Coated aluminum corrosion in seawater pump application
Coated aluminum corrosion in seawater pump application
(OP)
I know the basics about electrolysis and how it corrodes aluminum in salt water. Heres my question though.
In a sea water pump application were no electrical current is present, if a coated aluminum housing is used, will the aluminum still corrode due to electrolysis. I'm told that any contact of aluminum with dissimilar metals, even in the non wetted part of the pump, will cause electrolysis. Is this true?
In a sea water pump application were no electrical current is present, if a coated aluminum housing is used, will the aluminum still corrode due to electrolysis. I'm told that any contact of aluminum with dissimilar metals, even in the non wetted part of the pump, will cause electrolysis. Is this true?





RE: Coated aluminum corrosion in seawater pump application
The dissimilar metals plus electrolyte comprise a battery cell, and will produce a current of their own with no external assistance.
Mike Halloran
Pembroke Pines, FL, USA
RE: Coated aluminum corrosion in seawater pump application
the aluminium coated surface is in contact with seawater?
where do the galvanic corrosion came from, i mean what is the other material?
S
Corrosion Prevention & Corrosion Control
RE: Coated aluminum corrosion in seawater pump application
But that wasn't your question. You asked about dissimilar metals in contact with the aluminum, on the dry side of the pump.
Where seawater is involved, there _is_ no dry side of the pump. The pump will eventually develop a leak, and the seawater will find its way to the metal-metal interface.
Mike Halloran
Pembroke Pines, FL, USA
RE: Coated aluminum corrosion in seawater pump application
Thanks,
Tryg Waterhouse
RE: Coated aluminum corrosion in seawater pump application
Old salts would say the electrolyte will be there.
The pump doesn't understand the theory.
Don't assume the aluminum will be the metal attacked, either.
Mike Halloran
Pembroke Pines, FL, USA
RE: Coated aluminum corrosion in seawater pump application
Thanks a lot for the information. It sounds like its worth at least prototyping and testing.
Tryg Waterhouse
RE: Coated aluminum corrosion in seawater pump application
I have seen a bronze ship side valve with steel stud bolts holding the bonnet, totally eaten away. Nearly lost the ship because of it. The studs just wasted away. The valve was nicely painted so the dissimilar metal was not apparent. The studs had no direct contact with sea water either.
Aluminum in sea water is not a good idea and has a short lifespan,especially if you use steel bolts.
The old DC3(Dakota) aero engine had an aluminum engine block. Old hands will tell that the steel bolts kept stripping out of the block, and these engines were air cooled.
Offshore Engineering&Design