What sealant (or other) to use for this?

SFS

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Aug 18, 2015
2,066
Currently Boatless Okinawa
I'm reinstalling a cleat ripped out during Irma. The cleat is aluminum, fasteners are 316 stainless. I want to isolate the fasteners from the cleat. Hunter did a great job on the original fasteners, as there was some sort of white caulk-ish substance between the fastener head and the cleat. That same material was all the way down the body of the bolt, around the threads, inside the nut, and all over the washer. I would use it if I knew what it was. It held up for 30 years, and there was no galling between the two dissimilar metals.

What would you use to prevent galling, and to seal this properly?
 
Mar 26, 2011
3,402
Corsair F-24 MK I Deale, MD
Galling and sealing are two different things.

The sealant was one of many polyurethane sealants, probably from 3M or Sika. As for the threads, Tefgel is probably best.

As a practical matter, your going to get sealant on the threads. It works too.
 
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Apr 22, 2011
865
Hunter 27 Pecan Grove, Oriental, NC
Are you sure that the "white caulk-ish substance" is not aluminum oxide from the cleat. The buildup of oxide protects the cleat from further corrosion.
 

SFS

.
Aug 18, 2015
2,066
Currently Boatless Okinawa
No, I know aluminum oxide. This was a rubbery sealant that I peeled off.

@thinwater - do you have any suggestions as to a specific modern product? Technology has changed since 1983.
 
Mar 26, 2011
3,402
Corsair F-24 MK I Deale, MD
No, I know aluminum oxide. This was a rubbery sealant that I peeled off.

@thinwater - do you have any suggestions as to a specific modern product? Technology has changed since 1983.
Sika 291, 3M 4200 UV, and Loctite Marine are all of a very close par. Sika is a chandlery item, but Home Depot generally caries the latter two. Seal the excess in the tube, put the tube in a freezer bag, and put the lot in the fridge if you can. In this way it will last ~ 1 year. Otherwise it will tend to go off after opening in a month or so due to humidity.
 
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SFS

.
Aug 18, 2015
2,066
Currently Boatless Okinawa
Thank you kind sir. I will probably use the Locktite product. A google search for the 4000UV took me to a couple of posts on The Hull Truth about formulation issues for that product at 3M several years ago. I assume they would have figured that out by now, but I don't find any locally (just 4200), so the locktite is easy at Home Depot.
 
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