Hello,

I want to assemble à Wing (hydrofoil) onto a 1 inch carbon tube. I wanted to wrapp an aluminium plate with carbon fiber around the tube so to be able to drill and bolt into the aluminium.

I see there can be some galvanic corrosion. What should i do to isolate the aluminium? Would a simple coat of resin be enough ? Is there some minimum thickness ?

These could be out at sea... And although the AL is going to be into the part, the bolts (stainles steel) are going to be into the Al...

Is there the same problem with brass ?

regards

Thanks for the videos and all of the site. It is very "pro".

Franck

There is no minimum thickness and resin wont work.  Coatings or barrier material is often used but the general practice is to put one layer of fiberglass in between the mount points. So a the lay up from the surface would be carbon fiber, fiberglass (in mount points) and then AL.  This creates a barrier between the carbon fiber and the Al and you wont have any corrosion. 

Be aware that the same problem (galvanic corrosion) is very likely between the Aluminium and the stainless steel ... Stainless steel contains large amounts of chrome wich has a high electrical potential to Aluminium.

The expensive solution to this is to use titanium bolts ...

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You could use a stainless fitting.  Using an alloy fitting in the sea isn't going to end well!

As already mentioned, a thin layer of glass is commonly used to insulate the carbon and aluminium for this purpose.

Insulating between two dissimilar metals is another issue.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Certain aluminium alloys are considered "sea-water proof"  or "Sea-water resistant"  They tend to resist the galvanic corrosion from stainless bolts quite well, but not perfectly, so a very "gooey" insulating mounting paste is usually used when mounting the bolts.  

We tend not to think about it but certain conditions can also corrode the Carbon fibre itself ...   and some of the resins we employ in CF composites are in reality slightly porous, and can sometimes absorb water..

If you are using CF composites in a sea-water environment, it always pays to protect it with at least a high quality Marine clear coat.
 
   

"Sapere Aude"... Dare to KNOW!

The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind...

103% of all people do not understand statistics...

Do not adjust our mind, theres a fault in reality :-)

Thanks for all the replies

I have Au4G which isn't great for corrosion so I'll try to use brass or stainless steel inserts.

Franck