Rusty transformers

[pucho812]

https://www.mercurymagnetics.com/transformer-rust-friend-or-foe/
Interesting

 

[mrclunk]

Very interesting, thanks.
I can't wait for the hifi crowd to get on board with this...
"All our transformers are hand oxidised in virgin glacial water, siphoned by blind nomads deep in the foothills of Everest."

 

[pucho812]

On one hand rust is bad especially in you using them in ham applications.  Rust does not shield well.

But on the other hand is the rust is cosmetic for audio seems to function without issue.

 

[rackmonkey]

I guess there’s also a threshold of “too much of a good thing”. Iron oxide is significantly less permeable than iron. If the rust penetrates deeper than just the surface of the laminations, it would lower the permeability of the core.

But it’s an interesting idea. First I’ve heard about surface rust reducing eddy currents. From experience, I’ve used a quite a few rusty transfoermers that sound great. Especially old Jensen JE-123-S in API circuits. Seems like just about every one of those Jensens from the 70s have a healthy layer of oxide on them.