carbon fiber causing steel corrosion

[wash u fsae]

I've researched bonding carbon fiber to steel and I seem to have found quite a few studies linking corrosion to direct carbon fiber contact with steel. Has anyone had any experience with this? Have any teams bonded carbon fiber to steel?

[vinHonda]

Upon close inspection of our 2002 and 2003 cars..... no corrosion. Although, the carbon only is a small line touching the steel, most of what is bonded/touching the steel is the nomex core.

Vinh

[-]

If you do some more reaserch you will find that eliminating the corrosion problems between composites and metals is a large problem. It is something that the aerospace and the military have spent a large amount of time and $$$ on. Also what enviorment did the research say the parts were in. From what I remember the enviorment played a large role also.

just food for thought.

[leclercjs]

On this, I've done a research because we may be thinking doing an half and half steel/carbon fiber frame and many people told me that anodizing your frame would help slow down the effect of corrosion.

Just a hint, not the answer to the problem.

But Vihn, on you pictures of this year's car, is the frame anodize or it is the frame painted in green?

[Didier Beaudoin]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by leclercjs:
On this, I've done a research because we may be thinking doing an half and half steel/carbon fiber frame and many people told me that anodizing your frame would help slow down the effect of corrosion.

Just a hint, not the answer to the problem.

But Vihn, on you pictures of this year's car, is the frame anodize or it is the frame painted in green? <HR></BLOCKQUOTE>

How can you anodize steel? http://fsae.com/groupee_common/emoticons/icon_confused.gif AFAIK, anodizing is for aluminium only...

On my point of view a primer plus a good coat of paint does the trick, as much as a cadmium plating like we see on bolts and nuts.

[Brent Howard]

Dider,

I was going to post the same thing about anodizing, but normally when I say something like that someone proves me wrong http://fsae.com/groupee_common/emoticons/icon_wink.gif. However, anodizing is only for aluminum.

I was wondering about the painting comment though. Although I think this corrosion must be simaler to galvanic corrosion and so any seperation of the steel and carbon, or carbon resin (??) would be good I'm not so sure paint would be a good idea. The reason I say this is that now you are bonding to the paint and relying on that steel paint and paint-carbon resin bond to hold your parts together. Also, remember that you need water (or another electrolyte) to have any corrosion, so just keep the car dry normally and don't let it sit out in the rain and it will be fine.

Brent

[dancin stu]

At work last year, we were bonding carbon floorpans to steel chassis. The chassis were shot blasted and epoxy powder coated before bonding. We abraided the powder coat with a very course grit, being careful not to go through to the steel, before using two part epoxy resin to glue them together. The bond was incredibly strong, one chassis survived some extreme abuse courtesy of torsional testing, and nos igns of corrosion were evident. Im guessing if comprehensive lab work were carried out, the powder coat would fail before the glue, although the powder coat is very very durable, and almost impossible to remove, certainly not with a file.

Don't know how feasible powder caoting would be for a Formula Student car, I believe it is quite expensive, but the finish is excellent.

[Brent Howard]

Powdercoat definitly bonds stronger than regular paint. It is fairly cheap too for an FSAE chassis. We had our 2002 chassis powdercoated and it cost around $350 I think. The weight added however was rather high, 5lbs over the same chassis painted.

Brent

[dancin stu]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>The weight added however was rather high, 5lbs over the same chassis painted.

Brent <HR></BLOCKQUOTE>

Thats the thing, think the judges might pick upon it, these chassis are not used every day, and owners will probably keep them away from moisture, although you can forget about chassis maintenance if it is done

[Didier Beaudoin]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Brent Howard:
Dider,

I was going to post the same thing about anodizing, but normally when I say something like that someone proves me wrong http://fsae.com/groupee_common/emoticons/icon_wink.gif. However, anodizing is only for aluminum.

I was wondering about the painting comment though. Although I think this corrosion must be simaler to galvanic corrosion and so any seperation of the steel and carbon, or carbon resin (??) would be good I'm not so sure paint would be a good idea. The reason I say this is that now you are bonding to the paint and relying on that steel paint and paint-carbon resin bond to hold your parts together. Also, remember that you need water (or another electrolyte) to have any corrosion, so just keep the car dry normally and don't let it sit out in the rain and it will be fine.

Brent <HR></BLOCKQUOTE>

Brent,

I'm not sure about galvanic corrosion needing an electrolyte to happen. After all, the materials are exchanging electrons directly from one to another since they are in contact...

[Brent Howard]

Every corrosion cell needs and eletrolyte to corrode. Things will not corrode in dry conditions.

Brent

[Ryan Schoffer]

often the moisture in the air is enough to corrode even bare steel - i have seen it when restoring the supra if i dont paint a piece right after removing the rust and using all the nasty chemicals - it will surface rust within a week

that is why steel stock is coated in a thin layer of oil from the foundry

i would think a stronger cell like the steel/carbon fibre one would be even more prone to corrosion

[Brent Howard]

Basic corrosion theory says that you need 4 elements to make an electrochemical corrosion cell. These elements are, the anode (metal corroding), The cathode (metal or other conductor which provides an enviroment to react), the electrolyte (aqueous enviroment that provides a path for ionic conduction), and an electrical conduction between anode and cathode. If any one of these is not present corrosion cannot occur. The mositure in the air cannot be in gaseous form and couse corrosion. Condensation, even small amounts must be present. Just take a quick look at all the scrap steel that we have sitting machined outside the machine shop...still shiny isn't it. The little bit of corrosion on hot rolled steel is caused by conditions at the time of hot rolling. Notice that cold rolled steel is not corroded on it's exterior before machining.

Brent

[leclercjs]

Oups, my mistake on anodization!!! I mixed up some data a guy gave me from is report where he said anodizing an alu frame with carbon fiber could be a good choice.

And as brent said, you need the four elements to create an electrochemical cell. That would mean putting you fsae frame in a tank full of seawater and without the epoxy between the carbon and the bare steel.


I would like to see that!!

[Brent Howard]

[QUOTE]Originally posted by leclercjs:
And as brent said, you need the four elements to create an electrochemical cell. That would mean putting you fsae frame in a tank full of seawater and without the epoxy between the carbon and the bare steel.
QUOTE]

Not necessarily Jean, The resin may conduct (i'm not sure, which would supply an electrical connection, and then all you need is a small droplet of water on the surface.

Brent

[Ryan Schoffer]

doesnt need to conduct - that is the 'beauty' of steel - it can act as both the anode and cathode at the same time, and corrode with something as simple as condensation from the air

from what i have looked into so far, the corrosion problems have something to do with the carbom fibre holding moisture against the surface, and accelerating the corrosion reaction

[Brent Howard]

Ryan,

Steel acting as both anode and cathode has nothing to do with carbon fiber accelerating corrosion. That is simply general steel corrosion, nothing special. I doubt that the only reason that the carbon accelerates corrosion is the holding of water on the surface. If so then every team would be whining about how the foam on the roll hoops is holding moisture against the chassis and corroding the roll hoops.

Brent