Stainless steel against galvanized steel

It is a common practice that in every junction between stainless steel and a galvanized steel to put a separator or corrosion inhibitor. Now I want to know where this specification came from and what is the corrosive effects when will join together without separator. In view of this matter we are installing a stainless cable tray with a galvanized supports and galvanized cable tray connecting to stainless cable tray. This is a hazardous and non-hazardous location in an industrial plant.

Thank you very much if you can give me a clear answer on this subject.

Dear Friend,
I am not much familiar about your question, but I would like to share that galvanized steel has zinc and stainless steel has chrome. Generally if you join two dissimilar metals a potential difference will exist between them, and if this potential difference exceeds the corrosion potential then rusting takes place. In your case the galvanized steel will have more electro negative potential than the stainless steel and galvanised starts rusting at a faster rate than it would have had when exposed alone.

Hope that would have cleared your cleared your doubt.

Regards