Magnesium in Automobiles – Smart car sparkles

In November of 2016 I wrote about the dangers of the use of magnesium in automotive applications. While the article is currently not available due to the still incomplete site update, in has been mentioned in other publications, such as The Drive and GM Authority. I also posted a version of it below. Despite lots of research and substantiated facts within the article, I caught a lot of shit for it. First ones to deny any potential of danger were the automakers. Then people who took high school chemistry ripped me a new one. One so-called lawyer, racer, and social media alpha-male-wanna-be said it was as clickbait. I question if any of those people actually read it.

In May of 2018, the entire production of the Ford F-150 briefly stopped. The reason for it was an explosion (!) at one of its suppliers, Meridian Magnesium Products of America. This company was the sole-supplier of magnesium instrument panel components for those trucks. The explosion injured two employees and started a fire that raged for a considerable amount of time. Ford brilliantly turned this into a marketing opportunity, but that’s another story.

Recently, I was browsing the news. An article from Warsaw, Poland, showed a car fire. Following a minor collision, a Smart ForTwo was fully engorged in fire on the side of the road. Due to the amount of time it took to put the fire out, and entire three-lane artery was closed for some time. The Smart ForTwo’s engine has magnesium components.

The atypical sparks seen in the picture above are the result of water being poured onto burning magnesium. A magnesium fire burns at a very high temperature, significantly over 5,000°F. That is enough to not only melt steel, aluminum, and iron but also to break down water to its basic elements of oxygen and hydrogen. Hydrogen is a highly-flammable gas. When exposed to the burning magnesium, the gas ignites, further enraging the fire, making magnesium fires very difficult to extinguish.

Combustible metal fires are known as Class D fires. They are best extinguished with sand or dry powders. Water can extinguish it, as long as it is extensive amounts. Cass D fire extinguishers exist but they are ineffective on all other classes of fires and therefore not frequently, or in large quantities, carried by fire departments.

There is good news! Ignition of a solid magnesium structure, unlike magnesium shavings, requires a lot of energy. Chances are that your vehicle is already burning out of control before the magnesium components ignite, and hopefully its occupants have managed to get out before that. Production of magnesium components, especially where shavings are present is a different story.

 

Below is a copy of my November 2016 Hooniverse article on Magnesium fires in cars:

The Use of Magnesium in Automobiles – Corvette Fender-Bender Leads to a Meltdown

Pictured above are remains of a sixth generation (2005 – 2013) Chevrolet Corvette Z06. The vehicle was involved in what was described as a minor fender-bender on I-90, also known as the Massachusetts Turnpike, in Newton, Massachusetts, on June 13, 2016. No one was hurt and the other car had trim damage and was drivable. Likewise, the Corvette seemed to have sustained just minor damage until its owner noticed an under-hood fire.

In design of the C6 Z06 several weight saving measures were taken to lower its curb weight, most significantly a switch to an aluminum frame. Floors were made of balsa wood and carbon-fiber composite. Under the hood, the Z06 had a huge 7.0-liter LS7 engine with a dry-sump oiling system. To lower the weight in the front of the vehicle, under the engine, the front sub-frame was made out of magnesium.

Image source

Magnesium and Aluminum are one atomic number apart yet fit into different groups on the periodic table of elements. Both are abundant in the universe and easily formed or molded. Magnesium alloys are thirty percent lighter than aluminum and fifty percent lighter than steel, but not as dense or strong as either of those metals. Over time automakers have developed specific applications for each of those metals. A big limiting factor of magnesium uses are the metal’s flammable properties.

Ignition of a solid magnesium structure, unlike magnesium shavings, requires a lot of energy. Once ignited, however, it burns at a very high temperature, significantly over 5,000°F. That is enough to not only melt steel, aluminum, and iron but also to break down water to its basic elements of oxygen and hydrogen. Hydrogen is a highly-flammable gas. When exposed to the burning magnesium, the gas ignites, further enraging the fire, making magnesium fires very difficult to extinguish with insufficient amount of water. Further, common carbon dioxide (CO2) fire extinguishers will also react violently.

Combustible metal fires are known as Class D fires. The best way to extinguish a class D fire, such as a magnesium fire, is with sand or other dry powders. There are Class D fire extinguishers but they are ineffective on all other classes of fires and therefore not frequently, or in large quantities, carried by fire departments.

Image source: @the_ZH-Twitter

Just about all automakers use magnesium in their vehicles. In the current, seventh generation Corvette, General Motors uses magnesium in the Corvette’s steering column support, seat frames, and in the front sub-frame (Z06 only), all in the name of weight reduction. General Motors’ other vehicles have steering columns, steering wheels, and transfers cases made of the metal. The full-size Chevy Express and GMC Savana vans have magnesium instrument panels, GM’s biggest magnesium part.

Porsche has probably been using magnesium the longest and currently uses the metal in the Panamera door frames and the frame of the 911 Cabriolet’s roof. The track orientated Porsche 911 GT3 RS has a magnesium roof. Porsche chose magnesium over carbon fiber in this instance because exterior body parts often do not meet the theoretically possible level of weight savings. This is because additional surface films and paint coats are necessary to achieve the desired surface finish. Further, Porsche’s Product Experience Manager, Frank Wiesmann, says that “the high cost of carbon fiber and the high amount of effort regarding the production and paint process in multiple steps, including several levels of polishing, result in carbon fiber pieces for the exterior being very expensive. The magnesium roof is cheaper than a comparable carbon fiber roof, and it is also an estimated 700 grams or 24 percent lighter.”

Chrysler proudly points out that their new Pacifica minivan “will have the highest-volume application of a die-cast Mg closure on the market.” Chrysler is also quick to emphasize that “the material used in the Pacifica’s lift gate inner panel is an alloy, of which magnesium is the primary component. Regardless, magnesium in this form does not pose an ignition risk.  Accordingly, vehicles that contain magnesium benefit from significant weight reduction. The material is commonly used in steering wheel armatures and instrument panel cross-car beams. The Dodge Viper’s cast magnesium dashboard structure is the largest single piece of magnesium in any production car in the world.”

Image source: columbian.com

The Code of Federal Regulations, Chapter 49, states the standards for vehicle flammability, but those are limited only to interior materials. The CFR does not mention anything directly that could be found regarding combustibility of chassis metals. There are however many first responder resources on how to deal with flammable metals, hybrid batteries, electrical propulsion, airbags and airbag inflators, and many other components currently incorporated into automobiles.

The Society of Automotive Engineers (SAE) develops standards for both the automotive and aviation industries. On August 14, 2015, the SAE published SAE AS8049 Revision C. The revision to the document was based on the Federal Aviation Administration’s Technical Standard Order (TSO) FAA TSO-C127b, a minimum performance standard. SAE AS8049 Revision C replaced “Magnesium alloys shall not be used” wording regarding seat frames with “Magnesium alloys may be used in aircraft seat construction provided they are tested to and meet the flammability performance requirements in the FAA Fire Safety Branch document: Aircraft Materials Fire Test Handbook – DOT/FAA/AR-00/12, Chapter 25, Oil Burner Flammability Test for Magnesium Alloy Seat Structure.” In its testing, the FAA found that the aircraft grade magnesium alloy materials used for seat frames performed as well or better than aluminum. Magnesium is widely used in jet engines, landing gear, and other forged components.

Car fires are not uncommon and, despite what WreckedExotics.com shows, no one vehicle is more susceptive than any other. The U.S. Fire Administration reports that there was an average of 210,000 car fires per year over the last ten years, or over 575 per day. There is no one determination to the causes of these fires but it should be no surprise that the delicate balance of a very hot engine, electronics, and flammable liquids all cramped into the engine bay can be easily upset in the smallest of accidents. The good news from the administration is that the number of cars fires has been declining over the years.

It is unknown what specifically started the fire in this Corvette but it quickly engulfed the whole car sending dramatic smoke high up into the morning New England sky. When the fire department arrived they had surprising difficulty putting the fire completely out. Pooling of melted metal, which was on fire, believed to be magnesium was observed under the car. The fire department used two tanks of water, over 1000 gallons, and class B foam to finally put it out. That is about twice as much as on a conventional car fire.

Each year automakers are being forced to make more economical cars, which is best accomplished by weight reduction. The use of magnesium alloys in automobiles will therefore likely continue to increase. Magnesium has lower manufacturing costs than aluminum but with increased production, material costs are likely to go down. Magnesium’s only downside seems to be its flammability property, which automakers insist is not an issue in automotive applications.

14 Comments

  1. That Corvette pic… all I can see is that the “Mag” wheels were the only thing that didn’t burn!

    I know trolls be trollin’, but I can’t find any strong opinion one way or the other in either of your posts. They just state facts that boil down to, “There’s a lot more magnesium in cars these days” and “magnesium is wicked flammable”; the danger being more in the manufacturing end The only things I’d add is that aluminum has a burn rate, too, but I’m guessing it’s slower and not as hot (guessing!) As you touched on, if you can’t get out of your car before the magnesium ignites, you’re probably dead from smoke inhalation already.

    If you make everything out of carbon fiber, someone’s gonna complain that it shatters into saw blade-like edges, or that it’s an environmental burden to make and dispose of. I think we’ve pushed aluminum about as far as it can go, and that’s why magnesium is the new aluminum.

    1. I think the difference with aluminium is that it doesn’t burn hot enough to split water into a flammable H2 & O2 mix: So although it burns hot, the standard firefighting medium carried by any first-responding fire truck (water) will still be effective rather than exacerbating the fire.

      A single car on fire on the open road is not really the big problem here; the occupants should be safely away and firefighters can — if need be — just stand off and watch it burn out.
      More worrying is the effect of exotic materials — and emerging powertrains — on vehicle fires in confined spaces; say tunnels, parking structures or ro-ro ferries: A lot of things (including standard fire-fighting practices, building design codes and even insurance rates) are based on the assumptions of relatively slow fire spread and simple means of intervention (sprinklers, ventilation fans etc.) being sufficient to bring the fire under control and extinguish it.
      Now imagine a whole level of an underground garage filled up with Corvettes and/or Smart cars: Instead of a relatively slow spread of an established fire from one vehicle to the next, materials burning at much higher temperatures could cause secondary fires to start in a much wider radius. Automatic sprinkler discharge could make the fire worse. Peak temperatures and fire growth curves could be very different from those used as the basis of design for steel-or concrete-framed buildings (all based on cellulose or hydrocarbon fire models).

      (In a recent fire in the UK over 1,000 vehicles were destroyed in a multi-storey (above ground!) car park fire. https://www.bbc.co.uk/news/uk-england-merseyside-42542556)

      https://ichef.bbci.co.uk/news/976/cpsprodpb/6633/production/_99436162_carparkfireinside2merseyfire.jpg

    2. The problem is with extinguishing the fiercely burning fires.
      Fires, hot air, etc go up from its source. Wheels are typically lower and further to the side, which is why often they’re the only thing left standing.

      1. As a firefighter in the US, we are taught in entry level training the dangers of fighting car fires in cars with magnesium components. If the magnesium is burning, initial application of water can be expected to cause reactions as the one shown above. Large quantities of water can overcome and extinguish the burning magnesium, but the process will be violent and should be done from a distance. Disclaimer: I have not personally been on a car fire involving magnesium. Just what I’ve been taught.

        Also, the American and European fire services have a very big difference- the US typically uses (relatively) low pressure/high volume streams. Europeans typically use (relatively) low volume/high pressure streams. Meaning the standard American hose line is more likely to quickly provide a quantity of water sufficient to overcome those reactions, and the European lines may take a little longer and be more dramatic (see above) in the process.

        1. Good to know that distinction.

          As far as Monkey10is concern about emerging powertrains, I can comment on Lithium Ion packs:
          When one goes into runaway, it’s not a combustion problem, it’s a heat problem.
          Combustion is just a side effect of the heat energy being released.
          The only solution is a massive volume of water (with its unmatched heat capacity.)
          Don’t mess around with foam or CO2. (The FAA and I disagree on this one, though we agree that pure water is a solution.)
          Literally the safest thing to do is dump it in a pool. (The FAA and I agree on this one.)

          You can put out the flames, but if a short or puncture is still releasing energy, it’s going to get hot and reignite again.
          ICE is an insulator, so a pack tossed in ice is very likely to self-heat and re-ignite. (The FAA taught me this.)

          Remember: The chemistry is Lithium-ION, not elemental lithium.
          The tiny amount of pure lithium that might (and probably won’t) react with the water is a decimal rounding error compared to the chemical and electrical energy that needs to be absorbed.
          You can find a few videos of people tossing a hot pack into a bucket, and then it explodes.
          The explosion is the same one you can see when they’re set off while high and dry.
          Anyone who tosses a pack in a bucket of water is lucky the water is there to dampen the burst (no pun intended.)

          Notes:
          1. The bigger the individual cell, the bigger the individual release, the harder it is to stop it from propagating to other cells.
          2. Runaway energy release from electrical and chemical energy is ~= 2X charge.
          2a. In other words, a fully charged 3Wh cell runaway ~=6Wh, a 20% charge 3Wh cell runaway = 1.2Wh.
          3. If you make custom packs, having a regular, safe, EVERY SINGLE TIME discharge procedure for storage greatly reduces the chances of a big thermal event.
          3a. A custom pack should be charging or fully charged for immediate use only.
          3b. Safe maximum discharge levels will usually be 20-30%.
          3d. This makes it a lot harder for one runaway cell to put its neighbors into runaway.
          4. Have a nearby volume of water for extinguishing/cooling.
          4a. The order of magnitude for a 100kWh pack starts around 5000L.

        2. Good to know that distinction.

          As far as Monkey10is concern about emerging powertrains, I can comment on Lithium Ion packs:
          When one goes into runaway, it’s not a combustion problem, it’s a heat problem.
          Combustion is just a side effect of the heat energy being released.
          The only solution is a massive volume of water (with its unmatched heat capacity.)
          Don’t mess around with foam or CO2. (The FAA and I disagree on this one, though we agree that pure water is a solution.)
          Literally the safest thing to do is dump it in a pool. (The FAA and I agree on this one.)

          You can put out the flames, but if a short or puncture is still releasing energy, it’s going to get hot and reignite again.
          ICE is an insulator, so a pack tossed in ice is very likely to self-heat and re-ignite. (The FAA taught me this.)

          Remember: The chemistry is Lithium-ION, not elemental lithium.
          The tiny amount of pure lithium that might (and probably won’t) react with the water is a decimal rounding error compared to the chemical and electrical energy that needs to be absorbed.
          You can find a few videos of people tossing a hot pack into a bucket, and then it explodes.
          The explosion is the same one you can see when they’re set off while high and dry.
          Anyone who tosses a pack in a bucket of water is lucky the water is there to dampen the burst (no pun intended.)

          Notes:
          1. The bigger the individual cell, the bigger the individual release, the harder it is to stop it from propagating to other cells.
          2. Runaway energy release from electrical and chemical energy is ~= 2X charge.
          2a. In other words, a fully charged 3Wh cell runaway ~=6Wh, a 20% charge 3Wh cell runaway = 1.2Wh.
          3. If you make custom packs, having a regular, safe, EVERY SINGLE TIME discharge procedure for storage greatly reduces the chances of a big thermal event.
          3a. A custom pack should be charging or fully charged for immediate use only.
          3b. Safe maximum discharge levels will usually be 20-30%.
          3d. This makes it a lot harder for one runaway cell to put its neighbors into runaway.
          4. Have a nearby volume of water for extinguishing/cooling.
          4a. The order of magnitude for a 100kWh pack starts around 5000L.

    3. Carbon Fibre can be recycled by the way, which was Zenos Cars business plan really. Make Caterham alternatives that use recycled carbon fibre. Business didn’t work out, though that is pretty common in the endless merry-go-round of UK cottage industry sports car companies. It probably should be seen as just another sportscar company that didn’t work out rather than the core idea of the car not being sound. It had a lot of potential, but needed to iron out the kinks, and probably make a version with at least a windscreen and proper weather protection. Remember the original Ariel Atom was a bit of a dog when it came out too. Some companies hang on long enough to sort the product out, some don’t. For every Ginetta and Lotus, there’s hundreds of forgotten uk sportscar/kit makers.

      I don’t know if Magnesium deserves its bad rap, but two things strike me..

      1. Isn’t there a reason we stopped using “mag” wheels and different alloys instead? (perhaps only for cost/maintenance?)
      2. If we need to make cars lighter, which I’d argue we do, why are we sticking with the mostly pressed steel or aluminium monocoque method of construction? Surely that’s met its limit and other ways of building cars should be looked at? I mean there’s Gordon Murrays iStream process, and BMW has that whole CFRP reinvention of body on frame with the i3 but doesn’t seem to entirely incorporate those ideas into its mainstream cars? It seems to me that it no longer meets the future demands of how cars should go. i.e. light, can be made in small volumes locally economically, and ideally, should be cheaper to make than now.

    1. Years ago I was told a story about some guys who put a VW engine on a fire and it burnt through a concrete slab

      1. Guys I knew used to take a VW engine block to throw on the campfire every time they went up Fraser Island. They said it would melt the sand underneath.

  2. I have to admit, dull witted as I am known to be, I just can’t get too concerned about this as an existential threat. Yes, magnesium catches on fire and burns ferociously when it does. However, the existence of some 23 million Volkswagen engines made over a 50 year period created no epidemic of magnesium fires. Almost everyone over 50 will have known of at least one Volkswagen, but how many are aware of a Beetle whose engine caught on fire and the magnesium case burned? If any magnesium part seems like a good candidate for catching fire, I think an air cooled engine filled with fuel would be one. I admit that I have OEM magnesium wheels on my 71 Alfa, so I am perhaps biased but I’m more concerned about those wheels cracking and breaking than about them catching fire.

    Of course, I am certainly willing to admit that I may be wrong not to worry about magnesium when Smarts are catching fire. I have been known to do stupid and dangerous things, up to and including disabling that freaking auto shut-off on my lawn mower.
    EDIT
    I usually try to avoid using Wikipedia as a source, but since it supports my position, I’ll just leave this here.

    “A common misconception persists regarding the danger caused by magnesium’s flammability. But new improved alloys have been developed over the past fifty years, with no reportable incidents of magnesium wheels catching fire. In fact, the U.S. Federal Aviation Administration has conducted wide-ranging tests over the past decade, concluding that the potential flammability of magnesium is no longer a concern—and even ruling to allow its use in aircraft cabins.[4]”

    https://en.m.wikipedia.org/wiki/Magnesium_wheels

    [4] =https://www.fire.tc.faa.gov/pdf/ar11-13.pdf

    https://browse.startpage.com/do/show_picture.pl?l=english&rais=1&oiu=http%3A%2F%2F1.bp.blogspot.com%2F-35gvPLi_fGU%2FUAUOgRnwOLI%2FAAAAAAAAGEA%2FJ595_oBAtcw%2Fs640%2FHdhut.blogspot.com%2B%252817%2529.jpg&sp=d59405c6c4b8612857382ae4f1606b4d&rl=NONE&t=default

  3. I hadn’t thought of the fire hazard of magnesium car parts,although I should have since Pierre Levegh’s 1955 Le Mans crash was exacerbated by the subsequent magnesium fire. One of the other issues is cost of repair, when the 2004-2008 Ford F-150 came out, people discovered that the magnesium radiator support was extremely expensive to replace if damaged.

    To answer crank_case, one reason magnesium wheels fell out favor for street use is corrosion, since magnesium is more susceptible than aluminum. A good example is Dymag motorcycle wheels, which are available in magnesium for racing and aluminum for street use.

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