It’s very common for metals to rust when it reacts with oxygen in the air. Almost every metal tastes it, and aluminum is no exception. Aluminum corrosion can affect various functional parts and reduce their lifespan.

Corrosion affects machinery, buildings, vehicles, and even electronic parts, preventing them from working normally.  As a result, the metal surface is damaged, and the metal parts have reduced durability. They may break down before they’re supposed to. As a result, the cost of maintaining your project increases significantly. Eventually, corrosion can also pose major safety risks. Because of this, it is very important for engineers and factory owners to be able to stop corrosion.

Aluminum is one of the most widely used metals on Earth. It is widely used because its weight is significantly lower than that of other metals. Considering the strength-to-weight ratio, aluminum is stronger than many metals. Its use can be seen in automobiles, buildings, marine, and industrial applications.

A lot of people don’t think that aluminum corrosion is important. They think aluminum is naturally corrosion-protected. Well, aluminum corrosion may still happen in certain situations. High indoor humidity, outdoor rain, and saltwater may affect it.

Aluminum corrosion may create pits and discoloration on your parts. Eventually, it becomes the root cause of part failure. Because of this, it is important to know what aluminum corrosion is and how it happens. And this article can help you all the way.

Understanding Corrosion on Metal

Corrosion is the chemical breakdown of a metal when it is exposed to environmental conditions. Typically, when metal comes into contact with oxygen and moisture, it forms an oxide. The surface reacts with moisture in the presence of oxygen. This process is known as rust formation, and the electrochemical reaction is called a redox reaction. This entire process occurs due to the chemical instability of metals.

One of the most famous types of corrosion is rust. It specifically refers to iron and its alloys. When iron reacts with oxygen and water, it forms iron oxide. In terms of iron, it lacks the protective layer that aluminum has, so its rusty surface becomes crumbly and porous. It acts like a sponge, trapping more moisture against the metal. It lets rust eat away at the structure until the metal completely breaks down.

Some other metals corrode in different ways depending on the surroundings. Copper develops a green patina, which actually protects the underlying metal. On the other hand, gold and platinum are noble metals that rarely corrode. However, many factors, such as salt, acid rain, and chemical waste, may affect industrial metals.

Preventing corrosion is the main challenge for engineers and homeowners alike. Here, many people prefer various types of coatings to stop them. Some special coatings, such as paint, oil, or plastic, are used to create a barrier between the metal and the air. Galvanizing is also a remarkable method for protecting steel. Well, by understanding the chemistry, we can create metals that can last for decades without breaking.

Is Aluminum Corrosion-Resistant? How Easily Does Aluminum Corrode?

Aluminum is naturally corrosion-resistant. Once aluminum is exposed to the air, it quickly forms a thin oxide layer. This protective layer covers the metal surface and blocks further corrosion. As a result, aluminum corrosion happens much more slowly than other materials. However, certain environments may push it forward.

Normal Indoor

In a normal indoor environment, aluminum is highly stable. The air and moisture levels in homes and offices are very low. Consequently, they remain drier than outside. As there is very little moisture, the oxide layer remains intact and strong. This kind of invisible shield prevents any significant damage. You may notice that aluminum materials stay shiny for decades without damage.

However, in an indoor environment, aluminum may still corrode. First, if the indoor humidity is high, condensation on części aluminiowe may accelerate corrosion. Second, indoor air may contain chemicals that attack aluminum. Third, dust and other contaminants may also hold moisture and corrosive chemicals that may accelerate the corrosion. Besides, a sudden temperature rise may also cause aluminum to corrode.

Outdoor Environment

In outdoor settings, several factors may affect aluminum corrosion. It faces more challenges outdoors than indoors. Metals are constantly exposed to rain, humidity, and temperature fluctuations. When the metal wets, it reacts with oxygen in the rainwater to form an aluminum oxide layer. This way, it thickens the protective oxide layer over time. Sometimes, dust and dirt may be trapped on the surface, making it look dull.

Gradually, the metal loses strength and may no longer deliver the same output as before. Although it does not rust like iron. The grayish layer that forms is a sign that the metal is protecting itself. Many outdoor items, such as ladders and poles, can last for 30 or more years.

Marine or Saltwater Situations

Saltwater is the most corrosive environment for aluminum. Salt contains chloride, which is heavily aggressive toward the oxide layer. When it comes into contact with the surface, it begins to eat through the protective layer, creating small holes. Often, it looks like tiny bumps or while holes known as spitting corrosion.

In the marine sector, they use special marine-grade aluminum alloys for safety. These alloys are mixed with magnesium to remain strong and resist sea salt. Despite these alloys, the owner must generally rinse the metal with water. Without proper care, metal might weaken over time. This is why you need to keep an eye on boats and docks at all times to keep them safe and working.

Industrial or Acidic Environment

Industrial areas often have other gases such as sulfur and nitrogen. These gases are a threat to aluminum when mixed with rainwater. It causes mild acidic rain on outdoor aluminum surfaces. These acids can easily damage and dissolve the protective oxide layer before it regrows. Once the shield is gone, the underlying metal becomes quite vulnerable and can degrade. It results in a dark, pitted, and rough surface.

In these conditions, aluminum needs extra care to protect itself. Engineers often use a thick coating or paint to avoid these problems. Anodizing could also be a reliable solution, as it creates a much thicker shield. Without extra steps, these toxic fumes would eventually weaken the strong metal.

Types of Aluminum Corrosion

Aluminum works great in many environments, it’s true. However, it can still suffer from different forms of corrosion. These problems appear under specific conditions such as moisture, chemical exposure or mechanical stress. You must understand the common types of aluminum corrosion. This way, you can identify early risks and choose the right prevention methods.

Atmospheric Corrosion

Atmospheric corrosion is the most common form of environmental corrosion. When the metal comes into contact with air and moisture, it reacts immediately. Thus, it creates a thin, protective grey film.

Possible Prevention Methods: The initial step to prevent this kind of corrosion is to keep the metal dry by preventing moisture buildup. Apply wax or paint coating to create a direct barrier. You may also use anodized aluminum here. This technique adds a thicker, tougher exterior protection layer.

Korozja wżerowa

Pitting creates tiny holes in the aluminum surface. Generally, it is triggered by chloride ions found in seawater or chemicals. These tiny holes grow deeper over time, concealing damage beneath a clean-looking surface.

Possible Prevention Methods: To get rid of this pitting, you have to rinse the metal frequently with fresh water to remove salt. Recommend using high-quality protection, such as an epoxy coating. Choose magnesium-based alloys, as they can resist small chemical attacks.

Galvanic Corrosion

Galvanic corrosion occurs when aluminum meets other metals, such as copper and steel, when wet. Aluminum acts as a battery, causing a chemical reaction between two metals. It is a very fast and destructive process.

Possible Prevention Methods: To prevent galvanic corrosion, avoid direct contact between aluminum and dissimilar metals. You can use rubber spacers or plastic to separate metals from touching. Apply waterproof sealants to the joints. Always try to use similar metals to avoid chemical reactions.

Crevice Corrosion

Crevice corrosion forms in narrow, tight gaps. It is because when these gaps trap water and chemicals. Small spaces under bolts, washers, or overlapping plates are high-risk areas. Lack of oxygen in the gaps leads to rapid decay there.

Possible Prevention Methods: Seal all gaps in metal with waterproof silicone or caulk. If possible, use solid welding rather than rivets or bolts for metals. Design the structure efficiently to avoid getting trapped in water. Set non-absorbent gaskets between the two surfaces. Inspect regularly moisture trapping before severe damage occurs.

Intergranular Corrosion

This type of corrosion attacks the microscopic boundaries between the metal grains. It is hard to see on the surface, but it weakens the metal from the inside. Generally, improper heat treatments lead to this situation.

Possible Prevention Methods: In this case, use particular grade alloys that contain low carbon content and an additional stabilizer. Ensure your metal undergoes proper heat treatment during manufacturing. Avoid overheating when welding or fabricating. Always work with a reputable supplier who follows strict quality standards.

Filiform Corrosion

Filiform corrosion appears as a thin, branching thread on a painted surface. It starts at the point where the paint is peeled off the aluminum surface. The reason behind this could be a scratch or humid conditions under the painting. It ruins the product’s appearance.

Possible Prevention Methods: Before starting the painting, always use a high-quality primer. Keep the metal clean and dry and maintain a humidity level below 70%. If there are any cracks, repair them before painting. The surface should be chemically cleaned, and a corrosion-resistant coating applied to the aluminum.

Exfoliation Corrosion

Exfoliation corrosion is a severe form of aluminum corrosion that lifts the metal layer. It typically looks like peeling or flaking apart. Aerospace industries are at the most risk as they use these high-strength alloys. It significantly decreases the metal strength.

Possible Prevention Methods: Select alloys specially designed to reduce exfoliation corrosion. You can also apply surface treatment for further protection, such as anodizing. Apply thick, specialized coatings to the edge of the metal sheet. Inspect high-stress aluminum regularly for cracks. Avoid alloys with layered grain textures in challenging situations.

Deposition Corrosion

This type of aluminum corrosion occurs when ions from other metals deposit on the aluminum surface. This particle later reacts with the surface in the presence of moisture. This way, it creates galvanic cells and accelerates corrosion beneath the deposit.

Possible Prevention Methods: Keep the aluminum surface clean and free of debris. Avoid using copper pipes in upstream plumbing relative to aluminum. Besides, do not grind dissimilar metals near aluminum. Rinse the metal daily to remove dirt. You may also use special coatings to reduce surface exposure.

Pękanie korozyjne naprężeniowe

Stress corrosion is the combination of mechanical stress and corrosive environment. The cracking under high stress and in certain circumstances. It’s an invisible damage that might not show during work. Suddenly, it will fail without warning.

Possible Prevention Methods: To prevent cracking, reduce the tension or extreme load on the metal. In building times, use stress-relief heat treatment for metals. An efficient design and special alloys would be a good option to resolve such problems. Moreover, keep these metals away from chemicals that trigger cracking.

Erosion Corrosion

Erosion-corrosion is caused by liquids or gases that wear down the protective oxide layer. Constant scrubbing of the metal might prevent the shield from regrowing. Removing the layer reveals raw materials that can be constantly attacked.

Possible Prevention Methods: Design pipes with smooth curves instead of sharp turns. Maintain a stable fluid velocity for safe flow through the system. Employ hard, sturdy aluminum alloys that can resist surface wear. Apply anodized aluminum coatings to high-flow areas to resist physical wear and tear.

Microbiological Induced Corrosion

Microbiological corrosion refers to the growth of bacteria and fungi on aluminum metal. These elements usually grow on the wet areas of aluminum. Such organisms produce acids and waste products. These byproducts directly attack the aluminum surface. This type of aluminum corrosion may not get proper attention, but it can cause serious damage.

Possible Prevention Methods: Clean the metal surface of water and prevent it from pooling on or around the aluminum. Regular cleaning is necessary to remove any slime or biological growth. You may use antimicrobial coatings in high-risk environments. Make sure there is a good drainage and ventilation system to prevent the growth of microorganisms.

Will Aluminum Rust if It Gets Wet?

Technically, aluminum does not rust. This term is only used for iron and steel. Steel and iron react with water and oxygen when they are wet. It creates a flaky powder that gradually eats away at the metal. On the contrary, aluminum’s rust resistance reacts differently when it is wet. It forms a layer of aluminum oxide on the surface, which later protects it from harsh conditions.

Even if you submerge the metal in water, it can stay strong for a long time. Unlike iron and steel, it does not flake off and is waterproof. However, if the water is salty or acidic, it begins to wear down. Thus, you might see small, dull, grey spots on the surface.

Aluminum vs. Stainless Steel: Which is More Corrosion-Resistant?

Compared to aluminum, stainless steel is more corrosion-resistant. This steel type contains chromium, which forms a highly durable, invisible film. This film is far more durable than the aluminum oxide layer. In harsh conditions, such as a salty or acidic environment, it is less likely to wear and can hold its ground better.

Anyways, aluminum is much cheaper and lighter than stainless steel. While stainless steel is strong and corrosion-resistant, it is difficult to shape. Generally, it costs more than aluminum. Also, the modern world requires a flexible, lightweight solution for modern technologies. Aluminum is preferred for cars and airplanes, where weight matters a lot. So, if you want a great balance between cost, weight, and protection, aluminum is the winner.

Five Effective Ways to Prevent Aluminum Corrosion

You can control aluminum corrosion in several ways. But choosing the right method may depend on the specific type of aluminum corrosion. With these methods, you can extend the life of aluminum parts.

Anodowanie

Anodizing is an electrochemical process that thickens the oxide layer. It makes the surface stronger and more durable, helping it overcome complexities. Also, it provides great protection against wear. For a better look, you can dye these metals in multiple colors.

Protective Finish

There are many ways to ensure a protective finish for your metals. You can apply powder coating, paint, and clear waxes to the surface. These finishes create a physical barrier between the air and the surface. As a result, it prevents moisture and chemicals from touching them.

Keeping the Aluminum Parts Clean and Dry

Continuously cleaning and keeping materials dry are crucial to preventing corrosion. Moisture and dirt are the main causes of corrosion. Regular cleaning keeps your metals free of salts, water, and chemicals that can trap water. It is the easiest way to resolve long-term damage.

Corrosion Inhibitors

These are vital chemical additives applied to the surface or nearby liquids. They react with metals to form a thin, protective film on the surface. This film prevents chemical reactions that cause decay and is suitable for a closed cooling system.

Cathodic Protection

Using a sacrificial metal such as zinc or magnesium reduces corrosion. In an electrochemical cell, aluminum is used as the cathode and sacrificial metal as the anode. Here, the active metal corrodes first, saving the aluminum from damage. This common technique is used on boats, ships, pipelines, or underwater structures.

How to Remove Aluminum Corrosion or Oxidation

If your aluminum parts already have rust, then how can you clean them before applying the proper preventive measures? Even here, there are multiple ways you can clean your aluminum parts. Each method has its unique advantages and limitations. Based on your preference, you can choose the right method for your project.

Laser Rust Removal

Laser rust removal uses a high-powered beam of light to evaporate corrosion. When the energetic light hits it, rust breaks into tiny particles. While removal, it does not damage or decrease the strength of the underlying metal. The process is a very precise, fast, and clean way to remove corrosion.

Plusy

• Completely contactless process, no need for physical scrubbing during work.
• Zero consumables requirement, eco-friendly process.
• High precision allows it to clean tight spaces or corners easily.

Wady

• Requires a high initial investment, as the machine is expensive to buy.
• High risk to the eyes if they are not protected during work.
• It takes a little bit of time for thick layers.

Abrasive Blasting

Abrasive blasting uses high-pressure air to shoot abrasive material. These shoot small particles, such as glass, and the scrub removes coating and corrosion very quickly. It is a powerful solution for industrial items with large surfaces. It removes aluminum corrosion, leaving a glossy, uniform finish.

Plusy

• This method is used to clean every large surface area rapidly.
• Compared to other methods, it removes thick, heavy corrosion easily.
• It can also prepare the surface for post-processing, like painting.

Wady

• There is a high chance of warping thin aluminum sheets.
• Produces a lot of dust during operation.
• Requires heavy protective gear and special equipment.

Chemical Cleaning

Chemical cleaning uses different chemical solutions to remove oxide layers. Acids and alkalines are the most commonly used. These chemicals remove oxidation and other impurities from the aluminum surface. You may also dip the part in a tank or spray the liquid on it. Thus, it works by breaking the bond between metal and corrosion.

Plusy

• Chemicals easily reach hidden cracks and complex geometries.
• Ideal solution for mass production.
• Removes aluminum corrosion without mechanical abrasion.

Wady

• Harsh chemicals can severely damage surfaces if misused.
• Requires careful handling and waste disposal.
• Also, it can damage metal if left too long.

Fine Grit Sandpaper

Fine-grit sandpaper is a simple, affordable way to remove aluminum corrosion. It’s a manual process to rub away surface contamination. You move the paper in small circles to lift the dull oxide layer. This is why it is an ideal option for small spots or home DIY projects.

Plusy

• Allows high-level control over the finishing.
• Budget-friendly, low-cost, and widely available.
• Perfect for small, delicate part repairs.

Wady

• Time-consuming for large area surface works.
• Physical effort is required for rigorous cleaning.
• Hard-to-reach tight spaces or corners.
• It can lead to surface damage from continuous hard scrubbing.

Często zadawane pytania

Does WD-40 Stop Aluminum Corrosion?

Yes, WD-40 works better and helps protect aluminum from corrosion. It works as a water displacer and a light lubricant, creating a thin oily film that protects from moisture and air. But the thing is, you have to reapply it daily, because it evaporates or washes away.

What is the Best Corrosion Inhibitor for Aluminum?

The best inhibitor usually depends on the purpose. For heavy-industrial aluminum, chromate or cerium-based coatings are strong and useful. For the home, specialized clear waxes or lanolin spray work better. They provide a much longer shield for metals.

How Long will Aluminum Last Outside?

Aluminum is much more durable and can easily last for 30 to 50 years. In dry weather, it may last even longer without any structural damage. The underneath metal stays strong, even though the surface looks dull and grey.

Will Aluminum Rust in Winter?

Aluminum will not rust in winter because it does not contain iron. However, salt and melting snow might be the cause of spalling corrosion. But the weather, coldness itself, cannot damage the metal.

Podsumowanie

Aluminum is naturally a corrosion-resistant metal. It is strong and very lightweight compared to other metals. When exposed to air, it forms a very thin aluminum oxide layer. It typically prevents further oxidation and the formation of rust on the surface. This layer typically keeps the metal safe and slows the rusting of aluminum. However, corrosion may still happen in some situations.

Indoors, excess humidity may drive this corrosion. On the other hand, in the outdoors, rainwater may create aluminum corrosion. Besides, saltwater or other marine situations may also be responsible for aluminum corrosion.

There are many ways to stop this trouble from happening. You can take preventative steps based on the type of rust. Also, you can use these methods to ensure the metal parts will remain stable for a long time after you make them.

You can also use more than one method to remove rust. Metal parts can be cleaned using lasers, sandblasting, chemicals, or mechanical tools. But picking the right way might depend.

Laser cleaning is fast and efficient. But this technology is quite expensive. On the other hand, chemical, sandblasting, and mechanical cleaning are cheaper. However, these methods are messier. Chemical cleaning is not environmentally friendly.

Moreover, mechanical cleaning may damage delicate parts. Sandblasting may not be ideal for small parts. Chemical cleaning needs a proper place of operation.

Aludie Casting is a business that performs skilled odlew aluminiowy. The foundry makes a wide range of parts, from car parts to medical parts to industrial parts. Please get in touch with us if you need more information or have ideas.