Why does aluminum do not rust?

When using our materials, it is therefore useful to take precautions to prevent or minimize corrosion.

Table of Contents Show

Table of Contents
Wat is a corrosion?
Contact corrosion
The most important tips to avoid aluminum corrosion:
Opportunities for improvement:
other topics …….
Heat treatment without usage of natural gas
Frustration when producing threads
Heat treatment of aluminum
What is rust?
Does aluminum rust?
Aluminum oxides in nature
How to protect aluminum from corrosion
Does aluminum rust easily?
Why does iron rust but not aluminum?
Is aluminum less likely to rust?
How is aluminum corrosion resistant?

What is a corrosion?
Contact corrosion
The most important tips to avoid corrosion
Opportunities for improvement

Wat is a corrosion?

Like any metal, aluminum forms a natural oxide layer when it comes into contact with oxygen. In contrast to steel, the corrosive layer comes to a halt after approximately 2.5-4 nm, thus protecting the underlying metal from corrosive destruction. This layer remains stable in the pH range of 4.5 to 8.5, which means that it is not attacked by corrosive gaseous or liquid media. In this state, aluminum has clear advantages over steel.

Contact corrosion

During construction and in various applications with untreated aluminum semi-finished products, care must be taken to avoid contact corrosion. At contact points with more noble metals such as iron and copper, a contact element can form after the ingress of moisture, i.e. a low electrical voltage, under the chemical effect of which the aluminum is attacked.

The most important tips to avoid aluminum corrosion:

do not bring into contact with materials having an electrochemical voltage potential of > 50 mV
avoid contact with media outside the pH range of 4.5 to 8.5
seal crevices ≤0. 5 mm (connected to component)
do not allow moist parts to come into contact with steel, copper, brass or bronze
avoid direct contact of parts when stacked vertically
always use interlayers that are completely dry and free of acid residues
do not store parts directly on wet or contaminated wood (e.g. pallets)
never use rags that have been previously used to clean/dry steel, brass, copper, etc. or that are dirty
never use abrasives (pads paper, etc.) with which other metals have been previously processed
process only a single material on the machine. If you do change, however, then change the emulsion beforehand.
even the most elaborate filtration systems cannot separate finest foreign metal particles
immediately remove machined components and clean and dry them thoroughly
use only cooling emulsions with a pH range between 4.5 to 8.5
perform weekly check of pH value of the emulsion
do not use cleaners with a pH value >8.5
do not store aluminum in areas with changing climatic conditions

Opportunities for improvement:

Aluminum products can be specifically protected against corrosion by strengthening the oxide layer through anodizing or surface treatments such as painting. During anodizing, the sealing oxide layer is created artificially. It protects the aluminum from reacting with water and seals it airtight.

In addition, the aluminum can be protected from corrosion by changing the alloy. Just a few percent magnesium make it seawater-resistant and therefore suitable for shipbuilding.

With G.AL® C250 Elox Plus, GLEICH Aluminum has a product made from the alloy EN AW 5083, which has been optimized for optical requirements after anodizing (anodizing).

Product description G.AL® C250 ELOX PLUS

Heat treatment without usage of natural gas

How a German aluminium plate producer is on a worldwide solo attempt and sets new quality standards.

Frustration when producing threads

It doesn’t have to!

By using a process that is aligned to the specific material, durable external and internal threads can be produced in a flash.

Heat treatment of aluminum

GLEICH Aluminium is one of the few manufacturers of aluminum cast plates with an in-house heat treatment facility.

Does aluminum rust? It’s a question we get asked all the time, and the short answer is no, but that doesn’t mean it’s invincible.

Today we’re exploring the differences between rust and aluminum corrosion. We’re going to answer the question, “does aluminum rust” by looking at the differences between rust and aluminum corrosion, examining the different types of corrosion, and finishing with tips to protect your aluminum from degradation.

What is rust?

The term “rust” refers to that reddish-brown flaky stuff that appears on some metal surfaces that are not well protected and are exposed to the elements.

Rust is a chemical reaction of iron and oxygen when exposed to water and moisture in the air. So, if rust happens when you expose a piece of metal to air and moisture over time, does aluminum rust?

Both rubies and sapphires are corundum aluminum oxides: additional trace elements give them color.

Does aluminum rust?

“Rust” results from the oxidization of iron. Aluminum, technically, cannot rust! But aluminum does oxidize, in a chemical process like the creation of iron oxides. This significantly affects its physical and chemical properties.

Aluminum oxides in nature

Aluminum as a refined metal does not occur in nature. Instead, it is found in aluminum bearing minerals, and most often refined from the rock “bauxite.” Some precious gems, such as rubies and sapphires, are made of an aluminum oxide and colored with trace amounts of other elements.

Aluminum oxides help protect the metal from further corrosion. Unlike rust, aluminum corrosion won’t flake or clean off easily. And, instead of the reddish-brown color typical of rust corrosion, aluminum corrosion appears more powdery-grey, similar to the natural color of aluminum, making it difficult to see.

Here are the different types of aluminum corrosion:

Atmospheric: This is when aluminum corrodes due to exposure to natural elements and is the most common type of corrosion found in this metal. This corrosion is dependent on the amount of moisture in the air, so that’s why aluminum corrosion occurs at different rates around the world. Other atmospheric conditions that contribute to aluminum corrosion include wind speed and direction, temperature, precipitation, pollutants in the air, and proximity to natural water sources (especially saltwater).

Galvanic: This occurs when aluminum is physically connected to a noble metal (ruthenium, rhodium, palladium, osmium, iridium, platinum, gold, or silver) via an electrolyte. The intensity of corrosion is highest at the intersecting points and gradually decreases further away you get from this point. It corrodes faster than atmospheric corrosion.

In most cases aluminum pitting is cosmetic unless the aluminum suffers deep stress over a long time.

Pitting: When small holes (pits) develop in an aluminum surface, it's known as pitting corrosion. These pits are common areas where salt (alkaline or acidic) settled and corroded the surface of the metal. These generally don’t cause any structural or strength damage to the metal but can affect its aesthetic.

Intergranular: This type of degradation occurs between the grain boundary and the alloy microstructure when they are electrochemically different. The exchange of microns between these areas causes pitting corrosion and the corrosion spreads rapidly along grain boundaries.

Exfoliation: This corrosion occurs in aluminum with marked directional structures, which is common when the metal has gone through hot or cold rolling processes. The way the corrosion spreads, makes the surface of the aluminum appear to lift (hence the name “exfoliation”). It can cause severe deformation and weakening of the metal. You may also notice pitting, flaking, and blistering on the surface.

General: Corrosion that affects the entire surface evenly is often caused by exposure to highly acidic or alkaline substances. In high and low pH solutions this type of corrosion will not protect the metal underneath. Eventually, it will completely degrade the aluminum.

Deposition: When dissimilar metal is deposited on the aluminum, you get localized corrosion. When the ions on the dissimilar metal are lower than the aluminum, it causes pitting in the aluminum.

Stress corrosion cracking (SCC): This is when an aluminum fails and cracks. For corrosion to happen in the stress cracks, three conditions must exist:

it needs to be a high-yield alloy,
the environment must be humid or wet, and
there must be tensile strength in the material to open the crack.

Erosion: This corrosion is caused by a high-speed water jet on the aluminum. This happens with the right combination of velocity and pH levels in the water. With pure water, corrosion happens slowly, but in water over a pH of 9, the degradation rate increases.

Corrosion fatigue: Metals exposed to prolonged stress can crack. Salty water or moisture needs to be present for the corrosion to occur in the newly formed stress cracks.

Filiform (or wormtrack): This is when corrosion starts as pitting then "worms” across the surface of the metal. The degradation is expedited when exposed to chloride anions or high humidity.

Microbiological induced: This is corrosion caused by microorganisms or fungi. It’s common in fuel and lubrication oil tanks. The organisms consume the oils and excrete an acidic compound that causes corrosion on the aluminum.

Aluminum corrosion can be fully prevented with application of a sealant.

How to protect aluminum from corrosion

So if you think about the answer to the question “does aluminum rust?” the answer is no, but it does corrode if not taken care of. Corroded aluminum weakens the metal over time.

In a mild climate aluminum corrodes very slowly. Atmospheric factors like rain, humidity, acidity, and other chemical stressors make aluminum corrosion more likely. Cleaning and drying can help aluminum that is in regular contact with stressful climates.

As with other metals, a surface finish can help protect aluminum. Clear coats of protectant are available to preserve aluminum’s natural look. Paint, powder coat, or an innovative finish like IronArmor can provide both color options and additional protection.

So now you know the answer to does aluminum rust. Curious and want to learn about aluminum? Read more about the uses and popularity of aluminum coatings and castings.

Does aluminum rust easily?

Rust is a type of corrosion (the wearing-away of metal), and to put it simply, aluminium does not rust, but it does corrode. Although these terms are often used interchangeably, they are fundamentally different. As with any metal, when it comes into contact with oxygen, an oxide layer will form on aluminium.

Why does iron rust but not aluminum?

Unlike iron and steel, aluminium does not rust or corrode in moist conditions. Its surface is protected by a natural layer of aluminium oxide. This prevents the metal below from coming into contact with air and oxygen.

Is aluminum less likely to rust?

Aluminum alloys contain almost no iron, and without iron, the metal will not rust, but it will oxidize. When the alloy is exposed to water, aluminum oxide film forms quickly on the surface. The hard oxide layer is resistant to further corrosion and protects the underlying metal.

How is aluminum corrosion resistant?

Aluminium has excellent corrosion resistance because it spontaneously forms a thin but effective oxide layer that prevents further oxidation. And aluminium oxide is impermeable. However, aluminium alloys perform differently in saltwater environments or in a saline atmosphere.