Collision repair technicians are seeing many different materials today that make up the outer and inner structures of vehicles. But is this truly a new development, or has it been going on for a while? The answer might surprise you.

The “Original” Hybrids

The fact of the matter is that auto manufacturers have been using various types of materials in vehicle structures for a little over 100 years – since about the time the first automobile was manufactured.

Aluminum was one of the early materials used due to the ease with which it could be formed as the result of being soft-tempered. But it was mostly only used on the classic, expensive luxury cars such as the Pierce Arrow, Duesenberg, Lincoln, Marmon, Packard, Cadillac and others. With so few of those cars being made, hand-forming was more practical than creating stamping dies for steel. It was not practical to hand-form the high-production Model T Fords, however, although many of these early Fords had aluminum hoods because of their light weight.

Many of these luxury car manufacturers had several body makers working for them that crafted special ordered bodies upon request. Murphy, Rollston, LaGrande and Fisher were just a few of the more famous body makers.

These manufacturers were the original hybrid manufacturers. Often, a run of two or three chassis configurations would be used for different bodies, with a shorter chassis for a coupe or two-door sedan and a longer chassis for an extended dual cowl phaeton, town car or limousine.

Onto these custom-made bodies would be mated standard and recognizable front ends and fenders. The bodies would be hand-formed aluminum, while the front ends and fenders were stamped steel because of the higher production numbers. The hoods, which could be long and cumbersome, were often made of aluminum to make them much more manageable to open and close.

There was often wood under the custom-made outer skins to afford rigidity to the body. The wood was often oak but could be ash or another type of hardwood.

Galvanic Corrosion

Were any problems created by mixing these dissimilar materials? Yes. From my 40-plus years in the collision repair industry, I can confidently say that I don’t think the manufacturers gave much thought to the possibility of galvanic corrosion, which results from dissimilar metals coming in contact in the presence of an electrolyte such as moisture in the air or water.

I can’t be completely positive that the automakers were clueless about this potential problem – the problems I saw may well have been repairers’ fault. See, by the time I got my hands on many of these vehicles, they had been repaired here and there, and it may just have been that my fellow body men may not have understood the need for careful reassembly and isolation of the dissimilar metals.

Aluminum, for instance, will corrode much faster in contact with steel than it will by itself, so when the Austin Healeys, Jaguars, MGs and vintage luxury cars got to me, they were usually corroded many times over.

Steel

As automobiles became more and more common, higher production runs became the norm. The industry learned better stamping techniques, which allowed the entire vehicle to be made from steel. This was, of course, faster and cheaper. It didn’t require highly skilled metal men to hand-form the parts.

Steel, although heavier than aluminum, was much cheaper, and fuel efficiency wasn’t an issue since gas was around 25 cents a gallon! All steel bodies were touted as more rigid, and wood was eventually phased out. For approximately 60-plus years, all-steel was the standard for American-made vehicles as well as many high-production European and Japanese vehicles.

Aluminum

Many people in our industry today came into the trade when just about all cars were steel. When aluminum showed up on the scene recently, it was thought of as somewhat exotic. But of course, when we review history, we learn that it has been around in the auto manufacturing industry about as long as steel.

But we’re using aluminum differently than we have in the past, e.g. large castings for not only suspension parts like control arms and knuckles but also in the body of space frame vehicles, such as the Audi A8. Some unibodies also use these cast nodes as receptors or connectors for other parts that fit into them (Photo 1).

Extruded aluminum is also used, which is relatively new in the auto industry. Extrusions and castings are assembled together in the space frame to make an extremely strong, lightweight inner structure (Photo 2). However, the parts have limited repairability.  

Why is aluminum being used now in so many different ways? With gas at nearly $4 a gallon and heading north, reduction in weight is what it’s all about because that saves fuel and thus money for the consumer.

Steel-structure vehicles also use many weight-saving parts made from aluminum such as fenders, hoods, doors, reinforcement bars, hatches and deck lids. This reduces the overall curb weight. Compared to steel, aluminum parts are about 30 percent lighter (Photo 3).

We’ll see more aluminum bolt-on parts on steel vehicles as time goes on, not only because aluminum is lighter but because the more aluminum parts that enter the market, the more aluminum there is to recycle. Recycling aluminum is 75 percent cheaper than smelting from virgin ore. This gives manufacturers more incentive to use these parts.

Some people think that aluminum can be easily dented, but it’s actually more dent resistant than steel the way it’s used by most manufacturers. The aluminum bolt-on body parts are repairable with the proper technique – which is a lot different than repairing steel. Most aluminum bolt-on body parts that are damaged should be heated between 400° F and 570° F prior to removing the damage (Photo 4).

You should get the proper training prior to working aluminum. I-CAR has a great aluminum repair series, and I suggest starting with STA01 for straightening aluminum.

Magnesium

The modern vehicle employs more elements than just steel and aluminum. Try magnesium, for instance. Why? Once again, we come back to what the automotive engineer is trying to accomplish.

On average, the new model vehicle is 400 lbs. heavier than its predecessor. Hard to believe, isn’t it? I’m actually working on these cars every day, and their construction seems much lighter than previous models. So what gives? It’s called gadgetry. It isn’t so much the construction of the vehicle making them heavier as it is what we’re adding to it. Huh? Yeah, that’s right…all those airbags, computers, cameras, infotainment systems, etc.

As the OEs have lightened up the vehicles with advanced materials and advanced vehicle design, they’ve loaded in heavy electronic gear. So far, we’re losing this Battle of the Bulge, and even more advanced materials are entering the war on weight gain. Magnesium is one of the increasingly used elements in this struggle for weight control.

Why magnesium? It’s a lightweight material that’s stronger and lighter than some steels and thus is good for casting. Plus, it doesn’t convey sound the way steel does, so it’s a good noise, vibration and harshness deterrent. A bonus is that it’s plentiful in the earth’s surface, so it’s readily available.

There are many parts on a modern vehicle made from magnesium…and its use is expanding. Most of it is used in castings, such as the Ford F-150 pick-up (Photo 5) radiator support, Chevrolet Corvette ZR1 engine cradle and suspension crossmembers, and door frames on the Lincoln MKT and some Mercedes models. It’s also found in instrument panel frames on some GM models, and steering wheels and seat frames on other various vehicles.

Magnesium parts aren’t generally repairable, although Ford allows some limited repair on its F-150 radiator support. Most castings offer only limited repair possibilities. Generally, these parts use mechanical fasteners (bolts, rivets, etc.). Galvanic corrosion is always a consideration in vehicles constructed of various metals, so follow the manufacturer’s specific recommended steps for preventing corrosion failure when replacing magnesium parts.

Most of you might have heard about how magnesium burns uncontrollably once ignited. This is true, but your chance of igniting it is remote. It isn’t weldable in a collision repair setting, so don’t even try because you won’t be able to. Also, don’t try to heat it with an oxyacetylene torch. There isn’t any reason to, and even if you did have a reason, you would find it difficult to ignite. I know this because, of course, like a mischievous kid, I had to see what all the rampant fear was about.  

Here’s what I learned: Igniting anything larger than a 1/2-inch by 1/2-inch by 1/4-inch chunk would take a lot of intense, continued, focused heat. Once it does begin to burn, it emits a bright greenish fire that has to be smothered with something like sand. Water won’t work! If you take a file to a magnesium casting and gather the filings in a small pile, they’ll readily ignite when applying a torch. The smaller the magnesium, the more ignitable it is. This is some of what’s inside the fireworks we see in the sky on the Fourth of July, and different metal filings provide different colors. Cool, huh?

Carbon Fiber

Carbon fiber is fairly new to the OE manufacturing process, although we’ve seen it in the aftermarket for a number of years as hoods, flares, decklids and trim pieces. Its popularity in the aftermarket comes from its unique woven design. Street racers have created a market that makes them look cool.

The aircraft industry is big in my city of Seattle, with Boeing being the largest manufacturer in the state. They’ve invested in carbon fiber big-time with their new Dreamliner plane, using it as a replacement for aluminum. Even though the company has had some major problems and setbacks with this new project, it remains committed to carbon fiber as it forges ahead into completely new manufacturing processes. The automobile industry is headed in the same direction with these advanced materials.

To be accurate, carbon fiber is properly called carbon fiber reinforced composite (Photo 6). What makes it different from sheet molded compound (SMC) or fiberglass (FRP)? It’s a combination of carbon fibers and a polymer resin. The fibers are formed by joining carbon atoms together to create strands. Those strands are then woven together to form a material that’s combined with a resin to form a very strong, lightweight substance. The substance is placed in forms, molds and dies in its uncured state to make car parts. Degradation due to ultraviolet rays is overcome by the addition of a UV arrester (which costs $60,000 a gallon!) in the resin.

While the very basic process and outcome may be similar to SMC or fiberglass, that’s where the similarity ends. Carbon fiber is very strong and lightweight – as strong as, or stronger than, similar parts made from steel or aluminum. Auto manufacturers use it when they need exceptional strength but light weight. Neither fiberglass nor SMC offer these two requirements together. It’s also very rigid, which is useful when the OE has a high weight-to-stiffness requirement.

In the exposed weave (as opposed to non-visible weave) application, the patterns vary. Some vehicles like Corvette and BMW have exposed weave exterior parts such as hoods, flares, tops and trim. These parts offer limited repairability due to the matching of the weave pattern. Some relatively minor refinish work may be done using conventional refinishing clearcoats or manufacturer-specific clearcoats, depending on the OE recommendations.

Repairs to non-visible weave carbon fiber are sometimes possible because these parts are painted.  However, if the damage extends to the edge of the part, it can’t be repaired. Access to the backside of the part will also be a consideration with a two-sided repair. Always verify repairability of these parts by checking OE recommendations. Some OEs don’t recommend repair of carbon fiber whatsoever.

Carbon fiber has its hazards, too. Grinding it will expose you to airborne dust, which can cause ulcers to the eyes and respiratory issues. Protect yourself with the correct equipment, tools and information to do the repair safely and correctly.  

Also, galvanic corrosion is an issue with carbon fiber. Make sure to vacuum the dust and excess material from cavities in the body of the vehicle to prevent corrosion.

Corvette uses carbon fiber in the top, floor pan, fenders and hood. BMW uses a carbon fiber top on the M6, and the Mercedes-Benz SLR has carbon fiber door panels. The radiator core support and floor closure panels on the Nissan GTR are carbon fiber. Some exotics like Ferrari and Aston Martin, as well as Mercedes-Benz, are using carbon fiber in the structure of their exclusive models.

Where Are We Headed?

It’s difficult to predict what the future holds but one thing is constant: the need for training. Check out the following I-CAR courses: STA01, NEW10, NEW11, DAM05, DAM08 and PLA03.

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Writer Mike West, a contributing editor to BodyShop Business, has been a shop owner for more than 30 years and a technician for more than 40 years. His shop in Seattle, Wash., has attained the I-CAR Gold Class distinction and the ASE Blue Seal of Excellence.