Does Aluminum Corrode? How To Prevent Aluminum Corrosion?

Aluminum is a chemical element mostly used in high-tech machinery due to its extraordinary properties. These properties might include its lightweight, resistance against corrosion, and electrical conductivity. It is mostly used in living room windows due to its low weight and greater strength. It is also the most found element or metal on the Earth.

In this guide, we are going to learn how aluminum corrodes and what the preventions could be. The different properties and a lot of misconceptions are going to be clear after reading this guide. Let’s get started!

Does Aluminum Corrode?

Aluminum is a strong metal, and it lacks iron content, making it more corrosion-resistant. However, there is a chance that the aluminum will corrode if it is placed in certain environments for longer periods.

Why Does Aluminum Corrode?

Aluminum doesn’t corrode by itself. The chemical reactions between the metal and the environment make the corrosion possible.

However, it has the strength against corrosion if it is kept in a controlled environment as it forms an oxide layer on its surface, which helps protect the inside metal.

What Does Corroded Aluminum Look Like?

Aluminum forms a whitish-grey powder on its surface when it gets through the corrosion. However, this powder doesn’t spread evenly on the surface.

Sometimes, discoloration occurs when Aluminum is in contact with other elements like stainless steel or iron. The discoloration at the point of contact is often observed.

Does Aluminum Corrode in These Surroundings?

The surroundings are the most important factors that could cause aluminum corrosion. Let’s check them out closely and find out how lethal they could be against aluminum.

Air

• Air is very safe for aluminum as the oxide layer helps the metal protect itself from corrosion. When there is humidity in the environment, you need to be a little cautious.

Kinds of Water

• Pure Water: Pure water doesn’t harm aluminum much, so the corrosion risk is quite low. The newly formed oxide layer creates a barrier against pure water.
• Tap Water: Tap water is full of materials that can cause corrosion. There are rocky materials, salts, or impurities. However, the risk ratio is around low to moderate.
• Ice: Ice is made of water, so the type of water used to form ice is important. If it is made from pure water, you might not have lethal corrosion.
• Soft Water: Soft water is made with low concentrations of minerals, so there is a low risk of corrosion.

Underground (Soil) / Concrete

• Underground soil poses moderate to higher risks of aluminum, depending on the nature of the soil. If soil is acidic, it might pose higher risks for aluminum to corrode. So, the nature of the soil matters.
• Concrete contains a higher amount of calcium hydroxide, so there is a higher chance of corrosion. Concrete additives and Alkalinity of the material present in concrete can cause corrosion in aluminum.

Salty Environment

• Saltwater: Saltwater contains higher percentages of NaCl (Sodium Chloride) and other salty minerals, which increase the risk of aluminum corrosion.
• Seawater: Again, seawater is full of impurities and salts, so the risk percentage increases when Aluminum comes in contact with seawater.
• Salt: Salt itself doesn’t corrode aluminum. However, aluminum corrosion will start slowly if it comes into contact with moisture.
• Road Salt and Rock Salt: Road slat and rock salt increase the chances for the aluminum to get corroded as there are higher percentages of Sodium Chloride, Calcium Chloride, and Magnesium Chloride.

Acidic Environment & Alkaline Environment

• Vinegar and Acetic Acid: Vinegar contains 5-10% acetic acid, often considered mild acid. However, the longer exposure can penetrate the oxide layer and harm aluminum.
• Carbonic Acid: Carbonic acid is a weak acid and doesn’t corrode Aluminum much. However, longer exposures might create mild corrosion.
• Sulfuric Acid: It is a dangerous corrosive and strong acid. It can corrode Aluminum in no time. So, the risk factor is there.
• Alcohol or Ethanol: Alcohols that might include ethanol are not corrosive at all. There are no chemical reactions between aluminum and alcohol, so there are zero chances of corrosion.
• Hydrogen Sulfide: Hydrogen Sulfide is not corrosive itself. However, when it reacts in the presence of moisture, it can start tarnishing the metal.
• Isopropyl Alcohol: As a weak polar organic solvent, reacts with aluminum in aluminum alloy to form aluminane, which leads to corrosion of aluminum.
• Ammonia: There are low risks of corrosion when it is in a gaseous state. However, humidity can cause mild corrosion.

Do These Metals and Elements Corrode Aluminum?

• Brass: It is corrosive due to its copper properties.
• Copper: Yes, copper is corrosive to aluminum.
• Steel: Yes, galvanic corrosion occurs in the presence of moisture.
• Silicone: Silicon doesn’t have the properties to oxidize aluminum.
• Titanium: Titanium itself doesn’t corrode aluminum as both of these metals are from the same family and have similar properties.
• Zinc: Yes
• Gallium: Yes
• Chlorine: Yes, Chlorine corrodes aluminum.

Does Aluminum Corrode with Finishings?  

The different types of finishings might also help you save the metal. This finishing might include coating materials that are not easy to oxide and offer resistance against moisture and air. Powder coating and anodizing are the most common surface finishings used to prevent corrosion of aluminum.

• The powder coating is applied evenly on the surface of aluminum, which creates a barrier between the aluminum and certain factors like moisture and salts.
• Anodizing is an extremely effective finishing method that is used to preserve aluminum. In this process, the outer surface of the aluminum or any other metal is changed into a metal oxide surface. This metal oxide surface is more resistant to corrosion.

However, there is still a threat that aluminum will corrode after finishing is applied. We need to consider certain factors, including the type of finish, the moisture quantity, and the materials used for finishing.

Do Aluminum Alloys Corrode?  

Aluminum Alloys offer more resistance than pure aluminum itself. Aluminum alloy corrosion depends on certain factors, including the composition of the alloy, the protective layer, and the environment.

It has been observed that copper and zinc alloys corrode more quickly than magnesium or silicon alloys. Here are a few of the aluminum alloy families that have different corrosion resistances.

• 2xxx Series: This series consists of Aluminum-Copper alloys which make them more prone to corrosion. The availability of copper creates an imbalance and helps the corrosion process. 
• 3xxx Series: These are Aluminum-Manganese alloys. These alloys are not as strong as others but have a better resistance against corrosion than 2xxx alloys.
• 5xxx Series: This series consists of Aluminum-Magnesium alloys. The magnesium content in this alloy helps against corrosion. 5xxx alloys are well known for their excellent corrosion resistance in marine environments.
• 6xxx Series: This family consists of Aluminum, Magnesium, and Silicon and is good resistive against corrosion. 
• 7xxx Series: This series consists of Aluminum-Zinc Alloys. These alloys are not as resistive as the other alloys due to zinc content that supports corrosion.

What is the Time Aluminum Needs to Corrode?

The time period varies depending on the quality of the Aluminum or its Alloy. The environments and other conditions also tell us about the corrosion time.

Pitting corrosions are faster as compared to uniform corrosions. The protective paintings also control the time of corrosion. Anodized Aluminum prevents corrosion for years.

Aluminum Rust Vs. Aluminum Corrode

Aluminum doesn’t rust, but it corrodes. Rust is the one often observed with iron or its alloys. The rust is formed when the oxidation process of iron starts. The presence of moisture or minerals speeds up the rusting.  It is often light brown to reddish in color.

Aluminum does corrode, but this corrosion is different from rust. The oxide layer on the surface of the aluminum protects it for longer periods unless certain factors like environment, moisture, acid rain, etc., come into the equation.

How To Prevent Aluminum Corrosion?

The prevention of aluminum corrosion is vital, and multiple techniques and strategies have been used to prevent it. Let’s check them out!

Protective Coatings

• Powder Coating: Powder coating is applied to the surface of the aluminum. The powder coating is used at industrial scales to protect aluminum materials and equipment.
• Anodizing: Anodizing is a process used to protect aluminum by turning the surface of the metal into a metal oxide surface, which reduces the chances of corrosion for longer periods.
• Painting: Painting is also helpful in reducing aluminum corrosion. This paint acts as a barrier between metals and corrosive elements.
• Clear Coat: When we apply a protective clear layer on the metal, it is said to be the coated material. This process of coating is not as useful as the others but can offer a few months of safety.
• Electroplating: Electroplating is use mostly to enhance the decorative look of the material but it could help aluminum in resisting against corrosion. A layer of nickel or chrome is applied on the surface of the aluminum in this method.

Marine Grade Aluminum

We usually call 5xxx alloy marine grade aluminum, like 5052 alloy and 5083 alloy. The 5xxx alloy is made up of aluminum and magnesium. The highly resistive properties of this material help protect aluminum from saltwater. The corrosion resistance of this alloy is quite impressive and is even suited for marine environments. This is what makes it the most suitable alloy for building ships and submarines.

Corrosion Inhibitors

Corrosion inhibitors are also vital in preserving aluminum for longer periods. In this process, the protective layer is applied to the metals or the environment is changed to neutralize the oxidizing agents present in the air.

Minimize Contact with Dissimilar Elements

When you separate aluminum from dissimilar elements, there are fewer chances for aluminum to corrode. The point of contact breaks the natural oxide layer of the aluminum and it starts deteriorating. So, always save aluminum separately.

Controlled Environment

Keep the area sealed so that there are no pollutants and moisture around the metal. Keep the area or metals clean and avoid using hard materials while removing the dirt from the metals. It is better to cover aluminum with an insulating material.

Sealants

Sealants like rubber and caulk are used to protect the openings of the metals. The openings are the most vulnerable areas from where the corrosion starts. Seal those areas to protect aluminum from corrosion. This method is useful for shorter time periods.

These were a few of the methods that are being used to preserve aluminum from corrosion. There are other conventional ways like covering the metals with paper are useful as well.

Bottom Line

Aluminum is one of the most found metals in the Earth’s crust and has multiple advantages. Although it is a tough material, it is often corroded in different environments. This guide has presented the reasons for aluminum corrosion and the preventive measures that you need to keep in mind.