Corrision

[Mr. Fixit]

I am getting ready to reinstall hardware on my Boom. I painted it.What should I use to eliminate or reduce corrosion (boom is aluminum). When I removed hardware there was quite a bit of corrosion around the screws and I decided to enlarge holes ,re-tap.Is there anything I can do to stop this corrosion?

[Talbot]

corrosion will be where stainless screws meet the alluminium. If possible, riveting with monel will eliminate corrosion, but if stainless/aluminium is essential, the try to provide a buffer layer - old inner tube for components, or proper corrosion paste designd for this purpose (dont know what its called in USA)

[GordMay]

Apply a good Anti-Seize compound to the male threads.
Anti-Seize Compounds are designed to protect threaded metal parts from rust, corrosion, galling and seizing. Good quality anti-seize has lots of metal (active ingredient) and little grease. This makes it thick and pasty. Since metal is expensive and grease is inexpensive, poor quality anti-seize is often a can of grease with a sprinkling of copper or nickle flakes. Zinc rich anti-seize is the best method of preventing corrosion seizing of SS threaded fasteners in Aluminum.

Separate the Aluminum Spar from the Hardware with an insulating Isolation Pad.

[Rick]

Several years ago Practical Sailor evaluated several common solutions to preventing the problem of S/S fasteners from interacting with the aluminum into which they are threaded. The best solution, at that time, was (oddly enough it might seem) Locktite. Use the kind which allows refitting unless you don't want to ever take out the fastener (then use the red stuff).

Since that time Ultra Tef Gel [ The Corrosion Eliminator and Anti-Sieze Lubricant] came along (expensive) and works well. What makes these very different solutions to work is their ability to prevent any egress of oxygen into the space separating the two materials under any condition.

I have successfully used 3-M mylar tapes to isolate S/S from the mast or boom using an Exacto knife to carefully form the proper outline of the part. Still working well after 26 years.

[Alan Wheeler]

I agree Rick, the blue locktite works very well. Also, Lanocote. I use lanocote a lot on all sorts of things. Hmmm, the smeel reminds of...something...???
Anyway, when you are fitting a component, firstly, use a urathane adhesive sealant by applying it is a thin film to one or both materials. Allow it to go off so as it is no longer sticky. Place a thin smear of lanocote to the surface and bolt up. If you want to add more strength than just the bolts or rivets, then apply both components while the adhesive is still wet and don't use the lanocote of course.

[DeepFrz]

Interesting, April Sail magazine has an article on re-fitting a mast. They say not to use rubber in between the fitting and the mast, but to use polyurethane like 3m 4200 or sikaflex 291. Use these for the screws as well. Lanocote, Tef-Gel, and Duralac can be used for removable items and fastener holes if wanted.