Aluminum is widely used in the manufacturing, cookware, construction, and transport industries. This is because it is naturally lightweight and corrosion-resistant. However, in certain applications, it requires an extra layer of protection. There are various aluminum finishing techniques used by manufacturers and surface finishing providers. These include Alodining, anodizing, polishing, and powder coating. Alodine being a passivation technique is suitable for internal parts of aluminum projects. On the other hand, anodizing offers much-needed durability and protection for exterior parts. Alodine vs. anodize, what are the differences?
What is Alodining?
The use of a chemical called Alodine to create a protective layer over aluminum is called alodining. The coating sticks to the surface, lasting many years without requiring reapplication. In Alodining, the aluminum part is immersed in a tank, usually at room temperature.
Since it creates a chemical film, it requires minimal technical expertise and is less expensive. The chemical film coating allows aluminum to retain its thermal and electrical conductivity. Therefore, when you need parts that are to be electrically grounded, this is the process to go for.
Advantages of Alodine
There are many reasons manufacturers and surface finishing providers go for Alodine. These include:
- It is relatively a lower-cost process
- Offers improved protection against corrosion and scratches
- Gives a good electrical and thermal conductive surface
- Allows painting of aluminum
- No need for a primer and the paint sticks well
- Cleanup is not necessary after application
- It does not alter the dimensions of the parts
- Requires minimal skill
Disadvantages of Alodine
These are the common disadvantages of Alodine:
- The coating can be removed easily and can have micro-defects
- The procedure is not environmentally friendly as it is difficult to dispose of spent tank contents
- Getting into contact with Alodine can cause itching or rashes in people
What is Anodizing?
Anodizing is an electrolytic process that results in the formation of a protective layer on aluminum. The process follows the principles of electrochemistry. In this case, a workpiece gets immersed in an electrolyte solution and electricity is applied.
Aluminum serves as the anode and the acid releases oxygen ions due to electric current. Thus, the aluminum surface is transformed into aluminum oxide. The coating has enhanced durability and corrosion resistance properties.
Anodized aluminum has many applications in the cookware, medical, automotive, aviation, and military industries. Also, it is used in the manufacture of pharmaceutical and medical equipment and tools, such as sterilizers.
Advantages of Anodizing
Increased Durability
The truth is that anodized aluminum is more durable as compared to untreated aluminum. This is because anodizing creates a tough, protective layer that is resistant to dents, wear, corrosion, and scratches. Thus, anodized aluminum is perfect for use in applications that involve harsh chemicals, extreme temperatures, and rough handling.
Enhanced Aesthetics
Since anodized aluminum can be made in a range of colors, it is useful in applications where aesthetics matter. Moreover, anodized aluminum has a uniform, smooth finish that looks professional and polished. It has also been found to resist discoloration and fading over time.
Corrosion Resistance
Bare aluminum is less resistant to corrosion compared to anodized aluminum. This is because the aluminum oxide layer is naturally resistant to both air and water. It is less likely to deteriorate or rust over time. Thus, it is a perfect choice for applications where the part is exposed to moisture.
Disadvantages of Anodized Aluminum
It is an Expensive Process
Anodized aluminum is more expensive than bare aluminum. This is because the anodizing procedure is labor-intensive and time-consuming. Also, this finishing process requires skilled labor because it is complex. However, considering the durability of anodized aluminum, the additional cost is justified.
Limited Thickness
The other disadvantage is that the oxide layer’s thickness is limited. Although anodized aluminum is more corrosion-resistant and durable than bare aluminum, the oxide layer is quite thin. As a result, the material might not be resistant to certain forms of damage.
Welding Challenges
Anodized aluminum is more challenging to welding as compared to bare aluminum. You should note that the oxide layer is not electrically conductive, hence interfering with the welding process. As a result, special equipment and techniques are needed to weld anodized aluminum.
Alodine Vs Anodizing – What is the Difference?
The main similarity is that both Alodining and anodizing enhance aluminum’s corrosion-resistant properties. If your only aim is to protect your aluminum parts from corrosion without any technical requirements or budget constraints, you can choose any given method.
Since Alodining can serve as the primer, it is relatively inexpensive and allows aluminum to be painted. On the other hand, anodizing provides aluminum with a uniform coat but needs specialized equipment and skilled labor. As a result, it becomes more expensive.
Since both Alodining and anodizing involve electricity and chemicals, advanced safety measures are necessary. No matter the method you go for, proper equipment and training must be employed.
In summary, anodizing is an ideal surface finishing process for large-scale manufacturing as expenses can be minimized by mass orders. However, if you are handling small-sized orders or cheap components, then you should go for Alodining as it offers great properties at minimal production cost.
Other than being different finishing processes, product designers considering these processes must know the main differences:
- Design clearance consideration – Alodine creates a thinner film, while anodizing creates a thicker oxide layer. This will have an impact on designs where tight tolerances are required.
- Mechanical damage protection – Anodizing creates a thicker layer that is more corrosion resistant than the chemical film produced by Alodining.
- Aesthetics – Anodized aluminum can be dyed with a variety of colors. However, Alodined aluminum is only available in brown or clear colors.
- Sustainability and safety – Both anodizing and Alodining have similar impacts on the environment. Therefore, if sustainability is an important consideration, it is advisable to go for powder coating aluminum.
- Electrical and thermal conductivity – Anodized aluminum has ceramic-like properties that make it a poorer conductor of heat and electricity than an Alodine finish.