Stainless and aluminum

[peb]

Well, its not a wooden boat question, but I'll ask anyway. I have a friend who is restoring an old Catalina 30 (don't bother to ask why, you don't want to know). Anyway, he is putting back together the mast and rig. He says that there are several hardware pieces that are attached to it with stainless bolts going into threaded holes in the mast. Doesn't this cause problems between the two metals? I have had aluminum "weld" itself to a stainless bolt before. Should he treat the bolts with something before he puts it in? He says a couple of years ago, thats what a professional rigger did, but he doesn't know with what.

[Bill Lowe]

Loctite insulates pretty well and keeps the fastner from loosening

[paladin]

Monel bolts might be cheaper in the long run.....

[kc8pql]

Use Tef-Gel. It's made to prevent galvanic corrosion between alu. and SS. You can order from Jamestown Dist. You're right. SS in direct contact with alu will corrode the alu. He should also insulate between any stainless fittings and the mast. Pieces of plastic milk jug work ok.

[peb]

Thanks for the reply everyone. I read up on Tef-Gel and it says that it does not electrically insulate the hardware. If not, how does it prevent galvanic corrosion?

[donald branscom]

Well, its not a wooden boat question, but I'll ask anyway. I have a friend who is restoring an old Catalina 30 (don't bother to ask why, you don't want to know). Anyway, he is putting back together the mast and rig. He says that there are several hardware pieces that are attached to it with stainless bolts going into threaded holes in the mast. Doesn't this cause problems between the two metals? I have had aluminum "weld" itself to a stainless bolt before. Should he treat the bolts with something before he puts it in? He says a couple of years ago, thats what a professional rigger did, but he doesn't know with what.

There are corrosion concerns, but more importantly is the threaded
bolt or screw pulling out of the mast.
It actually happened to me when sailing when a spreader pulled out of the mast. I was under the Golden Gate bridge.
I will skip the whole story but I repaired it by using large 3/16 diameter pop rivets. You need a special rivet gun and you can rent it,or buy it.
The spreader never came off of the mast again.
Think about it a stainless bolt in aluminum. Not much holding power.

[Peter Malcolm Jardine]

A catalina 30 is a good old boat... well built, and a decent sailor if I remember right.

[Chan]

Doesn't locktite make something unremovable?

[paladin]

actually...the bolts should not be threaded to the mast, even with doublers....there should be a compression tube and the bolts run through the tube and secured with nuts and a safety wire....all stainless rigging hardware should be isolated from the mast with teflon spacers or sheet (tangs, etc).....

[Jay Greer]

Spar Craft once recomended the use of a tube goo called "Alumalast" for insulating stainless and aluminum connections. I used it. It worked!
JG

[Figmental]

Permatex "Anti seize", is what I use in any threaded hole in aluminum. Especially in spark plug threads in an aluminum head prone to getting stuck. It is a micro powdered aluminum in a kind of grease that acts as a thread lube, sealant, and air excluder. Stops galling and seizing. Best stuff!

[Norman Bernstein]

I've owned 3 different Catalinas from 1985-2000 (a 30', a 34', and a 40', all bought brand new), and I think they're a competently built boat... not ultra fancy, but highly serviceable... sort of the Chevrolet of sailboats.

Anyhow, Catalinas have always used stainless fasteners in the aluminum mast... whether the factory applies any anti-galling compound or not, I couldn't say. My own personal experience is that it's better not to use any, presuming the fastener is intended to be permanent; the resulting galvanic corrosion is effectvely a better thread-locker than anything you can apply from a bottle.

It becomes more problematic in terms of cosmetic appearances, where large stainless areas meet the mast. The corrosion visible creeping out from under the edge is unsightly, and if the mast has been Awlgripped, the corrosion bubbles the paint. If installing anything like a cheekblock, which has wide surfaces touching the spar, I've found it useful to apply electrical tape as an insulator between the fitting and the spar. The fasteners will still gall, but it won't creep out from under the edges quite so badly.

[peb]

Thanks for the replies everyone. These fasteners are not the spreader bases. Those are through bolted throught the mast. I am not for sure what hardware it is, I assume something rather light load, as he said they are #8 size bolts.