Galvanic area effect/proximity

[duddini]

I have a general galvanic corrosion question, I'm early in the design phase so I have no firm details as yet. I know a large anode/small cathode is ideal, but in general will the anode corrode faster at the contact point with the anode (e.g. a steel housing with a Ti connector body) or will the low electrical resistance of the anode allow for a more uniform corrosion of the anode ?? My thoughts are there will be little or no difference, am I right ?

Thanks for any input.

"You can observe a lot just by watching"
Yogi Berra

 

[duddini]

Oops, I meant at the contact point with the cathode. Sorry for the poor proof reading.

"You can observe a lot just by watching"
Yogi Berra

 

[EdStainless]

I depends (I love saying that).
Are the two items connected? good contact? is there a seal or gasket?
What about the conductivity of the electrolyte?

In general there will be more attack next to the contact. If there is fluid under the connection then you are really screwed.

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[duddini]

Hedging your bets I see Actually I'm looking at threading a connector with a Ti body into a large 4130 steel housing, so the area ratio will be good. This will be sitting in ~600 meters of seawater, little or no current at that depth. I was initially thinking the area ratio would negate any dissimmilar metal corrosion problems of the steel, but I wanted some thoughts from folks who have some experience. It sounds like there will be more corrosion near the point of metal contact. Seems like I need to give this some more thought.

Thanks Ed

"You can observe a lot just by watching"
Yogi Berra

 

[mshimko]

The critical area will be in the threads, where there is essentially a 1:1 surface area ratio.

I wouldn't recommend a threaded connection.