Aluminum is one of the most commonly used machining materials.Unlike iron and steel, aluminum does not rust on its own, as rust is a form of corrosion specific to iron-based metals. However, aluminum can still corrode under certain conditions, which can affect its structural integrity and aesthetics.In this article we focus on the phenomenon of corrosion, the types, the factors that influence corrosion, and how protective measures can extend the service life of aluminum materials.
What is Aluminum Corrosion?
Aluminum corrosion, the surface of the formation of a layer of oxide, in the form of a class of powder (white powder), patches presented.It looks like a contrast with the circumference of the material, like moldering, the essence is not moldy, but the surface oxidation phenomenon.Therefore, the essence of the spot should be the oxidation corrosion of the surface of the aluminum parts.
8 Protective Measures to Prevent Aluminum Rust
1. Surface Cleaning
It is recommended to use neutral cleaners to clean aluminum surfaces and avoid using alkaline and acidic cleaners to prevent damage to the aluminum. Excess moisture on the surface should be blown dry immediately after cleaning to prevent the cleaner from adhering to the aluminum surface for a long time.
2. Surface Finishing
Anodizing
This process transforms metal surfaces into a durable and corrosion-resistant anodized surface, especially for parts exposed to harsh weather and salt-laden environments because it won’t flake.
Sandblasting
The use of high-speed spray media (such as glass beads, ceramic particles, etc.) to clean metal surfaces, effectively removing oil, rust and other surface contaminants. It is often used in industries such as heavy machinery and shipbuilding.
Shot Peening
Shot peening and sandblasting belong to a similar process, the difference lies in the use of media, shot peening is used in the metal ball or other shapes of the shot material (such as steel balls, steel sand, etc.).
Polishing
Reducing surface roughness by physical or chemical methods to achieve a smooth effect can enhance the appearance quality and corrosion resistance of the workpiece.
3.Coating Treatment
Painting
High quality acrylic or epoxy paints with good UV resistance are recommended. A primer designed for aluminum should be used before painting to ensure better coating adhesion and durability.
Powder Coatings
Choose powder coatings that meet AAMA (American Architectural Manufacturers Association) specifications for outdoor use and are more resistant to chipping, scratching and fading than other finishes.
Electrophoretic Coating
Forms a 5-25㎛ corrosion-resistant coating on the aluminum surface through chemical reaction, effectively preventing oxidant erosion and maintaining luster for a long time.
Electroplating
Forms a metal film of 3-20㎛ on the surface of aluminum alloy, with a smooth surface and strong abrasion and corrosion resistance.
Passivation
Common passivation treatments include trivalent chromium, hexavalent chromium and chromium-free passivation, which can form a passivation film on the surface of aluminum alloys to prevent mold and oxidation.
4. Use Environmentally Friendly Water-Based Cutting Fluid
The main component of environmentally friendly water-based cutting fluid is water, containing rust inhibitor, which can effectively prevent the workpiece from rusting due to prolonged contact with water and achieve anti-corrosion effect.
5. Select Alloys with Greater Corrosion Resistance
Alloy 5052
Contains magnesium, which significantly improves corrosion resistance in wet environments and is suitable for offshore equipment such as ships.
Alloy 3003
Contains manganese as the main alloying element, which enhances strength and corrosion resistance and is suitable for industrial applications such as piping systems and fuel tanks.
6. Use and Maintenance
Avoid Galvanic Corrosion: Use non-conductive isolation techniques such as plastic or rubber gaskets between aluminum and other dissimilar metals to prevent galvanic reactions.
Regular Cleaning: Use mild detergents and warm water for daily cleaning and avoid chlorinated cleaners that may cause pitting or corrosion.
7. Packaging
VCI Packaging
Packaging technology using Vapor Corrosion Inhibitors (VCI) to prevent rust through the release of molecules in the air.
VCI Anti-Rust Paper
The Paper is an environmentally friendly packaging material that is friendly to humans and the environment. It forms a protective gas layer by adding volatilizable chemicals to the paper, which release vapors that inhibit metal oxidation. This layer of gas effectively insulates the metal from moisture in the air, thus effectively protecting it from corrosion.
Desiccant
Put an appropriate amount of silica gel or other desiccant into the package to absorb the residual moisture, and replace it regularly according to the storage conditions.
8. Spray Anti-Corrosion Oil
Application technique: Using a non-silicone based corrosion inhibiting spray oil, apply evenly in a well ventilated environment to ensure coverage of all aluminum surfaces. Use a clean air spray to help the oil penetrate into nooks and crannies.
Maintenance: Reapply anti-corrosion oil after machinery is cleaned or exposed to corrosive conditions and store aluminum parts in a temperature and humidity controlled environment to prolong their protection.
Aluminum Corrosion Resistance Chart
Aluminum corrosion resistance can be affected by external and internal factors, showing different degrees of corrosion.
Depending on the industry and the environment, different alloys are added to the aluminum composition to meet the needs of different industries.
Next, a table of corrosion resistance of commonly used aluminum alloys is listed:
| Alloy | Atmospheric Corrosion |
Saltwater Corrosion |
Chemical Industriial |
| 1100 | Excellent ★★★★ |
Good ★★★ |
Fair ★★ |
| 2024 | Poor ★ |
Poor ★ |
Poor ★ |
| 3003 | Good ★★★ |
Good ★★★ |
Good ★★★ |
| 5052 | Excellent ★★★★ |
Excellent ★★★★ |
Excellent ★★★★ |
| 6061 | Excellent ★★★★ |
Good ★★★ |
Good ★★★ |
| 7075 | Fair ★★ |
Poor ★ |
Fair ★★ |
Description:
Excellent(★★★★): Highly resistant, minimal signs of corrosion under most conditions.
Good(★★★): Resistant to corrosion, may show some signs under severe conditions.
Fair(★★): Moderately resistant, not advisable for harsh environments.
Poor(★): Low resistance, prone to rapid deterioration.
Methods of Removing Aluminum Rust
1.Chemical Descaling
Use acid detergent (such as oxalic acid, acetic acid, etc.) to chemically treat the rust on the surface of aluminum alloy to remove the surface rust and oxide layer.
2.Mechanical Rust Removal
Use sandpaper, grinding wheels, wire brushes and other tools to polish, brush and other mechanical treatments on the surface of aluminum alloys to remove surface rust and oxidation layer.
3.Spray-on Rust Preventive Oil
By spraying anti-rust oil on the surface of aluminum alloy, rust can be easily removed.
4.Metal Cleaner
Using a metal cleaner to clean the surface of aluminum alloy removes dirt and rust from the surface and can form a protective film on the surface to prevent aluminum alloy from rusting.
Summary
By understanding the principle of aluminum alloy corrosion and protective measures, can help us to correctly select the aluminum surface treatment. CNC machining aluminum parts process, choose the appropriate method to protect the aluminum surface.
Tirapid has 90% of parts made of aluminum, rich experience in aluminum machining. We are willing to share more aluminum machining tips and guidelines.
You can contact our engineers anytime(projets@tirapid.com). We will get back to you within 4 hours.
FAQs
Does Aluminum Rust?
Aluminum will not rust, but it will form an oxide layer on the surface that stops it from corroding any further.
Which Aluminum Alloys Have the Best Corrosion Resistance?
5052 and 6061 are the best aluminum alloy options. 5052 is suitable for marine environments (e.g. outdoor items). 6061 is suitable for mechanical parts, CNC custom parts.
Which Brand of Aluminum Corrosion Inhibitor is the Best?
Suggested brands: Chemworld 851AL.
What’s the difference between aluminum and iron rusting?
When aluminum is exposed to air for long periods of time, it reacts with oxygen to form a thin layer of aluminum oxide. This oxide film is very hard and tightly bound to the aluminum, effectively preventing further oxidation.
In contrast, iron rusts in an entirely different state,the iron oxide layer is loose, porous, and easily dislodged, exposing the new metal surface to continued oxidation and corrosion.The aluminum oxide layer usually remains stable and does not peel off, thus providing longer lasting protection.