Aluminum Use on U.S. Vehicles

Aluminum Use on U.S. Vehicles – The Shape of Things to Come

Adapted from Mike West's feature in BodyShop Business

Aluminum has been employed since the early days of the automobile. And I’m not talking about some obscure gadget on an unheard-of car that history forgot, either. You’ve all heard of the Model T Ford – and most of us even know what one looks like. But did you know that the hood on a Model T Ford was made of aluminum?

This is a car that Ford literally produced millions of – and its last year of production was 1927. Many luxury automobiles of limited production also used aluminum because of its easy-to-form characteristics, and many pre-1930s vehicles were completely made from aluminum. Pierce-Arrow automobiles had models that employed aluminum castings to make up the body structure, as well as aluminum engines.

My point here is, the American automobile industry used aluminum extensively, especially in the early years, and we know that aluminum has been repaired at least as long as it’s been used in the automobile. And that’s a long time. Which is why I’m a little amused by all the hub-bub about the “dawning of the new age of collision repair.”

Don’t get me wrong. I’m not trying to minimize the difference in repairing steel and aluminum. There are differences, just like repairing plastic composites is different from repairing steel. (In fact, those differences are greater than aluminum and steel because plastic composites aren’t metals.) But as they say in the aluminum industry, “Repairing aluminum isn’t difficult … just different.”

What Happened To Aluminum?

If aluminum was so great in the first place, why did the auto manufacturers shift more and more to steel? Just like everything in manufacturing, it’s based on economics. As auto manufacturers became bigger and bigger, steel became a more efficient and cheaper metal to make automobiles out of. Sheet steel stamping was a major advance in production over hand forming because stamping produced a consistency that went hand-in-hand with the assembly line. And obviously, weight wasn’t a big factor when gasoline was 25 cents a gallon – or even 50 or 75 cents a gallon. It wasn’t unusual for automobiles to tip the scales at 3 tons or more!

But things today are just a little bit different. A couple of months ago, I was pumping gas into my red Dodge pickup for $2.09 cents a gallon. Nasty! Those $40 fillups tend to cause the mind to consider more fuel-efficient technology and lighter vehicles.

Size Does Matter

The auto industry has known for a long time that the lighter a car is, the more fuel-efficient it is. And the more fuel-efficient it is, the less pollution it produces. But I was around when the first Chevy Citation showed up, and we were told that this unibody was the wave of the future. Hmmm … So how come shops are full of Suburbans, Durangos, Expeditions and Siennas?

I guess Americans don’t really like those econoboxes – at least not enough to buy them. And we’ve proven to ourselves that getting smaller isn’t going to do it. Americans don’t seem to want to buy such small cars. So can we stay at a reasonable size (by American standards) and still be fuel-efficient?

If we build lighter, we probably can. And it’s easier to achieve fuel efficiency through “lightweighting” than it is through rolling resistance or aerodynamics.

Gaining Weight

Consider the 1975 VW Golf S, which weighed 780 kg. Then there’s the 1998 Golf, which weighed 1,090 kg. Face it, we’re not getting lighter. We’re cramming more electronics and other systems into these vehicles because the car-buying public loves it.

Aluminum Bounces Back

Ok – re-enter aluminum into the equation. It’s four times lighter and six times stronger than steel. What!! Six times stronger than steel? Yep. Aluminum in its alloyed forms and tempers is up to six times stronger than steel.

Not only that, but consider that aluminum is one of the most plentiful elements on earth. It’s everywhere, and when it’s scrapped and recycled, it takes only 5% of the original energy it took to initially form it the first time – and with no loss of quality. This is a huge consideration because aluminum can be recycled at low energy consumption and be extremely environmentally friendly.

Take plastic composites for example: Look in your school’s dumpster. What do you see? A bunch of plastic that doesn’t decompose, that’s got a petroleum base, that’s being landfilled and that no good recycling scheme has been engineered for. Wow, sounds kind of shortsighted to me.

The current model-year average American car uses 274 pounds of aluminum. By the year 2015, we should be at 441 pounds per car, according to industry experts. Currently, 80% of our automotive use is in castings, with 6% in extrusions. That leaves 14% for other uses, such as body parts.

Compare the annual U.S. automotive aluminum usage of 3.2 billion pounds to Europe’s 5.5 billion pounds. The Europeans are clearly ahead of us in aluminum consumption – for several reasons: Gas is much more expensive in Europe, pollution is a bigger problem with large tracts of forests dying from acid rain and European governments are mandating recyclability for the automakers prior to production.

We may be behind, but we’re not out of the running. In my practical opinion, we’re going to work with aluminum more and more in the future. It makes sense.

It also makes sense that if aluminum really is the “metal of the future,” then we need to learn to work with it and repair it. First, let me say this: I enjoy working with aluminum. I like it. And if you start out with a positive attitude and a good outlook, success will be yours.

Corrosion Concerns

Galvanic corrosion is an 800-pound gorilla when you’re working with aluminum. You must pay careful attention to avoid cross-pollution of steel and aluminum in the repair process.

“What in the *#%@ is he talking about now?” you ask.

Look, I know most of you aren’t chemists or metallurgists. Neither am I. So let’s approach it in layman’s terms: Don’t allow any steel dust, grindings, sparks, residue or anything like sanding disks or papers that have been used on steel to come in contact with aluminum. If you do and you paint over it, you’ll be redoing it because corrosion will occur.

This issue is so serious that Audi recommends a separate repair facility with its own tools specifically for their aluminum-bodied vehicles. Think they’d do that if there weren’t potential for corrosion?

Many – or most – of you aren’t going to set up a separate repair facility to repair a vehicle with some aluminum parts or even an aluminum-intensive vehicle like the Audi A8 or Jaguar XJ. You do, however, need to give every consideration to each possibility of potential cross-pollution and make every effort to prevent it from happening.

Eliminate Galvanic Corrosion

  1. Place your aluminum vehicle away from steel vehicles where grinding, sanding, welding or other intensive repairs are taking place.
  2. Clean the jaws of your clamps thoroughly before and after use on aluminum. Upon removal of the clamp, wire brush (using a stainless steel wire brush dedicated to aluminum) in the area that was clamped. This is done because there could be some steel deposits imbedded in the aluminum from the clamp.
  3. Clean all your hammers, dollies, files, pry bars and etc., before using on aluminum. You may want to consider a separate set of commonly used hand tools, kept in a small box, to be dedicated to aluminum only.
  4. Clean sanding and grinding tools thoroughly (wipe down and vacuum or air blow) prior to use on aluminum.
  5. Always use new sanding discs and sandpaper to avoid cross pollution.

The Good, The Bad and the Ugly

Oxidation is a 750-pound gorilla in aluminum repair. It’s a tiny bit smaller than galvanic corrosion, but it’s still way too big to ignore. (If you do ignore it, you’re going to get hurt … financially.)

Aluminum oxidation is both a good thing and a bad thing. It’s good because when the oxidation layer forms on aluminum, it produces a protective coating that prevents the base metal from corroding. It’s bad because paint, fillers and the welding process are seriously compromised unless this oxidation layer is removed first. This makes for an ugly re-do.

Thing is, it’s invisible to the naked eye in its initial stages, which makes removal all the more important. Coatings don’t stick to oxidation!

How quickly will aluminum oxidation begin to form? The atmospheric climate is a big determiner, but I wouldn’t prime over sanded and treated aluminum after two hours without repeating the process again. Follow your paint manufacturer’s recommendations for your local area.

Immediately prior to welding aluminum, you should always wire brush all your weld areas with a clean, stainless steel wire brush dedicated to aluminum only.

Get it Hot

Most body panels are tempered or work hardened to add dent resistance or strength to the part. Depending on the size of the dent, it may be necessary to heat the repair area to bring the damage out to its original contour. Because aluminum readily work hardens when deformed, it’ll want to stay in its deformed shape. This is true of both heat-treatable and non-heat-treatable aluminum. They both can be heated to aid in reformation.

Much care should be taken to determine the temperature of the aluminum, to allow forming. Between 400 F and 570 F is the workability range of aluminum. You’ll anneal aluminum in the 700+ F range and lose the strength that was engineered into it. (It’ll become very soft and remain that way when it cools.) This is why you need to be careful not to exceed the 570 F range. Aluminum melts at 1,200 F, but oxide doesn’t burn off until 2,300 F, which is why you need to remove the oxide prior to welding.

All of this occurs with no perceptible change in color of the base metal!

Heat Indicator Methods

  1. Heat indicator crayons (available from your welding supplier).
  2. Digital thermometer (racers use these for tire temp readings).
  3. Laser thermometer gun (point shoot-digital reading appears).
  4. Carbon burn-off applied with straight acetylene.

All of these are pretty self-explanatory, except for the old carbon burn-off method. This is a method I’ve used for many years with great success. Turn only the acetylene side of your oxy-acetylene torch on and light it. Turn your gas down at the torch until you have black carbon smoke tailing off the flame. Black off your repair area, and then add oxygen until you have a long feathered heating flame. Warm the panel until the carbon begins to disappear. I checked this with a laser gun thermometer that had been calibrated, and it was 429 degrees F – just right for working.

Methods of heating will vary with accessibility. Heat induction has been used, but you really should use a machine that’s intended to heat aluminum since some heat inductors don’t work well on aluminum. Test before purchasing.

Oxy-acetylene works well with careful attention to heat. Areas that are adhesive bonded to the inner structure for strength require care and attention. You can also use propane.

Keep in mind that aluminum rapidly dissipates heat, so it’ll cool very rapidly and transfer heat to the surrounding area with great speed. Monitor your heat!

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