Best Way To Clean Off Green Powder Dust Off Old Chassis?

[Jecarroll7]

Bring back to life a few old organ amps I've noticed the chassis and speakers are covered in a pale green powder. I've bumped into this again bringing an old Grundig speaker amp back to life. The dust only clings to the metal parts, inside and out.

What is it? And what is the best way to clean it off?

[Mick Bailey]

Nickel will turn powdery green if damp, but cadmium was used to plate chassis and components on a lot on older equipment. Is it strongly adhered?

Good idea not to breathe it in or vacuum it. Some of this stuff from the 60s interferes with the area of the brain known as 'Shatner's Bassoon'

[Jecarroll7]

Tried to upload a photo, but the site upload feature doesn't seem to work.

The powder builds up in layers on the metal. If you touch it, it does come off on your finger. I used contact cleaner on the piece in the photo thinking wet dust is better than dry dust. That got the loose powder off but I then had to polish it as it left stubborn green stains.

I'm guessing this has something to do with the chassis having a charge?

[Enzo]

I never knew what it was, I always THOUGHT the chassis might have been galvanized and the green stuff was breakdown of a zinc compound.

[J M Fahey]

^^^^^^ That's about it.
Nickel/Chrome protect metal by making a barrier against oxygen, but in any nick/scratch/pore rust will happily set in and "eat" the iron below the surface, same as happens with paint.
Zinc plating/galvanizing on the contrary, "sacrifices" itself (literally) to save iron from oxidation.
Instead of becoming an orange hulk, zinc plated chassis show a white dust appear along time, and it will not rust until all zinc is "eaten".
Cadmium plating works in a similar way, but starts yellowish/orange so you probably are seeing its decay.

Only real treatment is stripping and replating the chassis, but when not feasible (most cases) , spray some WD40 on it, let it work overnight and wipe clean next day.
Ugly but serviceable.
Do not degrease it, a very light oil film remaining (whatever stays after wiping with clean tissue paper) is fine and helps.
Repeat once a year.

[J M Fahey]

No longer needed.
Thanks Steve

[Steve Conner]

By way of explanation, I deleted the offending spam post and banned the user. JM is not accusing himself of being a stinky spambot.

[J M Fahey]

Ain't I ?