Bolt material?

[Bern]

I will be penetrating the hull with bolts. She will be used in fresh water, probably never see salt. What is the best type to use, stainless steel? The hull is aluminum. When inserting the bolts, I plan on using a sealant of some type. What would you use? --- Thanks for the help.

[Karsten]

The best is Titanium because the electrochemical potential is the smallest to prevent electrolytic corrosion between the fastener and the aluminium. If you use stainless steel fasteners try to get some that are cadmium plated. Otherwise you have to electrically insulate the bolt from the aluminium. Painting the bolt and the hole with a good epoxy primer before installation should do the trick.

[marshmat]

Stainless steel isn't really stainless, of course... in an anaerobic environment it will still corrode (ie. if moisture is trapped under a sealant). The epoxy primer would be of great help in preventing this. Electrically insulating the bolt from the hull is a Very Good Idea as any metal contact will set up a galvanic cell and generate corrosion.

[Dutch Peter]

Originally Posted by Bern

I will be penetrating the hull with bolts. She will be used in fresh water, probably never see salt. What is the best type to use, stainless steel? The hull is aluminum. When inserting the bolts, I plan on using a sealant of some type. What would you use? --- Thanks for the help.

Bern,

Since the previous posters didn't ask, I will. Why are you going to penetrate the hull with bolts? Is there no other solution, since corrosion can become a problem with the bolts?

Regards,

[FAST FRED]

The "best" bolts would be made from the same series if alunimum the hull is coinstructed of.

This is Usually difficult to find ,

but for 3/16 or 1/4 diameter inch structural rivets
( installed with rivet gun & bucking bar)
would work fine , and are usually avilable in Marine grades.

FAST FRED

[Bern]

Dutch Peter, Yes, I need to attach some brackets on the stern. I believe that the best approach is to use nuts and bolts and penetrate the hull skin in order to tie into some brackets on the inside. Some will be above water line, however some will be right at WL.

[D'ARTOIS]

You may use monel, that material is used on alu masts in way of blind rivets and their corrosion rate is the lowest. For the rest I believe Fred is correct - you can use indeed Titanium as Karsten says, but you won't find those required not that easy save in the aircraft industry at some dollars a piece. Keep with Fred or use monel.

[PowerTech]

This dude is probly bolting something to the back of his jon boat and yall are talking about titianium.come on.what sort of boat do you got?if it is a little fishing boat for fresh water just get some stainless bolts and some marine silicone and let it rip.Who cares it aint the friging space shuttel.if it is a real boat or yacht weld it on if you can

[yokebutt]

Bern,

You can always get some thin G-10 from the nearest TAP plastics and cut some washers with a hole-saw and put them under the stainless ones.

Yoke.

[Skippy]

That's hilarious, he didn't say what kind of boat, did he? I'll defend the guys answering so far, the original post does sound kind of serious, and corrosion is a very serious problem on a yacht. How many people call their jon boat "she"?