Degassing Aluminium

Can anybody help me with info on degasing aluminium for automotive bonding.
We are gluing a car chassis and prior to this it is degassed, need to
understand process.
Regards
Fraser
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Fraser Reid wrote:

You typically degas the adhesive, not the aluminum. Yes, it eliminates much of the moisture in the adhesive. You can degas each part of a multi-part adhesive before mixing, and if the working life is sufficient, you can degas the mixed adhesive to prevent air bubbles in the finished product. You can even degas the assembly with the adhesive in place in some cases.
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Dave
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We are degassing the parts.
It is a special process used in bonding chassis in Aluminium for automotive
Any info welcome
regards
Fraser

bonding.
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Fraser Reid wrote:

Do you have references for the procedure? I'm not sure what you are seeking.
You might check the recent thread on this ng about using anodized aluminum in vacuum chamber applications.
If I want to be sure that there is no water on the surface of an aluminum part in preparation for a bonding procedure, I typically specify cleaning with solvents including alcohol and drying in an oven at 60 C for an hour. Double whammy: you get the part clean and dry.
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Automotive aluminium chassis build using Dow chemicals XD4600 adhesive.
You basically glue the structure together and cure the glue in an oven.
Prior to this you "degas" the aluminium in an oven at 200degrees for say 15mins. This removes any moistue from the material so when you glue it you have a strong bond. The bond is as strong as the parent metal, similar to welding.
I will search the web for references and keep you posted.
The Lotus Esprit sports car has a rivited and bonded chassis, the Jaguar XJ has a riveted and bonded chassis as it is also aluminium. This new vehicle is completely structurally bonded.
Regards
Fraser

automotive
seeking.
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Fraser Reid wrote:

Sounds like it would work. You should get rid of the moisture this way. I don't know what your question is, since it sounds like you "understand the process."
How do you clean the aluminum?
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No not really.
How long and how high do you need to "degas" for ? 200degrees for 1hr on 3mm plate ? 180degrees for 1/2 an hour ? Cooling time ? Time allowable back in normal atmosphere before having to repeat process ?
Some questions I don't have the answers to which are important for production.
Regards
Fraser

you
to
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Fraser Reid wrote:

Try the calculations described on this page: http://tinyurl.com/yqcvq (the long URL: http://van.hep.uiuc.edu/van/qa/section/States_of_Matter_and_ Energy/Boiling_Evaporating_and_Condensing/20020321122324.htm)
You'll have to come up with an estimate of the amount of water that you need to eliminate, then you can calculate the proper time/pressure. Multiply the dwell time by a safety factor. You might even find that at your "normal atmosphere," you don't need any extra processes to get rid of water.
> Cooling time ?
Parts are often bonded after being preheated. You may not need any cooling time.
> Time allowable back in normal atmosphere before having to repeat process ?
I don't know. Depending on the environment that you consider normal, perhaps no water will condense on the aluminum.
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How long will be quite different for hot, humid summer days and cold, dry winter days ...
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