Chalky white residue on tube shields

[Neal]

Hey, Gents! Long time, no time!
I've been asked to go through a Silverface Fender Bassman head to make it gig-worthy after being stored for decades. I'll do the usual filter caps/grounded power cord/electrolytics thing. Something I haven't seen before, or at least quite this bad, is a chalky white residue coating the tube shields and the transformer end bells. This amp is spotless other than this chalky stuff. Any idea what caused this, and tips for cleaning?
Thanks in advance!

[J M Fahey]

Yes, it's a salt created on zinc plated parts after long time storage in a humid environment.

Zinc sacrifices itself (literally) to save actual iron below it; you have that white residue instead of ugly red iron oxide / rust pitting or eating through parts.

Wipe it with a wet cloth until you remove it all, discard the cloth because that salt is poisonous, if necessary dry parts with a hot air pistol, and, a personal favorite, I wipe surfaces with a cloth with a couple drops of oil so it has a minute protective cover.
Very light, you don't want it to be visibly oily and attract all lint floating around.

[Neal]

Thanks very much for the reply, Juan! Exactly what I needed!
Neal

[drewl]

I've seen it in several old amps, especially old stereo equipment.

[tedmich]

Zinc salt is poisonous.

Its also one of the main causes of anosmia, avoid zinc based cold remedies too!

[Neal]

Its also one of the main causes of anosmia, avoid zinc based cold remedies too!

I had to Google anosmia, and dang! I don't have much of a sense of smell! I always blamed it on sinus surgery I had when I was in my 20s, but now I'm wondering about all those old amps I tinkered on over the years....

[Mick Bailey]

Zinc oxide used to be used in lots of ointments and boil remedies. We get plenty of boils in the UK due to the smog and rain.

[Leo_Gnardo]

Zinc oxide used to be used in lots of ointments and boil remedies. We get plenty of boils in the UK due to the smog and rain.

And lifeguards used to paint their noses with it at beaches & pools. Maybe they still do, I don't much go to these places in recent years. Sure, I used to see it in skin ointments too, vitamins A & D and zinc oxide. So, what gives.

My sense of smell is 20/20. About the only sense that still works.

OTOH one of my customers had an unfortunate encounter with a skunk when he was 9 years old. He's had anosmia ever since. Curiously he took up smoking for a couple decades then finally quit when he realized he wasn't getting anything out of it. Another thing he didn't understand (many smokers don't) is cig smoke was making him smell bad. Sounds like a joke but it wasn't.

[eschertron]

...because that salt is poisonous

I received a '78-ish Champ from Ebay. There was that white powdery residue. Itchy. I had some sense and wiped it mostly off before I got it in my eyes, etc. I assumed the amp had been in a room (closet?) that had been bug-bombed, but I couldn't figure out how so much dust got into the chassis. Now I know what it was.

[tedmich]

And lifeguards used to paint their noses with it at beaches & pools. Maybe they still do.

Yes they do especially since it was recently shown that low levels of the two most popular sunblock chemicals are incredibly efficient at killing coral...
Makes me sad to think of all the Bullfrog death I spread while snorkeling those reefs in Kauai...

[TimmyP1955]

The same thing occurs on the matching transformer cover of a Hammond. Don't get that stuff in a cut - ouch!

[mozz]

If it's cadmium plating,its bad for your health.