Cheap steel - plated with black treatment...
I recommend building electric hubs with:
1. 2.3/2.0 Stainless Steel in 1X or 2X config depending upon how big or small the hub is.
OR
2. If drilled for it - 2.6mm straight guage - (105 guage) in 1X or 2X.
In some cases, interlacing will not be possible - that's okay though.
Keep in mind as well...that a lot of older electric hubs are getting dumped on the market...cause wheel build wise they were bad designs with nasty asymetrical flange offsets that on rear models resulted in spokes on one side not getting anywhere near enough tension. The companies had engineers - but not engineers familiar with workable flange offsets and the like.
Crystalite for example has addressed this in their latest disc brake and rear hub model line.
=8-)
__________________
5000+ wheels built since 1984...
Disclaimer:
1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:
Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life