White dust at screws at portholes?

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Oct 7, 2007
Vessel Make
Bayliner 4550 Pilothouse
So this bay' 45 I am looking at....I noticed today she has at some of her portlights a while chalky power/residue coming off the screws at the bottom of each frame and enough to where it is going down the sidewall headliner. *Strange. *Anyone seen it before? *I assume oxidized/corrosion of the screws? *Was a salt water boat but she has been in fresh since 2007! *

I gotta say- I love the space of the 45 but it sure reinforces to me how awesome my Monk is! *I was making my project list today before we do the survey and found myself pondering if I had the energy to do back to back refits along with everything else I have going on. *:)

Crazy me!! *
Probably aluminum oxide. *Kind of hard to avoid when you use stainless screws into aluminum.*
frames are definitely aluminum. What's the fix? Change screw types?
The problem is the contact between the SS and Al.

You might remove the trim ring paint it under the screw holes.

Or find/create thin non conducting washers for under the screw heads.
Try a product like Tef Gel. It is made to prevent corrosion between SS fasteners and AL.
Thanks Rick * *......did'nt know about that. *How does it come *...in a tube?
Won't a layer of anti-seize compound do the same thing?
nomadwilly wrote:
Thanks Rick * *......did'nt know about that. *How does it come *...in a tube?
ditto......Same question.
Hi Woodsong: They make plastic washers for that type application.Check with a major Marine Supplier or Mac master Carr
Try Duralac.* We have*used it for*10 plus years with good*results.** Here's some cut and*past info and the link from the manufacter.* Hamilton Marine in Boston now sells the stuff.
Used in the Aerospace industry as an essential corrosion inhibiting material wherever dissimilar material are used.* Duralac is an anti-corrosive jointing compound for use between joints of dissimilar metals.
Properties Barium chromate is only very slightly soluble in water and hence is not leached out of the joint even in the presence of a considerable flow of water. It is tough and flexible, absorbs little water and is resilient to seawater.
Uses Duralac is indispensable for the sealing of joints between dissimilar metals of all types including magnesium and its alloys.



-- Edited by Larry M on Thursday 13th of October 2011 05:42:42 PM
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