Thanks all. Sounds like zinc plating it is. No need to SEM, but thanks for that offer. My spokes overall are in good shape. Dirty, yes and some have light surface rust. I unlaced both front and rear today. Will spend a bit of time on them with a some of the tips from here.
1) D40 and 0000 steel wool, light pressure
2) Coke (with or without) the aid of lubricants for the worker (me)
3) CLR or Neverdull
Have a lot of other stuff to do, so spokes will be last. If I am sick and tired and dirty from hours of other polishing, then SS spokes will be the order of the day.