Carbon Composites bolted to Aluminum (The Head)
12-18-2003, 11:05 AM
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Carbon Composites bolted to Aluminum (The Head)
I was looking for an intake for my car and found this heat sheild installation:
http://www.s2000.org/mods/heatshield/
I kind of bothered me.
I a mechanical engineer for Aloha Airlines, and in college I studied the galvanic corrosoin of Carbon fiber composites coupled with Aluminum. Carbon Composites and Aluminum are far apart in the galvanic chart, so when coupled the Aluminum will corrode exteremly fast. When Carbon Composites are used with Aluminum , the Aluminum is primed, and Painted. The Carbon Fiber is Painted, a fiberglass barrier is installed, Moisture barriers installed, and if bolts are used they are either stainless steel or Ti. See the link below, or do a google search to verify.
http://www.corrosion-doctors.org/Design/ai...raft-design.htm
So, as a WARNING I would recommend staying away from bolting carbon fiber on the engine head, the hood, etc.
Especially, the carbon fiber valve cover. If you seen part installed like the valve cover, and there was no protection like i mention, and no corrosion, it is probally NOT carbon fiber, but more likely fiberglass... FG is okay, because it is only a cover (none structural), will not induce corrsion, and looks good.
http://www.s2000.org/mods/heatshield/
I kind of bothered me.
I a mechanical engineer for Aloha Airlines, and in college I studied the galvanic corrosoin of Carbon fiber composites coupled with Aluminum. Carbon Composites and Aluminum are far apart in the galvanic chart, so when coupled the Aluminum will corrode exteremly fast. When Carbon Composites are used with Aluminum , the Aluminum is primed, and Painted. The Carbon Fiber is Painted, a fiberglass barrier is installed, Moisture barriers installed, and if bolts are used they are either stainless steel or Ti. See the link below, or do a google search to verify.
http://www.corrosion-doctors.org/Design/ai...raft-design.htm
So, as a WARNING I would recommend staying away from bolting carbon fiber on the engine head, the hood, etc.
Especially, the carbon fiber valve cover. If you seen part installed like the valve cover, and there was no protection like i mention, and no corrosion, it is probally NOT carbon fiber, but more likely fiberglass... FG is okay, because it is only a cover (none structural), will not induce corrsion, and looks good.
12-18-2003, 11:44 AM
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Interesting info on the CF corrosion.
FWIW the top link you provided is for a heatshield that is fairly similar to the one offered by Nzaizar/Ricks. The mounting bracket is made of aluminum and bolts up to the aluminum head. The only CF to Aluminum contact is between the shield and the mounting bracket.
Not seeing a CF valve cover??
FWIW the top link you provided is for a heatshield that is fairly similar to the one offered by Nzaizar/Ricks. The mounting bracket is made of aluminum and bolts up to the aluminum head. The only CF to Aluminum contact is between the shield and the mounting bracket.
Not seeing a CF valve cover??
12-18-2003, 12:34 PM
#3
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Galvanic coupling of materials
The objective is to avoid coupling materials from different groups unless required by economic and weight considerations. If dissimilar metal coupling is required, proper finishing and sealing techniques and guidelines are used to prevent corrosion. For example, graphite fibers, which are used to reinforce some plastic structure, present a particularly challenging galvanic corrosion combination. The fibers are good electrical conductors and they produce a large galvanic potential with the aluminum alloys used in airplane structure. The only practical, effective method of preventing corrosion is to keep moisture from simultaneously contacting aluminum structure and carbon fibers by finishing, sealing, using durable isolating materials such as fiberglass, and providing drainage.
The objective is to avoid coupling materials from different groups unless required by economic and weight considerations. If dissimilar metal coupling is required, proper finishing and sealing techniques and guidelines are used to prevent corrosion. For example, graphite fibers, which are used to reinforce some plastic structure, present a particularly challenging galvanic corrosion combination. The fibers are good electrical conductors and they produce a large galvanic potential with the aluminum alloys used in airplane structure. The only practical, effective method of preventing corrosion is to keep moisture from simultaneously contacting aluminum structure and carbon fibers by finishing, sealing, using durable isolating materials such as fiberglass, and providing drainage.
