The main component of an Alloy boom is Aluminum, and Al forms a layer of oxide on the surface of the metal. The oxide coat is impermeable to O2 and H20 so that protects the boom from rust.. The bolts should be stainless steel so shouldn't rust either.. But a dunk in fresh water would help get sand and stuff out.. It's windsurfing that weakens Alloy booms

*Edit, Haircut is right again.. I always thought it was the rubbing off of the oxide.. Another reason to buy carbon!..
http://www.corrosionist.com/stainless_steel_aluminum_galvanic_corrosion.html

I may very well be wrong here as it's been a long time since I've paid any attention to this, but...

Galvanic corrosion will be worse if you stick the two dissimilar metals in an electrolyte, basically what you are doing dunking the head in a tub of water (with salt). Without an electrolyte it will proceed a lot more slowly (or not at all?). Yes the aluminium will form a surface oxide which will act as a barrier, but every time you sail this oxide barrier will probably get broken, then reform.

Big picture thou, I think most decent booms these days tend not to fail in the connections these days as the connections are fairly over engineered. And if its got a monocoque front end, there are no dissimilar metal interfaces to worry about. As barn mentioned above its more likely the arms will fail windsurfing due to fatigue.

Problem with alluminium booms is they are made of an alluminium alloy not pure ally. The ally is mixed with things like copper and zinc to make it stronger/stiffer but this also reduces its resistance to corrosion.
When you add salt water or any electrolyte you eventually get galvanic corrosion between the copper/zinc alloying elements and the aluminium.
If a boom where made of pure alluminium it would bend like butter.

So essentially I have my booms in a bath of electrolyte right now and am hastening, not hindering, their demise.

Probably then its just best to hang them up head first and let them dry after sailing...

I guess the thing is that salt crystals attract moisture from the atmosphere so its likely there's always salty dampness between the alloy and stainless components...

attach a sacrificial anode to it

DrJ said...

I think there is value in at least rinsing your gear with fresh water if it's going to be a week or more before you use it again.

Both sodium and chlorine ions are highly reactive and salt itself is hydroscopic. So if you just let it dry, it will in fact never be dry, as the salt will attract and hold moisture in all the cracks and crannies and corrode continuously, slowly but continuously.

I personally just hose down my gear now and again, certainly before extended periods of storage.

There's sense in what you say. A fresh water rinse to get some of the salt out (hopefully) and then letting them dry out. This might help slow down corrosion.

Eh. Might be time for carbon. I dunno.