Cast iron gates not recommended for stainless steel extractors?

[D Coates]

While reviewing a few supply sites I noticed that the extractors don't come with gates.  Fine, I guess that's extra.  The when I look up gates there are plenty of gates but the cast iron ones that look like they should go with the extractors have the caviet of "not recommended for use on regular stainless steel honey storage or extractor tanks.  I am assuming this is due to metal reactivity.  What actually happens in this reactivity pairing?  Also, with this said what gates are recommended for use on/with stainless steel extractors?

[backyard warrior]

i think plastic

[WPG]

The acidity of the honey will react with all other metals and the honey will darken and eventually turn black.

So it's either SS or plastic.