Dissimilar metal protection

[toddo1]

Hey guys, I'm in the middle of my boat project and just thinking in advance bout stainless screws to aluminium! Now I'm going to buy some tef gel or duralec etc but not sure how much I need, and it's not cheap but want to do everything spot on!! I have to screw my floor/ deck/hinges and other fit outs etc to a 420 explorer! So has anyone had experience in how much I will use? Hard question I know but hopefully someone can help!!

thnx guys

[Shark Poker]

Whale Oil..

[toddo1]

Couldn't find anything on quantity tho shark

[cwcarter]

The tooth paste size tube of duralec will go along way.

[scottar]

Duralac is like sikaflex - one drop will mysteriously coat the entire bloody boat. Tefgel is a much nicer product to use with nowhere near as much clean up required.

[GBC]

A tub of industrial lanolin is as good and cheaper. You are never going to prevent galvanic reaction on a screw anyway. To do it correctly you need a bolt with nylon isolation sleeve and nylon washers.

[Greg P]

Totally agree with GBC. Ive had 3 plate boats built over the last 20 years (shit where did that time go !!) and you will never totally stop it although my last Fisher they just about got it 100% right. I think first rule of thumb is use alloy on alloy whenever possible and have it welded or alloy pop riveted rather than bolted but not sure of your mods and whether that is practical. Best thing on the Fisher is where there is a need for bolts they are all nylon bar the outrigger bases and I take them off each year to clean thoroughly then replace rubber mounts and reseal with duralec.

[Fed]

Got me beat why alloy bolts aren't more popular, has anyone tried them?
http://www.probolt-australia.com/
Surely they'd be better than stainless, good range, buy in small quantities and apparently pretty strong.

[AndrewB]

Cant remember where I discovered this gem but use PH grease in lieu of Duralec. It is a white grease will last a lifetime and is not like most greases, less greasy if that makes sense. Used it on several boats and great stuff.

[PB]

This is the best stuff on the market, highly recommend http://tefgel.com.au/

[blairv70]

Another vote for Tefgel - Best I have used so far. It does not seem to dry out like Sika or Duralac.

I would also use SS bolts + Nylocs for fastneings. I have found self taping screws into Ally seem to be more prone to corrosion as well so I bolt where possible.

But as has been said - you will never stop it entirely

[toddo1]

Everything is welded except for pot rivets which are aluminium too!! Only ss screws I will use is to screw deck down!! I will throw up a few pictures

[juggernaut]

I've got a 13 year old quinnie and the s/s deck screws don't seem to cause a problem and guess the deck itself keeps the water off the fixing point - therefore no corrosion.

Also agree with what other have said including:

Ali rivets where possible;
Bolts in preference to screws;
Nylon washers;
Screw caps;
Sika, Tefgel, Duralec, even grease on the threads helps.

[TheRealAndy]

Got me beat why alloy bolts aren't more popular, has anyone tried them?
http://www.probolt-australia.com/
Surely they'd be better than stainless, good range, buy in small quantities and apparently pretty strong.

Different type of aluminium, you still get galvanic corrosion.


You are never going to prevent galvanic reaction on a screw anyway. To do it correctly you need a bolt with nylon isolation sleeve and nylon washers.

This.

But for what its worth, duralac is what they use on aircraft, so it must have something going for it. I have used tefgel on the boat, and whilst its not as messy, I dont reckon its anywhere near as good as duralac.

[bigjimg]

Have you thought about using a nylon insert?? Screw your floor down as you would, then take out all screws and floor and redrill for the nylon insert, refit your floor and re-screw into the insert. All types of sizes available from any good automotive outlet. Job done. Jim.

[scottar]

The best way I have found is to stop the water getting in. Even with a plastic fitting, if the water gets between it and the ally and sits - corrosion will occur. Now with my tinnie, everything is bedded into plenty of silicone (neutral cure) to prevent any moisture getting in to start with. Any metal fittings are isolated apart from where the bolts pass through the hull using nylon washers or plastic mounting pads - once again bedded into silicone to stop the water. You could use Sika to achieve the same results but if anything requires removal, you are in a world of hurt. Silicone does apparently cause issues if the area of application later requires welding, but it is a heap easier to work with / remove.

[deckie]

Duralac is actually banned in many countries...which leads me to think it must be pretty bloody good :thumbup:
But hey, i'm the type that would happily use agent orange or deildrin coz at least i know it works.

Try not to get the Duralec on the dog either...it will bugger off and then try to lick it off, and next thing you know its $3000 up the vets and a few crying kids. Works though.

Nylon washers and collars when possible.

[Fed]

Different type of aluminium, you still get galvanic corrosion.
Have you ever tried aluminium bolts Andy?


Compatibility with aluminum. It is standard practice to fasten aluminum with aluminum in order to minimize the danger of galvanic corrosion.
http://www.aluminumfastener.com/images/catalog.pdf
Page # 1 Andy. Sounds like a no brainer to me, if I had an alloy boat I'd give them a trial for sure, especially an expensive platey.

Surely aluminium bolts would be at least as good as aluminium rivets?

[TheRealAndy]

Have you ever tried aluminium bolts Andy?


http://www.aluminumfastener.com/images/catalog.pdf
Page # 1 Andy. Sounds like a no brainer to me, if I had an alloy boat I'd give them a trial for sure, especially an expensive platey.

Surely aluminium bolts would be at least as good as aluminium rivets?

I performed a test on them years ago. They are better than stainless fastners, but they still cause corrosion nonetheless.

[toddo1]

Shit defiantly keep the mut away lol