The Protection of Skid Plates – Aluminum vs Steel!


If you do any kind of rock crawling or drive your off-road truck or Jeep over rougher terrain, it's important that you protect the underside of your vehicle in the same way that you add custom bumpers.

That's where all the critical components other than the engine is located. Skin plates were specifically designed to protect this area.

One big question many off-roaders have about these plates is whether to buy aluminum or steel, which is the same question asked when looking at aftermarket bumpers.

Common sense might say to buy steel because it’s stronger; however, steel weighs more and weight is always an issue when you're upgrading any off-road truck.

Are aluminum skid plates strong enough to be protective? The answer may surprise you.

Aluminum vs. Steel Skid Plates - It’s All in the Construction

A skid plate is a skid plate, right? Well, yes and no.

While all skid plates perform the same basic function, the material they are made from and how they are constructed dictates a lot about what you can expect from yours and how they should be used.

Whether they are made from aluminum or steel, there are shortcomings with each type.

Choosing the best one requires looking into how they are made and the engineering properties of each metal.

Engineering Properties and Skid Plate Strength

To understand how both aluminum and steel can be protective as off-road skid plates, it’s important to look into the properties of the metals, which generally affects how they are constructed.

The main properties to consider when using either steel or aluminum for anything including aftermarket bumpers are:

===>Hardness and Stiffness - Measured with a Mohs scale, steel is more than twice the hardness of aluminum at the same thickness and nearly three times stiffer than aluminum.

===>Strength - Strength is a metal’s ability to yield to impact before it becomes permanently deformed.

While both metals are nearly equal in sheer strength, same thickness of steel are much stronger than aluminum when it comes to impact/yield strength

===>Structural Design - Beyond the actual hardness, stiffness, and strength of the two metals, structural design plays an equally important part in determining how each will perform when used for skid plates.

Aluminum actually has a much greater structural efficiency rating by weight than steel; it can technically be stronger and perform better when the structural design is correct.

===>Corrosion Concerns - Both metals will eventually corrode; steel has a higher corrosion factor and can start to corrode once first scratches are made in the metal similar to when that happens on custom bumpers.

Steel skid plates must be protected by paint and constantly repainted or touched up to preserve them; so faster corrosion that affects the structural integrity of the skid plate is a primary concern with steel.

In damaged areas, aluminum corrodes more slowly and becomes self-containing to produce an oxide barrier on the metal that retards any further corrosion.

No painting or touching up is required.

===>Weight Concerns - Steel is heavier than aluminum; if adding skid plates to an off-road vehicle and overall weight is a concern, aluminum would be the preferred choice.

If you do choose aluminum, you must take the above limitations into account.

Aluminum vs. Steel - What Does It All Mean?

Like those custom bumpers you want to add, the best skid plate for the job is going to depend on a number of things:

===>Thickness - In greater thicknesses, aluminum has been found to be just as strong if not stronger than standard thicknesses of steel.

For this reason, most steel skid plates are produced at 3/16” thickness while aluminum plates are produced at ¼” or greater.

If clearance is not an issue, you can gain all the benefits of aluminum without too much concern about strength by simply purchasing thicker plates.

===>Design - Structural integrity is also maintained with the right design that reduces deflection based on the metal used will maintain such integrity.

Aluminum skid plates require a design that’s been tested for reducing deflection.

===>Use - What you plan to do with your Jeep such as adding aftermarket bumpers also matters; in most cases, properly designed aluminum skid plates are just as reliable as steel.

For extreme use and the strongest protection, steel is best.

If you choose steel based on your needs, be aware that you’ll be replacing them more often to avoid corrosion fatigue.

Your truck will weigh more, especially if you also add custom bumpers, and you may have to adjust other truck systems to account for the weight.

So Which Is The Best Skid Plate Choice?

Despite what basic engineering properties suggest, aluminum seems to be an appropriate choice for skid plates if they are well designed; choose steel if your needs demand it but be prepared for the upkeep.

Another approach you can do is to use mostly aluminum plates with steel under the control arms or other areas of particular worry.

In either case, skid plates of any kind are always better than no skid plates at all!

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