Iron and steel are generally not a problem unless their mass is similar or smaller than that of the copper.
Copper stainless steel reaction.
The principal metals of concern in terms of direct contact are aluminum and zinc.
Corrosion issues with aluminum copper and stainless steel 2004.
However mixing these metals is not generally advised due to the potential for sudden pipe corrosion and discolored water.
If copper is connected to stainless steel type 304 then the copper will corrode to sacrifice to the stainless steel.
Lead and copper are quite close on the nobility table to stainless steel and so the bimetallic corrosion risks should be small.
There are three commonly used metals for potable water plumbing pipes including stainless steel copper and brass.
The elbows must be permanently joined to one frame member at each knock down joint.
Galvanic corrosion can be controlled by the use of sacrificial anodes isolation of the metals from electrical continuance protective plastic coatings or epoxy coatings or with corrosion inhibitors.
In most cases when stainless steel was in the passive state and acted as the cathode the contact accelerated copper corrosion.
These metals are used because of their durability and long lifespans.
Any corrosion product if washed onto stainless steel may however result in problems not associated with the bi metallic effect and so not be predicted from the tables.
In addition the area ratio of stainless steel to copper altered copper corrosion behavior.
I am constructing a project utilizing a knock down aluminum tube frame.