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Discussion Starter #1
“We saved just shy of 50lbs by using all aluminum enclosures (all the exterior body panels are aluminum). The underbody is 95% high strength steel or advanced high strength steel, some of it is the first time it’s been used in production so far. The upper body, not counting the exterior panels is about 80% high strength steel, so there is a lot of advanced materials in there, but we didn’t use carbon fiber anywhere I can think of.”

I know the Model S uses aluminum, while my Volt uses High Strength Steel (except for the hood). Having a "door bang" fender dent repaired on the Volt by a paintless dent repair service was flawless and quick.

I understand aluminum is trickier, with it's own set of pro's and cons compared to steel. So I thought it might be good to explore what a Bolt EV buyer can expect in the way of pluses and minuses with aluminum body panels.

Anyone with direct experience?
 

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I would say that the obvious plus is weight, and the obvious con is difficulty/cost of repairs. Outside of that, it gets a little more situational. Aluminum has far better corrosion resistance, but steel might have better NVH resistance. Aluminum, especially in the case of the roof, suffers from lower levels of heat soak, but it also might be a worse insulator during winter.

All in all, as a personal preference, I would choose aluminum over steel for non-structural components.
 

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I would agree NVH is better for steel.

Aluminium is initially good for corrosion, but if it is not bonded to other metals 'correctly' it can corrode very quickly and beyond repair. It can even become a sacrificial galvanic anode, and has a bigger electro-potential than zinc in that respect, so simply connecting it to a steel body can cause the Al to start corroding if porous aluminium hydroxides are formed.
 

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Nissan used aluminum for the body panels on the 2011-2012 Leaf and Ford uses it on the F-150. It has worked out well in both cases. Thus, I have no concern about it...
 

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Aluminium is initially good for corrosion, but if it is not bonded to other metals 'correctly' it can corrode very quickly and beyond repair. It can even become a sacrificial galvanic anode, and has a bigger electro-potential than zinc in that respect, so simply connecting it to a steel body can cause the Al to start corroding if porous aluminium hydroxides are formed.
I was assuming the GM engineers would know better than to do that. :D

Also, don't plan on visiting the Gallium Water Park.
 

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Discussion Starter #7 (Edited)
Nissan used aluminum for the body panels on the 2011-2012 Leaf and Ford uses it on the F-150. It has worked out well in both cases. Thus, I have no concern about it...
I understand that Ford has setup a network of certified body shops for repair of F-150 aluminum body panels. Perhaps GM will be doing the same?

I always thought Saturn's use of resin body panels was a great idea, but the cons vs. steel were slow production rates, more expansion/contraction requiring bigger gaps around doors, hoods and trunks. So they went back to steel. Interestingly, the Volt concept car had a GE thermoplastic hood, though production uses aluminum.

Those who have experienced the "acorn dropping" pop in the Volt's rear when the plastic spoiler expands/contracts, or those who may have a slight misfit of the Volt front bumper where it joins the steel fender are experiencing living examples of plastic expansion/contraction effects.

Another potential downside to aluminum is bubbling paint if the surface has not been prepped correctly. But given all the jet's that are aluminum bodied, I'd expect painting aluminum should not be a mystery. Then again, Ford issued a number of TSB's to correct paint issues on some F-150's. At the same time, I see many, many posts about Tesla paint issues. https://www.google.com/#q=tesla+aluminum+paint+issues Whether these are caused by poor paint, poor prep, or poor technique I can't say. Interestingly, when searching for GM paint issues with aluminum, not much comes up, and what does is mostly links to Ford F150 issues related to bad prep. https://www.google.com/#q=GM+aluminum+paint+issues

So is the Bolt EV GM's test bed for using all aluminum body panels? Almost.

The Cadillac CT6 sedan is GM’s first high-volume vehicle to use all-aluminum outer body panels. My hope is that GM won't risk blemishing the CT6 with paint prep that leads to paint failure and the Bolt will piggyback on that process, just like it's doing with the very cool camera rear-view mirror. But you would have thought Ford would have been equally diligent with it's F-150.
 

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Our 2008 Jaguar was all aluminum and there were only a handful of shops in the St Louis area that could handle any collision repairs. In fact there was an entire section in the Owners Manual devoted to this issue. Jaguar even included FREE towing to the nearest authorized repair facility. FYI my 2008 XK listed for $88K so I guess they could provide that kind of service.
 

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I think an interesting alternative to paint with aluminum panels would be to use anodizing techniques, but I'm not sure whether the costs would outweigh the benefits.
 

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I think an interesting alternative to paint with aluminum panels would be to use anodizing techniques, but I'm not sure whether the costs would outweigh the benefits.
You mean the way Apple makes their gold, silver, black, and pink watches, tablets, phones, and laptops? I wonder if someone might someday take a giant solid chunk of aluminum and mill a car frame and body out of it. There would be a lot of waste that could be remelted into new material, but it would also eliminate a bunch of bolt on structures
 

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I half-expected GM to go with the same material they used for the Corvette. The article link below suggests the composite is both lighter and cheaper than aluminum. But the aluminum may be easier to repair than composite and if the Bolt is used as an urban taxi or Lyft type vehicle playing urban bumper cars, composites might not be the best material. Or maybe the Corvette body is a retail low-volume "experiment" and GM is still evaluating the composite materials game.

C7 Corvette composite body panels
 

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Discussion Starter #12
I think an interesting alternative to paint with aluminum panels would be to use anodizing techniques, but I'm not sure whether the costs would outweigh the benefits.
Too much bling for some? A better Bricklin or Delorean for others? I imagine it would not make repairing a damaged panel less expensive. But maybe you just proudly wear your anodized dents like a distressed wooden door or table. :)

annodized aluminum.jpg annodized aluminum cups.jpg annodized aluminum wheels.jpg
 

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It wasn't the video I wanted people to take note of...it was the article...:)

GM Welding Breakthrough Enables More Use of Aluminum

Increased use of lightweight metal can help improve fuel economy, performance

2012-09-24

DETROIT – General Motors Research & Development has invented an industry-first aluminum welding technology expected to enable more use of the lightweight metal on future vehicles, which can help improve fuel economy and driving performance.

GM’s new resistance spot welding process uses a patented multi-ring domed electrode that does what smooth electrodes are unreliable at doing – welding aluminum to aluminum. By using this process GM expects to eliminate nearly two pounds of rivets from aluminum body parts such as hoods, liftgates and doors.

GM
already uses this patented process on the hood of the Cadillac CTS-V and the liftgate of the hybrid versions of Chevrolet Tahoe and GMC Yukon. GM plans to use this technology more extensively starting in 2013.

“The ability to weld aluminum body structures and closures in such a robust fashion will give GM a unique manufacturing advantage,” said Jon Lauckner, GM chief technology officer and vice president of Global R&D.

“This new technology solves the long-standing problem of spot welding aluminum, which is how all manufacturers have welded steel parts together for decades,” Lauckner said. “It is an important step forward that will grow in importance as we increase the use of aluminum in our cars, trucks and crossovers over the next several years.”

Spot welding uses two opposing electrode pincers to compress and fuse pieces of metal together, using an electrical current to create intense heat to form a weld. The process is inexpensive, fast and reliable, but until now, not robust for use on aluminum in today’s manufacturing environment. GM’s new welding technique works on sheet, extruded and cast aluminum because GM’s proprietary multi-ring domed electrode head disrupts the oxide on aluminum’s surface to enable a stronger weld.

Historically, automakers have used self-piercing rivets to join aluminum body parts, because of variability in production with conventional resistance spot welding. However, rivets add cost and riveting guns have a limited range of joint configurations. In addition, end-of-life recycling of aluminum parts containing rivets is more complex.

No other automaker is spot-welding aluminum body structures to the extent we are planning to, and this technology will allow us to do so at low cost,” said Blair Carlson, GM manufacturing systems research lab group manager. “We also intend to consider licensing the technology for non-GM production in automotive, heavy truck, rail and aerospace applications.”

According to Ducker Worldwide, a Michigan-based market research firm, aluminum use in vehicles is expected to double by 2025. The material offers many advantages over steel. One kilogram of aluminum can replace two kilograms of steel. It is corrosion-resistant and offers an excellent blend of strength and low mass that can help improve fuel economy and performance.

According to AluminumTransportation.org, a 5 percent to 7 percent fuel savings can be realized for every 10 percent weight reduction, and substituting lightweight aluminum for a heavier material is one way to do it. Cars made lighter with aluminum also can accelerate faster and brake quicker than their heavier counterparts.

“GM aims to be an industry leader in mass efficiency,” said Roger Clark, manager of the GM Energy Center. “Many little things can add up to big improvements in fuel economy. Incremental mass reductions, like using welds instead of rivets, can help our customers save at the pump.”
 

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It can even become a sacrificial galvanic anode, and has a bigger electro-potential than zinc in that respect, so simply connecting it to a steel body can cause the Al to start corroding if porous aluminium hydroxides are formed.
And that's exactly the one I was thinking "hmmm... This could end up Interesting," when I read about the extensive aluminum use.
 

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Some things not already stated:
Aluminum is not as strong and therefore requires thicker parts with larger bend radii. Panels will not look as sharp edged.
Aluminum melts at a much lower temperature than steel and won't provide as much fire protection,
Aluminum still requires many more fasteners and holes to be produced for those fasteners. Riveting is very sensitive to cracking at the fastener. All of these make for a more time consuming and more expensive construction.
Aluminum raw materials are produced by far fewer companies which can lead to higher prices and shortages especially of proprietary alloys. Ford bought several aluminum producers to stabilize their supply and costs.
Aluminum scrap must be kept separate from steel during manufacture and end of life recycling.
 

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I actually 100% agree with HVACman and think that was the point of OP...Should GM with it's experience with Saturn's and Corvettes body panels, should they even invest into heavier aluminum? Many super cars, the BMW i3/i8 & AR 4C production cars have CHASSIS' that are carbon fiber...

The simple question, should GM abandon aluminum and utilize their existing Saturn/vette experience to create composite body panels and/or go all in and get into CF chassis?

Then you have another angle...Body panels are all sprung weight with considerable costs to go from metal to even composite...Unsprung weight is where you maximize your light-weighting...The Ford Mustang GT350R is the first affordable car to offer CF wheels...Here are the differences vs aluminum: http://blog.caranddriver.com/tested-quantifying-the-performance-benefits-of-the-shelby-gt350rs-carbon-fiber-wheels/...While expensive, they're also huge...If you did a 15x6 they'd be much cheaper...There are also CF rotors that could be developed...
 

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Well aluminum is the easy route to weight loss as GM isn't about go the route BMW followed by the i3. One of the cost factors of the i3 is its advanced composite construction. It was an experiment that has paid off in many BMW cars that have followed and will follow. Eventually many manufacturers will have to go this way as hauling 400kg of batteries pretty much defeats decades of weight saving tricks developed by the industry. (hence I don't think big packs are long term solutions)
 
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