white residue on metal film holders

[spoolman]

I picked up about a half dozen all metal 3x4 film holders made by Alkon.I'm not sure how to clean off this white residue that is on and inside each holder. I have had a very difficult time trying to remove the dark slides and I've broken a couple trying to get them out.

Any advice as to how to clean the residue off and make them usable again would be appreciated. Images are attached.

Doug

 

[AgX]

This is metal corrosion at Zink or Aluminium. Only remedy would be grinding...

I likely would toss them.

 

[Donald Qualls]

Given the relative scarcity of usable plate holders with film sheaths inside in that format, I probably wouldn't toss them without trying to clean them up first. I'd start with a stiff wire brush.

You're almost certain to knock off a significant amount of paint, so first remove the film sheaths (with them, you'd use standard cut film, without you can order dry plates from J. Lane, who is a member here). Get the white stuff down to bare metal, apply a zinc chromate primer for metal, and then paint with a matte enamel to (fairly well) match the original black.

 

[AgX]

Problem is that as they look outside, they likely look inside too. Working on the inside, within the recesses would need custom tools. And a lot of trouble. Then it depends whether the rarity is worth the effort.

I guess the OP hoped to dip them into some potion and off goes the incrustation.
(Some peole say they got such for at least rust, but even that did not work that miraculously to my experience.)

 

[Nodda Duma]

If aluminum, sand down the corrosion and re-blacken with a Birchwood Casey Aluminum Black pen (google it). Good luck!

 

[Alex Varas]

I cleaned a couple of MPP 4x5 plate holders from that dust. The outside was wood and the dust was present in the metal parts, I was lucky these holders can be unscrewed for replacing the light trap and there is where I found most of the issue, after grinding the main rust and replacing the light traps the dark slide was working smoothly and the inside was clean.
That pen mentioned above works well.

 

[reddesert]

Alkon holders are made of aluminum. The white stuff is aluminum oxide. You can try cleaning it off with vinegar and an abrasive like steel wool, or maybe very fine sandpaper (the paper for wet sanding). I've cleaned some film holders off this way, but I haven't used them yet. If you use steel wool, you'll want to clean very thoroughly to get the loose wool threads out afterwards.

 

[spoolman]

Alkon holders are made of aluminum. The white stuff is aluminum oxide. You can try cleaning it off with vinegar and an abrasive like steel wool, or maybe very fine sandpaper (the paper for wet sanding). I've cleaned some film holders off this way, but I haven't used them yet. If you use steel wool, you'll want to clean very thoroughly to get the loose wool threads out afterwards.

Hi reddesert: thanks for the info. I've already tried vinegar with little success. I'm going to use a wire wheel in a moto tool then either a grinding wheel or a carbide bit to get rid of the exterior rough spots. I might try the wet sanding paper to clean out the interior spaces where the dark slide goes and see what it does.

Doug