HV Battery terminal nuts - what metal?

Hello everyone - i have a mystery no amount of googling seems to help:

What is the metal and coating for the 56 nuts on the HV battery cell terminals? these nuts - which look like average metal with a clear/semi-shiny, coating, hold the copper bus bars against the terminals, within the orange 'strap' on both sides of the traction battery.

I took my battery apart to removed corrosion (it worked! much better performance now!). The copper buses were highly corroded with black, so i soaked them in vinegar. I also threw in the nuts.

And the nuts turned COMPLETELY BLACK!

And as i've tried to wash and clean them, they are obvoiously now beginning to corrode when wet. I'm sure i stripped off the coating.

So what are these nuts? Brass? Steel? Coated in zinc? Cadmium? They are not part of the system's current path, so I don't know.

they are toyota part #: G9291-47011 (they are 5mm, flanged, ie broader at bottom, like a 'built in' washer)

But what are they, and more to the point, any engineers care to say what would be a good material/coating for an HV system?

Thanks!

 

thanks so much for this link. you should ask that guy for a finders fee.

for some reason i wasn't searching properly on ebay. Toyota dealer wanted 1.20 per nut, other outlets at least 75c per.

i guessed cadmium. I've read where vinegar (ie acid) was exactly the wrong thing to put them in (it was the right thing to put the copper bars btw). Ive seen some welding forums where guys are talking about stripping coatings off metal in order to weld it, and vinegar is a favorite.

lesson learned for sure.

RESULTS btw: after clean all corrosion off bars and terminals (particuarly the copper bus bars), battery is now holding charge much better and im seeing 'all green' on the indicator up front during driving. haven't seen that in 6 months or so. even when it dips down - and i would say the battery is still dipping below 1/2 more often than a new one would - it comes back quickly.

thanks again