i have 1000's of mild steel and expanded metal parts plated every year.
the zinc plating lasts for some time and our products
and they are abraided in the field with sand and gravel....
black or mild steel has more flex than C.R. and will cause the plating to fail over time.
find a different plater!!!
I use
commercial electro plating in Calif.
http://www.commercialelectroplating.com/