OT? GM is spot-welding steel to aluminum!

[Bob Masta]

Detroit newspapers have recently featured a story about GM's
new technique for spot-welding steel directly to aluminum,
eliminating several pounds of rivets per car.

No mention was made of how they avoid corrosion due to
galvanic action. No luck on Google either. Any ideas?

Best regards,


Bob Masta

DAQARTA v9.20
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[George Herold]

On Thursday, May 26, 2016 at 7:57:07 AM UTC-4, Bob Masta wrote:

Detroit newspapers have recently featured a story about GM's
new technique for spot-welding steel directly to aluminum,
eliminating several pounds of rivets per car.

No mention was made of how they avoid corrosion due to
galvanic action. No luck on Google either. Any ideas?

Won't there still be galvanic action with rivets?

(Email the newspaper/reporter maybe they can provide the source?)

George H.

Best regards,


Bob Masta

DAQARTA v9.20
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www.daqarta.com
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[Tim Wescott]

On Thu, 26 May 2016 06:38:54 -0700, George Herold wrote:

On Thursday, May 26, 2016 at 7:57:07 AM UTC-4, Bob Masta wrote:
Detroit newspapers have recently featured a story about GM's new
technique for spot-welding steel directly to aluminum, eliminating
several pounds of rivets per car.

No mention was made of how they avoid corrosion due to galvanic action.
No luck on Google either. Any ideas?

Won't there still be galvanic action with rivets?

In theory you could paint the panels before riveting, and use painted
rivets. That should hold until the vehicle is out of warranty.

--
Tim Wescott
Control systems, embedded software and circuit design
I'm looking for work! See my website if you're interested
http://www.wescottdesign.com

 

On Thu, 26 May 2016 11:57:12 GMT, N0Spam@daqarta.com (Bob Masta)
wrote:

Detroit newspapers have recently featured a story about GM's
new technique for spot-welding steel directly to aluminum,
eliminating several pounds of rivets per car.

No mention was made of how they avoid corrosion due to
galvanic action. No luck on Google either. Any ideas?

Best regards,


Bob Masta

DAQARTA v9.20
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE 8-channel Signal Generator, DaqMusiq generator
Science with your sound card!

Greetings Bob,
Aluminum and steel are commonly explosively bonded for use in the
marine industry. One of the terms for this material is "Transition
Bar". It is used, for example, when an aluminum superstructure is
attached to the steel deck. Besides being a faster attaching method
because the bar is welded to each structure instead of bolting or
riveting, this method of attaching has several other advantages, one
important one being the elimination of corrosion at the aluminum/steel
interface because there is no chance of an electrolyte in the joint,
as there would be in a bolted or riveted joint. Of course if the joint
was underwater the aluminum would corrode much faster than the steel.
I would think the spot welded joint in the cars would act the same.
Eric

 

[Bob Masta]

On Thu, 26 May 2016 09:12:31 -0700, etpm@whidbey.com wrote:

On Thu, 26 May 2016 11:57:12 GMT, N0Spam@daqarta.com (Bob Masta)
wrote:

Detroit newspapers have recently featured a story about GM's
new technique for spot-welding steel directly to aluminum,
eliminating several pounds of rivets per car.

No mention was made of how they avoid corrosion due to
galvanic action. No luck on Google either. Any ideas?

Best regards,


Bob Masta

DAQARTA v9.20
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE 8-channel Signal Generator, DaqMusiq generator
Science with your sound card!
Greetings Bob,
Aluminum and steel are commonly explosively bonded for use in the
marine industry. One of the terms for this material is "Transition
Bar". It is used, for example, when an aluminum superstructure is
attached to the steel deck. Besides being a faster attaching method
because the bar is welded to each structure instead of bolting or
riveting, this method of attaching has several other advantages, one
important one being the elimination of corrosion at the aluminum/steel
interface because there is no chance of an electrolyte in the joint,
as there would be in a bolted or riveted joint. Of course if the joint
was underwater the aluminum would corrode much faster than the steel.
I would think the spot welded joint in the cars would act the same.
Eric

Thanks, Eric. I hadn't considered the fact that with a weld
there could be no electrolyte in the joint. If GM is using
this for joining panels that aren't exposed directly to road
salt, etc, then there wouldn't even be any droplets to
bridge across the weld edges. I suppose for underbody use
the panels would be coated after welding anyway, so even
better protection from electrolytes.

Best regards,


Bob Masta

DAQARTA v9.20
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE 8-channel Signal Generator, DaqMusiq generator
Science with your sound card!

 

On Fri, 27 May 2016 12:14:35 GMT, N0Spam@daqarta.com (Bob Masta)
wrote:

On Thu, 26 May 2016 09:12:31 -0700, etpm@whidbey.com wrote:

On Thu, 26 May 2016 11:57:12 GMT, N0Spam@daqarta.com (Bob Masta)
wrote:

Detroit newspapers have recently featured a story about GM's
new technique for spot-welding steel directly to aluminum,
eliminating several pounds of rivets per car.

No mention was made of how they avoid corrosion due to
galvanic action. No luck on Google either. Any ideas?

Best regards,


Bob Masta

DAQARTA v9.20
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE 8-channel Signal Generator, DaqMusiq generator
Science with your sound card!
Greetings Bob,
Aluminum and steel are commonly explosively bonded for use in the
marine industry. One of the terms for this material is "Transition
Bar". It is used, for example, when an aluminum superstructure is
attached to the steel deck. Besides being a faster attaching method
because the bar is welded to each structure instead of bolting or
riveting, this method of attaching has several other advantages, one
important one being the elimination of corrosion at the aluminum/steel
interface because there is no chance of an electrolyte in the joint,
as there would be in a bolted or riveted joint. Of course if the joint
was underwater the aluminum would corrode much faster than the steel.
I would think the spot welded joint in the cars would act the same.
Eric

Thanks, Eric. I hadn't considered the fact that with a weld
there could be no electrolyte in the joint. If GM is using
this for joining panels that aren't exposed directly to road
salt, etc, then there wouldn't even be any droplets to
bridge across the weld edges. I suppose for underbody use
the panels would be coated after welding anyway, so even
better protection from electrolytes.

Best regards,


Bob Masta

DAQARTA v9.20
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE 8-channel Signal Generator, DaqMusiq generator
Science with your sound card!

Greetings Bob,
You're welcome. Some years ago I got curious about the stuff when my
neighbor gave me a chunk of transition bar. When the metals are joined
they ripple at the interface and these ripples cause the two metals to
physically interlock which provides a really strong mechanical joint.
The size and wavelength of the ripples can be controlled by the amount
and type of explosive used. The explosion is started at one end or
corner of the sheets or plates being joined and the rippling of the
surface drives surface contaminants ahead of the waves, resulting in a
very clean joint. Sometimes two metals can't be joined reliably so a
third metal is sandwiched between the two. I have a chunk of
aluminum, niobium, titanium that was explosivly bonded. The transition
bar I have shows clearly how the waves of metal interlock, with one
wave curling around the other. The spot welded metals you posted about
intrigue me because the joining process is different. Now I need to
look it up to see how it works.
Cheers,
Eric