The electro-galvanized steel is used in closed systems (i.e. without water), therefore there are no risks of electrolysis. Obviously, the "naked part" must be protected against external corrosion as more subject to corrosion compared to the electro-galvanized part.
FRABOPRESS 316 series is manufactured using AISI316L stainless steel whose resistance to corrosion is considered outstanding. Local pitting corrosion phenomena may happen in case of highly aggressive environments which should not be considered as a standard application. Generally strong corrosion phenomena are related only to exposure to environments where the chlorine local content or temperatures are way beyond the common thresholds.