carbon fibre

vti2003 · Post by **vti2003** » Sat Mar 31, 2012 9:28 pm

Be careful skinning metals directly with carbon. If the carbon contacts the steel it causes pretty severe galvanic corrosion. Either prime the metal with a sealed epoxy primer and then skin or best or all use a blocker layer of fibreglass between the metal and carbon

Carbon corroding metals has been a massive problem in aerospace for years.

littlefeller · Post by **littlefeller** » Sat Mar 31, 2012 9:33 pm

that makes it harder, cant skin under the skin cause the doors wont shut and the rubber allaround wont be any good

would have to be a chemical barrier, although easy is just another expense

do you happen to know why? is it the carbon as i have never come across this with fibre glass

vti2003 · Post by **vti2003** » Sat Mar 31, 2012 9:45 pm

It is the carbon, fibreglass doesn't do it.

I may not be 100% right as I am digging in the depths of my memory here

I think it is because for this type of corrosion to occur you need an anode and a cathode, Fibreglass is, as the name suggests, made from glass which is an insulator and as such cannot act as a cathode. Carbon however is a very good conductor and can therefore act as a cathode, the metal itself will act as the anode.

So carbon and metal = anode and cathode - corrosion, whereas glassfibre and metal = anode only = no corrosion.

The same process as dissimilar metal corrosion where two different type of metal in contact with each other will corrode.

I think.......................

As said before just use a layer of fibreglass between the metal and carbon. That's what boeing and airbus do.....

Post by **paul bristol uk** » Sat Mar 31, 2012 9:51 pm

vti2003 wrote:
The same process as dissimilar metal corrosion where two different type of metal in contact with each other will corrode.

I think.......................

That bit is true from my days or restoring classic big Healy's with ally scuttles and steel wings. As for the rest of your post I will take your word for it!

vti2003 · Post by **vti2003** » Sat Mar 31, 2012 10:10 pm

If you look at the chart below it explains. The bigger the gap between the materials the more likely corrosion is. Mild steel is quite far on the right as is aluminium while graphite (Carbon) is on the far left. Big gap = big rust

The new Boeing 787 has had to use loads of titanium for fittings instead of aluminium as the main fuselage is made entirely from carbon fibre. The chart shows why. Titanium is very close to graphite and will not corrode like ali, as well as expanding at a similar rate to carbon when heated.

So when you are delaing with carbon treat it as a metal for corrosion purposes.

littlefeller · Post by **littlefeller** » Sun Apr 01, 2012 7:21 am

i remember this now, yes you are correct. the skin will be sitting onto a layer of primer, still havnt made up my mind to either attach it (bonded together) or have it detachable, the problem there would be moisture,

mercutio · Post by **mercutio** » Sun Apr 01, 2012 7:56 am

yeah to prevent the moisture getting in it would have to be bonded could you use an epoxy primer

littlefeller · Post by **littlefeller** » Sun Apr 01, 2012 8:40 am

bonding would be easy, just key the primer, the skin has a resin undercoat, but i was thinking i could make them detachable then i could make more, just use silicone to stick them down, they would be held in place by the rubber seal, but bonding would prob be best.

littlefeller · Post by **littlefeller** » Sun Apr 01, 2012 9:16 am

heres some i stole off google

By littlefeller2010 at 2012-04-01