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Sailboat Owner's Guide to Corrosion - Protection (Collier 13 - 15, 18)

Oct 19, 2017
6,014
O'Day 19 Littleton, NH
Collier has a fair amount to say about plastics and elastomers (new word for me, natural and synthetic rubbers/neoprene).
He talking about electrical insulators. These materials can be used to prevent an electrical connection between two dissimilar metals.
Thermoplastics are non-cross-linked polymer chains and get soft when heated at relatively low temperatures. These include polyethylene, polystyrene, polypropylene, nylon, PVC and some polyurethanes.
Thermo setting plastics are cross-linked polymer chains and more rigid than thermoplastics. They include epoxy, polyester, silicone, some polyurethanes and rubber.
Plastics can be hygroscopic, meaning they absorb water. This can change them by making then softer and can cause them to swell.
For the most part, however, natural waters, those we find while boating, have little effect and are used for all sorts of things on boats.

The next chapter, 15, covers coatings as electrical insulators for metal parts.

-Will (Dragonfly)
 
Oct 19, 2017
6,014
O'Day 19 Littleton, NH
I wrote, Collier covered coatings as electrical insulators for metal parts, but that's not a complete picture. The first part of the chapter is on metallic coatings. They can act either as or both as electronic insulators, removing contact with the electrolytic, and as sacrificial anodes.
When I first took my pock marked centerboard out of Dragonfly, I thought I might want to coat the cast iron in lead. Smooth out the surface and add a bit more stiffness to her righting abilities. Not being familiar with the process, I opted to go simple and use just a high build epoxy-based barrier coat.

It seems the lead might have been an excellent choice. Lead has a very high resistance to corrosion and it would have isolated the iron very well. I would have still painted it with a barrier coat to protect the lead from physical damage.

All other coatings, Collier pumps in under "Organic Coatings". He has some very interpretation things to say about all of them. The chapter is a great resource for information on different coating options availible. As far as the applicability to corrosion protection, the basic concepts are fairly simple. For features like adhesion, ease of application, air/water permeability, and other stuff, it's worth a read. He tells you a little about their composition, where they are generally used and for what. There's a lot here, even as a general survey of what coatings are availible.

-Will (Dragonfly)
 

dLj

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Mar 23, 2017
1,047
Hunter 30 Snug Harbor, Lake Champlain
Coatings is a huge and very dynamic field. One of the recent NACE publications shows lots of chatter about coatings...


Your lead would have worked. I think it's been outlawed since 1978, at least lead paint use in homes has been. I used to buy a primer that was essentially loaded with lead that you painted on the exposed steel and then did a top coat once dried. I can't remember the name of that primer. Worked very well, but sure was not fun to work with for recoating...

There is a lot of research being done in organic coatings. There are some amazing coatings out there.

dj
 
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