This is required procedure for use of aluminum on military equipment, and its very suprising that Eumig did not use it, as it is really cheap. The second process is electrical anodizing, which puts a very hard resistant coating on the Aluminum , and you can get just about any beautiful color you want - but it is expensive.

Posted by Thor Simpson (Member # 3453) on January 06, 2013, 02:17 PM:

Steve, I think its concern about the stray particles when running a film that have me making the effort to clean it all.

Graham, Paul, Thanks. Its an eBay purchase and as I want to "reconfigure" it I didn't ask about condition , just did it run.
I do not know when the 610D was in production but I suspect this one has just languished in some attic for many years.

Paul Have you tried making a "Zinc Chromate bath" or are we in laboratory stuff her?

Regards Thor

Posted by Lee Mannering (Member # 728) on January 06, 2013, 02:31 PM:

1/ Take it outside and with a soft brush it will come off.
2/ Put some WD40 on a cloth and rub it over the alloy.
3/ It will then be good as new.
4/ Enjoy your Eumig!

Posted by Paul Adsett (Member # 25) on January 06, 2013, 07:02 PM:

Thor, I believe the zinc chromate conversion process bath uses some chromic acid, which is really nasty stuff. One of those things that only the professional metal finishing companies should be messing with. EPA, OSHA, etc is involved.
I would say that if you are going to strip this projector right down to the bare aluminum chassis, that a plating house would do a far better job of cleaning off the old oxide than you can possibly achieve. Once they have it stripped, it would cost you very little to have the chassis subjected to the zinc chromate process, as any good plating house will be doing this process on a daily basis and will have the tank all set to go.

Posted by Thor Simpson (Member # 3453) on January 07, 2013, 12:18 PM:

Lee , I will give that a try, but its so extensive I'm leaning towards Paul's suggestion and looking round for a company that can do it.

Thanks both.

Thor

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