Galvanic Corrosion
Galvanic Corrosion
(OP)
Two metals that form a galvanic couple (brass and 304 stainless steel for example) are immersed in salt water and near eachother (approx 1 foot apart), but not touching.
Will the brass corrode? Is the salt water enough of an electrical conduction path to create galvanic corrosion?
Thanks for the help!
Will the brass corrode? Is the salt water enough of an electrical conduction path to create galvanic corrosion?
Thanks for the help!





RE: Galvanic Corrosion
Heckler
Sr. Mechanical Engineer
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RE: Galvanic Corrosion
Concentration gradients in the electrolyte could lead to some corrosion in some cases.
RE: Galvanic Corrosion
See if this helps,
RE: Galvanic Corrosion
These are the requirements for galvanic corrosion:
- anode and cathode
- thermodynamic tendency for a reaction to occur ("delta G < 0)
- contact with a common electrolyte
- external electrical connection (I've seen this last requirement described many ways; I find it useful to think of a "wire or wire equivalent" connecting the anode and cathode)
Take away any of these, and there will be no galvanic corrosion.
RE: Galvanic Corrosion
I'd express it as there is no flow of electrons between the atoms of the constitutent metals when the alloy is sitting on the bench. The salt water doesn't really factor into the problem (the alloyed elements are sufficiently close contact to allow electrons to flow if they wanted to). But the salt water, being corrosive, will probably corrode the brass.
RE: Galvanic Corrosion
2) If brass & SS are in a closed system, the SS may move from a passive to an active state of corrosion due to the presence of dissolved Cu & Zn ions along with the Cl of seawater.
RE: Galvanic Corrosion
Considering the two metals separately in salty water they will both corrode because they are not pure homogeneous materials each material by itself will have cathode and anodic areas so corrosion will occur corroding anodic areas.
As both metals are close together but not touching each other, chloride ions of salty water will be more prone for SS than for brass. I would forecast severe pitting end chloride SCC for SS304 and dezincification for brass.
luis