Galvanic corrosion
02-04-2016, 01:07 AM
#1
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Galvanic corrosion
Any scientists here? I'm having a hard time deciding which is better:
A tiny brass pipe plug(cathode) in the relatively large aluminum(anode) intake manifold.
A tiny zinc plated pipe plug(anode) in the relatively large aluminum(cathode) intake manifold, but the 2 materials are very close in the galvanic series.
Keep in mind the crankcase PCV vapors(gasoline/oil/water) flowing past one end of the plug may act as electrolyte. I'm leaning towards the brass, but would appreciate verification.
A tiny brass pipe plug(cathode) in the relatively large aluminum(anode) intake manifold.
A tiny zinc plated pipe plug(anode) in the relatively large aluminum(cathode) intake manifold, but the 2 materials are very close in the galvanic series.
Keep in mind the crankcase PCV vapors(gasoline/oil/water) flowing past one end of the plug may act as electrolyte. I'm leaning towards the brass, but would appreciate verification.
02-04-2016, 01:24 AM
#2
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According to "Mil-STD-889", a brass plug in an aluminum part is a very big "No No".
Click the link below for the appropriate PDF files on Galvavic Corrision between dissimilar metals as conducted by the military.
ASSIST-QuickSearch Document Details
Click the link below for the appropriate PDF files on Galvavic Corrision between dissimilar metals as conducted by the military.
ASSIST-QuickSearch Document Details
02-04-2016, 10:43 AM
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Yes, tape would help insulate the electrodes, reducing or retarding galvanic corrosion. But it seems neither brass nor zinc is a good material for this application.
Although table 1 indicates that zinc and aluminum are compatible, the small anode(zinc) in the large cathode(aluminum) is to be avoided. Once the zinc plating corrodes galvanically, then the underlying steel would corrode normally.
Conversely, table 1 indicates brass and aluminum are incompatible. However, the small cathode(brass) in the large anode(aluminum) causes little galvanic corrosion, and even if the aluminum does start to corrode, would that form a protective layer of aluminum oxide, halting corrosion? Or perhaps since the two threaded surfaces are sealed together, oxygen is not present there, and aluminum oxide would not readily form?
I think I'll try to find an aluminum pipe plug. Thanks guys!
Although table 1 indicates that zinc and aluminum are compatible, the small anode(zinc) in the large cathode(aluminum) is to be avoided. Once the zinc plating corrodes galvanically, then the underlying steel would corrode normally.
Conversely, table 1 indicates brass and aluminum are incompatible. However, the small cathode(brass) in the large anode(aluminum) causes little galvanic corrosion, and even if the aluminum does start to corrode, would that form a protective layer of aluminum oxide, halting corrosion? Or perhaps since the two threaded surfaces are sealed together, oxygen is not present there, and aluminum oxide would not readily form?
I think I'll try to find an aluminum pipe plug. Thanks guys!
Last edited by RJ_RS_SS_350; 07-05-2017 at 08:31 PM.
02-04-2016, 10:48 AM
#7
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The 2.0 uses an aluminum intake manifold. I'm working on a catch can setup like Dbeluscak, I'm relocating the PCV valve to the exterior of the manifold, and I need to plug the orifice where it was originally located.
02-04-2016, 10:50 AM
#8
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Blue the SS has an aluminum intake manifold. Wouldn't want all that boost in plastic! Just to clear things up.
-RJ is quick on the responses!
And wow! That's a good thought,RJ. I used a good RTV sealant paste on the threads. My plug is zinc coated.
-RJ is quick on the responses!
And wow! That's a good thought,RJ. I used a good RTV sealant paste on the threads. My plug is zinc coated.
02-04-2016, 10:58 AM
#9
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Yes, I was going to use the zinc one, but decided I'd rather have a set screw type, which at the hardware store is brass. The barb fitting I have for exiting the intake manifold is brass also, so I'll get that in aluminum, too.