aluminum & galvanized steel

[PaulLag]

Hello

Hope everybody is fine.
Please I’d like to ask you an opinion about following concern

I have an aluminum tube coupled with a galvanized steel end plate.
The area of contact is of 1mm ca.
This assembly undergoes a combined swat (therefore Solphures) and salty fog test (therefore Chlorides)

My concern is as follows.
At beginning, zinc is less noble than aluminum. Meaning what will corrode is zinc.
After the zinc has gone, the iron is more noble than aluminum.
Will then the aluminum corrode ?

Please, can anybody tell me if my concern is justified ?

Thanks and Happy holidays to you and all your families

 

[cap1a79]

Yes, correct.

Aluminum will corrode as it is more active than steel. Note that aluminium is one of the materials used for sacrificial anode.

One more thing to note is that although zinc is more active than aluminium generally (ex., galvanic series), however, sometimes aluminium is more active than zinc depending on alloying element or passivation trend against environment. Anyway, if you are just asking whether the material that will corrode between the two (cs vs al) is aluminium or not..yes aluminium will corrode and steel will be the last one.


Lee SiHyoung,
Engineer - Material & Corrosion Specialist
WorleyParsons Oman Engineering,
cap1a79@gmail.com