Aluminum Adhesive/Sealant with Electric conductive properties

[Vertigo01]

Hello all was wondering if what I am looking for even exists or is phyisically possible... I am looking to bond two thin aluminum parts together in doing so, also create a seal (water/sand-proof). Now usually these parts would then be riveted together but we are looking to drop the rivets and spot weld the aluminum together but still want the sealant to be inbetween the parts and have enough hold that moving between assembly stations the parts will hold. Again not sure if this is even possible but any and all suggestions would be awesome.

Thanks
Tom

 

[CoryPad]

There are conductive sealants, for example:

http://www.masterbond.com/properties/electrically-conductive-adhesive-systems

But the conductive agents used (graphite, nickel, silver) may lead to galvanic corrosion on the aluminium.

Here is a sealant that has a corrosion inhibitor added to counteract the nickel-aluminium reaction:

http://www.ppg.com/coatings/aerospace/sealants1/pr_2201_class_b.pdf

You should contact a few suppliers, try Henkel/Loctite and 3M in addition to those above.

 

[Vertigo01]

Yes the only reason that I need the adhesive or epoxy to be conductive is welding only (spot/resistance weld). The down fall is as CoryPad stated is having dis-similar metals can cause them to begin to corrode which I need to avoid.

The ppg link seems to have some of the characteristics that I would require but I would need to do weld development on some samples before I can show this to our customer. I would like to find something that has been proven to work to avoid the costs of getting testing done but it appears that I am in a unique situtation that has not really been proven out and will require it to begin with.

Thanks again for the suggestions any and all help has been great.
Tom

 

[MintJulep]

Seems the link I posted earlier didn't work. Trying again:

Link

 

[berkshire]

Vertigo01 (Military),
3M makes some aluminum powder filled resins and sealants, you could talk to them.
One danger of spot welding through a sealant on aluminum, is that, not all, of the sealant will move away as current is applied.
Some times overheating your weld spot. You may mitigate this some what, by close control, of your ramp up currents.
B.E.

You are judged not by what you know, but by what you can do.

 

[ScottyUK]

Depending on your part geometry, could you apply an adhesive / sealant using, for example, a screen printer to leave a clean circular area immediately around the location of the spot weld? The sealant would still seal, unless the weld was porous, but the weld would have a far greater chance of being successful.

I doubt that you could weld through sealant: even a conductive adhesive has conductivity far below that of a metal, and I doubt you could pass sufficient current to initiate welding unless you applied such a large electrode force that it caused plastic displacement of the cured sealant prior to welding.

 

[berkshire]

scotty,
I doubt you could pass sufficient current to initiate welding unless you applied such a large electrode force that it caused plastic displacement of the cured sealant prior to welding.
That is the current system , very heavy pressure and long squeeze time, before initiating the current flow, which is short duration.
B.E.

You are judged not by what you know, but by what you can do.

 

[MikeHalloran]

I'd take a look at sealant plus BTM Tog-L-Loc or similar rivetless processes.



Mike Halloran
Pembroke Pines, FL, USA

 

[ScottyUK]

Hi berkshire,

That was the point - conductive adhesives won't be sufficiently conductive to avoid the long squeeze time to displace the adhesive. Even the silver-loaded epoxies, which by adhesive standards are fairly conductive, have a resistivity orders of magnitude greater than that of the metal substrate.

 

[Compositepro]

My initial reaction was very skeptical about spot welding through a sealant, but Mint's link was to a product data sheet that states it can be used as a weld through sealant using conventional spot welding equipment. The description also states it is a water dispersion, and that is spreads like whipped butter.
Obviously the spot welding must be done before the sealant cures. It appears that the sealant has air whipped into it and this allows the sealant to be squeezed out of the weld area so normal spot welding can occur. The sealant is not conductive.

 

[ScottyUK]

Doesn't meet the waterproof requirement though - "... it will lose most of its adhesion if totally submerged in water for 24 hours.". Maybe 'water resistant' is adequate in this application?