Steel Driveway Gates: Steel vs Aluminum

Steel Driveway Gates vs. Aluminum Driveway Gates

Dual swing aluminum driveway gates.
Aluminum Driveway Gates In Metal Gate Manufacturing Workshop

 


“Steel Rusts, But Aluminum Doesn’t Rust…Right?!?”


Read On To Find Out

The (Surprising) Similarities & Differences Between The Two!


Part I:

What Are Steel & Aluminum?

Steel and aluminum are the two main different types of metals from which metal driveway gates are created.

Wikipedia: Steel

 

Steel is an alloy of iron with typically a few tenths of a percent of carbon to improve its strength and fracture resistance compared to iron. Many other elements may be present or added. Stainless steels that are corrosion– and oxidation-resistant need typically an additional 11% chromium. Because of its high tensile strength and low cost, steel is used in buildingsinfrastructuretoolsshipstrainscarsmachineselectrical appliances, and weapons. Iron is the base metal of steel. Depending on the temperature, it can take two crystalline forms (allotropic forms): body-centred cubic and face-centred cubic. The interaction of the allotropes of iron with the alloying elements, primarily carbon, gives steel and cast iron their range of unique properties.

Square tubing steel 3x2 on floor
Steel tubing and sheet metal for driveway gate with blue-gray colored “mill scale” on the raw surface. These oxides must be removed for proper powder coat adhesion.

 

Welding steel gate frame.
Welding the frame for a steel driveway gate.

 

Atlanta driveway gate design by JDR Metal Art.
Steel driveway gates after metal fabrication and powder coating is complete and the installation in Atlanta is finished.

Steel is probably the more commonly used of the two metals for driveway gates. And it’s nearly always used in the construction of bridges, automobiles and skyscrapers; steel is perhaps the most integral commodity of the modern era. Widely known for it’s strength and endurance. Cost effective and very strong but 3x heavier than aluminum and more prone to corrosion and oxidation, also known as “rust”. Raw steel has a dull white appearance when fully cleaned.

Driveway gate being sandblasted free of rust and mill scale.
Steel driveway gate being sandblasted down to clean white metal for proper powder coat adhesion.

Wikipedia: Aluminum

Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It has a great affinity towards oxygen, and forms a protective layer of oxide on the surface when exposed to air. Aluminium visually resembles silver, both in its color and in its great ability to reflect light. It is soft, non-magnetic and ductile. It has one stable isotope, 27Al; this isotope is very common, making aluminium the twelfth most common element in the Universe.

Aluminum, just like steel, is prone to corrosion. Although it is substantially more costly than steel, it weighs only 1/3 as much and has a very high strength-to-weight ratio which makes less work for both the gate installer and the automatic gate openers.

Aluminum sheet for custom farm gate in Ocala, Florida.

Aluminum is a shiny white metal most commonly used for building aircraft, boats and medical devices. It is softer than steel and requires much greater attention to cleanliness in order to weld properly.

Horse farm driveway gate with plasma cut horse and fence design.
Polished aluminum driveway gate on steel welding table.

With a melting point of only 1100 degrees F vs. 2000+ degrees F for steel, aluminum is much more reactive to heat and likes to “move” i.e. warp if it is not obsessively clamped during fabrication.

Aluminum driveway gates finials.
Aluminum driveway gate on steel welding table, with cast aluminum fleur de lis finials.

 Aluminum’s outstanding corrosion properties are highly desirable for customers living in salty environments such as near the ocean or close to a road that will see lots of salt through the winter.


Part 3:

Aluminum vs. Steel

 

Aluminum tubing vs steel tubing for building custom driveway gates.
Aluminum gate frame tubing on the left; steel tubing is on the right.

The Problem:

Corrosion, Oxidation, Rust & White Rust

rusty gate hinges
Rusty orange gate post and hinge frame. Hinge has a galvanized coating and has not rusted after several years.

We’ve already learned that steel and aluminum are two different types of metals. All metals suffer from varying degrees of corrosion when exposed to oxygen. Both steel and aluminum are susceptible to corrosion in the form of oxidation. A clean metal surface requires immediate protection from oxygen in the atmosphere or else an ever expanding layer of oxidation will form on the surface. When oxidation i.e. corrosion occurs on steel it is called “rust“. Due to its stained orange or brown color, rust stands out on steel like a sore thumb. When oxidation is formed on aluminum, it’s simply called corrosion, or sometimes “white rust”.

Simply put; oxidation is corrosion and in most cases it’s undesirable. It is sinister because it forms beneath the painted surface until it spreads and begins to push the paint off the surface in many areas at once.

Steel

One solution some clients choose is to entirely forego the powder coat and wish to let the metal age naturally into a brown finish.

Steel Before Outdoors Exposure:

Steel driveway gate before rust.

vs.

Steel After Outdoors Exposure (left to rust naturally):

Rusted raw steel driveway gates for Sacramento California property entrance.
Customer in Sacramento chose to let his gate rust naturally.

Aluminum


Myth: Aluminum Doesn’t Corrode & Is Superior To Steel

Fact: Aluminum & Steel Both Corrode When Exposed to Mother Nature


Paints EASILY Peel & Blister Off Corroded Aluminum

In aluminum the layers of oxide which form are called “white rust“. Unlike steel, aluminum corrosion is white and powdery once it gets thick, therefore it can be very hard to notice at first. Then, suddenly it is noticed everywhere at once.

Paint peeling off of an aluminum estate gate.
Paint flaking off aluminum estate gate due to the visible powdery white residue which is sometimes referred to as “aluminum rust”.

On aluminum, an invisible, very thin film forms immediately and grows exponentially until a visible white film appears, typically within a few months.

Paint peeling off aluminum.
Peeling paint failure on shiny aluminum due to lack of adhesion. Paint of powder coat adhesion matters for both steel and aluminum, but aluminum is truly the more finicky of the two metals.

Installed gates are more or less prone to corrosion depending on the climate and microclimate of the gate installation site. A metal gate at an oceanside villa or very close to a heavily salted winter highway would be much more prone to corrosion than would the same metal gate in a relatively salt-free environment.

The Answer:

Building Corrosion Resistance with Powder Coating

louisiana plasma cut gates by jdr metal art 2015 spraying zinc rich primer powder coat
Spraying Zinc Rich Primer on a steel driveway gate for the ultimate in steel corrosion resistance.

The first three stages before painting or powder coating any metal such as steel or aluminum are “prep, prep, prep”. The more time spent preparing the surface, the longer the paint job will last. Nearly all coating failures can be attributed to a failure in surface preparation.

Although in the past steel and aluminum each required their own separate preparation approaches to get the best corrosion resistance results over the long term, some newer technologies demonstrate impressive corrosion resistance results on both steel and aluminum, thus streamlining the finishing process and getting gates shipped out sooner with a longer lasting finish than ever before.

Once the preparation is complete it’s time to protect the fresh metal surface. It is covered with a metal coating, typically either paint or powder coat. Preferably powder coat. Once the gate is coated and exposed to the elements at its installation site then nature begins her testing of the work of the painter or powder coater until sooner or later the coating fails.

Cost

Paint is generally the lowest cost, lowest technology coating method. Powder coat is a high capital investment, high technology process and costs more initially, although it is an investment that pays off over time in maintenance-free nature of quality powder coats.

Cure Times

Paints cure by a chemical reaction and most, if not all, suffer from extended cure times, especially for water based paint products. Other paints such as acrylics and enamels cure faster than water based paints but use harmful chemicals such as accelerators and hardeners while still falling short of the hardness of powder coat.

Powder coat is an environmentally friendly method of painting with an electrostatic applicator which uses no water or chemicals but rather a large parts oven to cure the paint after it has been applied. The part is baked at 400 degrees for 10 minutes and is completely cured once it cools down to room temperature.

Once the gate has been powder coated it is visually impossible to distinguish whether it is made from aluminum or steel. The difference would not be known until the time for handling and installation of the gates due to the weight difference between steel and aluminum.

Aluminum & Steel Driveway Gate Designs

Although steel is several times stronger than aluminum, steel also weighs several times more than aluminum. A heavier gate means there will be added stress on the gate opener system.

A common misconception is that aluminum does not rust. Technically this statement is true because “rust” refers specifically to iron oxide which is created when iron (the main ingredient of steel) is exposed to moisture. While steel corrosion is called “rust” aluminum corrosion is called aluminum oxide or “white rust“.

Steel and aluminum will both corrode although at different rates. Given the same environment aluminum will corrode at a slower rate than steel.

For our aluminum gate designs use marine grade aluminum materials because they contain magnesium which makes our gates much more resistant to moisture’s corrosive effects than a purer aluminum would.

Proper Powder Coating Adds Long Life to Both Aluminum & Steel!

Despite the differences in corrosion resistance between steel and aluminum; advanced powder coating technology allows us to greatly reduce the likelihood of corrosion on either our steel or aluminum gates.

Powder Coated Aluminum:
Aluminum metal driveway gates with copper finish.
Aluminum driveway gates with copper powder coat finish.

We use powder coatings which provide the perfect barrier between metal and moisture. Our steel gates all receive a zinc-rich epoxy primer specifically formulated for exterior applications. The primer prevents the spread of rust by creating an impermeable layer of zinc-infused epoxy directly over the steel surface. The top coat (usually black) goes on last and looks nice but the primer is what does the work keeping the steel gate rust-free for a long time.

Powder Coated Steel:
Ornamental driveway gate powder coating
Steel driveway gate with copper powder coat finish.
Bronze powder coat on steel driveway gate.
Steel driveway gate with aged copper finish.

Ranch driveway gates for Florida Aluminum entrance gates with black powder coat finish.

Steel & Aluminum Driveway Gates

JDR Metal Art specializes in handcrafting exquisite entry gates for clients from all walks of life. No matter what your needs, we have the perfect solution and enjoy taking on new challenges all the time.

Here is a selection of some of our steel driveway gates.

You can check out some of our aluminum driveway gates here.

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