Corrosion on Hx at anode - ideas?

[KWKloeber]

A cross-post from a C-30 owner w/ a problem.  I hope if someone has experienced this and determined the cause at this specific location they will chime in.

We purchased this 3 inch heat exchanger about four years ago and it's worked wonders on our engine heating issues. We periodically check and replace zincs in the heat exchanger. But there's a growing amount of corrosion around the nipple for the zinc threads. I'm wondering if others have seen this happen, and believing I need to change that soon or else I'm gonna have a leak?
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[scgunner]

Mine does the same thing and also around the end caps, but doesn't leak. I'm on my third heat exchanger and they've all done the same thing. I've tried a number of fixes including new gaskets, clamps, hoses, gasket sealer with no luck. My thinking is since I have no leaks that possibly during the heating/cooling cycle atmospheric moisture condenses on these places allowing the corrosion. That's a guess of course, I have no facts to back that up, but since it doesn't leak I don't spend a lot of time worrying about it. From time to time I pull it off, clean, repaint it, and replace it and call it good.

[Ron Hill]

Ken : There is a leak there somewhere - as the salt water is corroding it!!  To stop the corrosion I'd clean it up and put some grease in that area. Grease will not plug the leak, but it will stop the corrosion.

A thought