Electrolysis with zinc & stainless steel screws on aluminium boat hull
Is there anyone out there who might be able to advise me as to what is the effects of using stainless steel or galvanised screws (zinc coated) onto an aluminium boat hull in regards to electrolysis. Ie, will the stainless steel and gal break down before the aluminium or the other way around. I don't want to end up with holes in the hull like I have been told lead sinkers sinkers can do.
Thanks in anticipation.
Re: Electrolysis with zinc & stainless steel screws on aluminium boat hull
Jack,
There is lots of stuff about this on ausfish. Go search for more.
In summary (my version anyway):
Don't use zinc-cadmium or zinc-galv screws/bolts in alumnium ever. Depending on lots of things, they will amalgamate (and dissolve) with the aluminium in weird ways - all bad.
Use S/S (only 316 if below the waterline) and use duralac (a tube costs up to $30 but lasts forever if you are careful with the lid etc) in the hole, the bolt, washer and nut.
If selftapping screws in, first tap them, then remove, put duralac in the hole, then reinsert the screw.
If no duralac, then use marine sikaflex. If no sikalfex and desperate, use neutral cure roofing silicon - but use something - you will be amazed at how fast the hole and surrounding area corrodes (white powder...) and bubbles...and it gets worse quickly, evenutually leading to pinholes around chines and keels.......
Even if you don't use your boat often, you can still watch the corrosion happen in the comfort of your carport (though a bit slower.....).
Note that it is the aluminium that will break down - though the screws/bolts and fittings may discoulor and gradually break down also.
An alternative often forgotten about is to use marine grade (sealed end) aluminium rivets - these are available at serious bolt shops - though even blunnings now carries some. But even then use duralac or something......particularly below the waterline or on the hull.
Re: Electrolysis with zinc & stainless steel screws on aluminium boat hull
alcam,
Thank you very much, this is very helpful.
Many Regards, Jack
Re: Electrolysis with zinc & stainless steel screws on aluminium boat hull
Jack,
Visit this website:
www.tefgel.com.au
It may solve your problems.
White Pointer
Re: Electrolysis with zinc & stainless steel screws on aluminium boat hull
You can get away with using ordinary aluminium pop rivets.... as long as you drive the remaining steel mandrel out of the rivet with a punch the fill the rivet with sealer such as sicaflex.
bed everything on some sort of sealer...........if using rivets get sealer under the head of the rivet...... silicon is not good... polyeurathane is far better...... sicaflex is king...... bostic gold isnt bad.
As for zinc plated hardware.......even just out in the rain the zinc goes off pretty quick....... if you put an unprotected zinc plated steel screw in an aluminium boat......I would expect to see corrosion in weeks........steel and aluminium not good at all.
cheers
Re: Electrolysis with zinc & stainless steel screws on aluminium boat hull
Quote:
Originally Posted by
oldboot
You can get away with using ordinary aluminium pop rivets.... as long as you drive the remaining steel mandrel out of the rivet with a punch the fill the rivet with sealer such as sicaflex.
Good idea. Sealed rivets have a steel mandrel = VERY BAD!
Re: Electrolysis with zinc & stainless steel screws on aluminium boat hull
You can get aluminium rivets with aluminium shafts....but... if you dont seal the hole in the rivet it will retain water and salt...and will be a source of rapid corrosion.
Just make sure you catch the mandrel when you punch it out.
I sometimes put a slack bit of gaffa tape over the back of the rivet to catch the mandrel.
cheers
Re: Electrolysis with zinc & stainless steel screws on aluminium boat hull
there is a whole host of Marine Pop rivets available that are suitable for Aluminium, and no need to get rid of the centre, they are also waterproof, only thing worse on Alloy than steel/zinc plated is Brass, that is a certain no no!!!
Re: Electrolysis with zinc & stainless steel screws on aluminium boat hull
Quote:
Originally Posted by
Noelm
there is a whole host of Marine Pop rivets available that are suitable for Aluminium, and no need to get rid of the centre, they are also waterproof, only thing worse on Alloy than steel/zinc plated is Brass, that is a certain no no!!!
Where i can I buy sealed aluminium rivets with an aluminium shaft in a packet of 100 or less, the sealed rivets at bunnings have a steel shaft
Ken
Re: Electrolysis with zinc & stainless steel screws on aluminium boat hull
try "The bolt king" at capalaba.
cheers
Re: Electrolysis with zinc & stainless steel screws on aluminium boat hull
Hi,
Zinc is next to aluminium on the galvanic table, therefore there should be very little chance of corrosion if you use galvanised fittings on aluminium
I built an aluminium trailer a little over two years ago, and all the fittings on it are galvanised ie bolts, nuts, axles, discs, springs, multi roller fittings.
After two years of use, there is no sign of corrosion around any of the fittings!
It may happen eventually, but I am keeping an eye on it.
I always use Duralac with stainless bolts or screws.
I have never had a problem with al rivets with al mandrels.
Dave.
Re: Electrolysis with zinc & stainless steel screws on aluminium boat hull
Quote:
Originally Posted by
Steboe
Where i can I buy sealed aluminium rivets with an aluminium shaft in a packet of 100 or less, the sealed rivets at bunnings have a steel shaft
Ken
I get mine from whitworths
cheers fnq
Re: Electrolysis with zinc & stainless steel screws on aluminium boat hull
Bias boating also sell them in a couple of different sizes singly.
Dve.
Re: Electrolysis with zinc & stainless steel screws on aluminium boat hull
OK, first off, forget Bunnings, we are talking Marine here, so off to a yacht ot Boat supplies place you go, and you will be able to buy them as easy as pie!
Re: Electrolysis with zinc & stainless steel screws on aluminium boat hull
http://www.ausfish.com.au/vforum/mem...310-suzygs1000
I know its been a long time since you posted this. Just checking to see if you have had any negative effects from the Galvanised stuff in the Aluminium trailer.
I was looking to put some galvanised braces into the floor in my Aluminium boat as supports above the infloor fuel tank (also aluminium).
I have put rubber bike tube over the galvanised square tubes and no actual contact with the fuel tank, was using Tefgel and rubber washers between the 316 stainless steel bolts that attach the galvanised braces to the aluminium boat upper braces.