Alodine vs Anodize, A Comprehensive Comparison

Before starting the comparison between Alodine and anodize, you must know what actually are these? Well, these are two types of finishing for Aluminum. Alodine is basically a trademark name for a certain chemical. This is also known as chromate conversion and chemical film. So, if these terminologies are used anywhere, now you know they are representing Alodine finish. These surface finish sometimes get confusing for the person who has not enough knowledge about coating and finishing. This article will provide necessary information about Anodize and Alodine process. The comparison between them is described by their processes, pros and cons, properties, and applications. We hope this information will give you enough information about deciding the best finish process for your project.

Overview

Alodine and anodize are different processes. Since anodizing is an electrochemical process while Alodine is a chemical film. Alodine process does not involve any type of electric current. In fact, the aluminum products are cleaned and then immersed in a chemical bath at room temperature and a protective thin film of chromium is formed over the surface. other than immersing the object, spraying and brushing are also used for surface finish process but immersing is a common and easy technique. Thin film is created in a matter of minutes and a uniform thickness is obtained easily and then the object is rinsed and dried. Protective film is softer initially but gets harder after drying. However, anodizing has greater hardness and strength than Alodine.

While anodizing has an anode in an electrochemical process in the solution of sulfuric acid. Aluminum film is produced over the surface of an object which is hard and thick and naturally creates an aluminum oxide layer.

Cleaning of part before the finish is highly important in both anodizing and Alodine coatings. Degreasing is done thoroughly, and sometimes acid etching is also carried out in anodizing.

Coating is very uniform, and no process create opaque coating like paint or powder coating. Material surface finish has no imperfections. In case appearance is important, the desired texture is created before the process. Famous techniques are brush finish and blasted finish that are in demand and are done before the process to get uniform texture.

What is Alodine?

Alodine is a chemical used to create a protective layer on Al objects. and thus, the process is called Alodining. Coating adhesion is good to the surface and has a life span of decades and requires no further special treatment. Aluminum objects are submerged in the coating tank at room temperature. Special training and technical expertise are required because it is a chemical film, but it is an economical process. Coated aluminum is able to retain its electrical and thermal conductivity. Therefore, this is a preferred coating process when the part has further application in being electrically grounded.

Alodine finish

Alodine coating is famous for aluminum objects because it is economical and imparts high electrical conductivity. Bue due to some limitations, it is sometimes not preferable. The durability of Alodine finish is less and has low corrosion resistance. The coating color is less consistent than anodizing. In spite of these drawbacks, it is a best option for high stress and aggressive atmosphere applications.

Anodize Definition

Anodizing is an electrochemical process, and a protective layer is formed over the surface finish as a result of the process. The principle of electrochemistry is followed, and process requires an electrolytic solution and electrical current is applied and the object to be coated is immersed in the solution. Anode is aluminum and the acidic bath of sulfuric acid releases oxygen ions because of the current. Therefore, the aluminum surface finish is coated with aluminum oxide which has high durability and high corrosion resistance and wear resistance.

Anodized aluminum is an in-demand product and frequently used as cookware in the medical field, automotive and aerospace industries. Anodized aluminum objects are easy to clean therefore, medical or pharma equipment like sterilizer are made of it.

Anodize Aluminum finish

Anodize aluminum finish is normally carried out in chromic acid and sulfuric acid. For the applications in aerospace industry, the anodize part finished with phosphoric acid, boric acid mixed with sulfuric acid.

Properties of Alodine vs. anodize

Alodine and anodize has exceptional properties which are explained below:

Durability and longevity

Due to being durable anodizing and Alodine finish is mostly used for aerospace parts such as wing panel, landing gears and engine components. They perform best in military aircraft application. Both coatings have great resistance to surviving harsh and aggressive environmental conditions and can stay consistent throughout the lifetime. Anodizing, however, performs better when compared with Alodine coating. But the application of anodizing and Alodine finish is now common in aerospace industry due to versatile coating and high durability and long lifespan.

High saltwater and corrosion resistance

Corrosion and salt resistance are a big issue in marine and aerospace industry because saltwater rain or other pollutants in environment can affect adversely on the components of ship and aircraft. Anodizing and Alodine coating both create a protective oxide layer against these atmospheric conditions which is great corrosion resistance and prevents the object being damaged. Alodine furthermore, protect the surface finish from wear and tear and decaying.

High electrical and thermal Conductivity

Thermal conductivity is an important factor is aerospace industry for optimal performance of engine parts that require efficient heat transfer. Electrical conductivity has also same importance as these properties if disturbed during finishing, may have adverse effect during functioning. Anodizing and Alodine processes do not affect the thermal and electrical conductivity of parts. This finish helps to maintain thermal and electrical performance and at the same time protects it from wear and corrosion.

Alodine vs Anodize: What are the Similarities

The similarities between anodizing and Alodine coating are:

• Both require electrolytic solution or acidic bath to immerse the object for coating
• Both methods require the deposition of object to be coated
• Uniform coating is applied in both processes unlike opaque coating like paint and powder coating
• Both help the material or retain their original properties like thermal or electrical conductivity
• Durability is high and both require no further special treatment to be consistent
• Corrosion resistance of both coating is very high along with wear resistance

Alodine vs Anodize: What's the Difference

Alodine coating is a primer, and it is economically viable, and aluminum can be painted afterwards. While anodizing provides a uniform protective oxide layer and needs special training and skilled labor to perform the task. And thus, it is an expensive process.

Anodizing requires extra safety measures as it involves current and dangerous chemicals. Alodine also needs safety measures, but simple training can train the labor and it is simpler process than anodizing. Still, poor labor and wrong equipment handling in any of the process can leave disastrous effects.

Anodizing is ideal for large scale production because the expenses become minimized due to huge orders. For small scale production, Alodine is better because it has less production cost.

The protective layer created in Alodine is thin while anodize has thick oxide layer which ultimately influences tolerance in designs.

A thicker anodizing oxide layer protects the metal from many mechanical damages and thus object has better mechanical properties. In Alodine process, protective layer is soft initially but gets harder. Still its hardness is less than anodizing and has weaker mechanical properties.

Anodized parts have a huge color selection which increases its aesthetic demands. Alodine coating is normally in brown color or clear colors.

Applications of Anodizing and Alodine

Anodizing and Alodine finish have many applications in all fields.

Aerospace industry

Anodized and Alodine finish components are highly demanded in aerospace and space industries because they are highly durable and have long lifespan. Their corrosion resistance is excellent, and they have the ability to reduce friction. Application of Alodine is normally at places which are less exposed and requires precise fit.

Military industry

Alodine coating and anodizing is best for military and defense devices. Especially anodizing is preferable where corrosion resistance is required and no need for any further coating treatment is required.

Construction

Anodize aluminum is demanded in construction and architectural industry as it increases the aesthetic appearance and can stay without being damaged for a long time.

Marine industry

saltwater and ocean environments are the most corrosive places and part becomes quickly corroded as compared to other environments. Anodizing offers best corrosion resistance properties for these types of environments.

Automotive

Highly durable anodized coating offers better services for the parts used in automotive industries. They are also easy to manufacture.

Electronics

Anodize and Alodine coating both provide the best electrical insulation feature and helps the material to retain its electrical conductivity after the finishing. This feature is highly in demand in the electronic industry.

Pros and Cons of Alodine and Anodize

Advantages of Alodine finish

Alodine offers many features that are useful in many ways. These include:

1. It is an economical and cost-effective process
2. It offers the best corrosion resistance and scratch-free process
3. Provide excellent electrical and thermal conductivity of product
4. Offers painting for aluminum surface
5. Coating adhesion is best and requires no further primer or paint
6. Cleaning is not required after finishing
7. Offers dimensional accuracy and does not change the dimensions after finishing
8. Little training and minimum skilled labor are required

Disadvantages of Alodine finish

Alodine also has some drawbacks which are:

• Coating has microdefects when it is removed
• Surface finish the process is not environmentally friendly and disposal of tank contents is difficult
• Safety measures are necessary to take because it leaves itching and rashes to skin

Advantages of Anodizing

• The durability of anodized aluminum is much higher than aluminum
• High corrosion resistance, wear resistance and scratch free coating
• Preferable for the applications at areas with high aggressive environment, chemical and high temperature
• Provide a variety of colors and more appealing aesthetically
• Smooth finish with uniform thickness
• Offer discoloration resistance and does not fade overtime
• Saltwater and oxidation resistance is high

Disadvantages of Anodizing

• It is a relatively expensive process compared to untreated aluminum
• Requires specialized labor and a time-consuming process
• Process has complex steps and requires skilled labor
• Offer limited thickness therefore limited to few applications
• Weldability is less and the oxide layer is not conductive, so the welding process is difficult

When to Choose Alodine or Anodize in Aluminum

Alodine coating and anodizing both offer the best features and sometimes it gets difficult to decide which one to choose. In their selection, there are several factors that need to be considered. If you require high durability, corrosion resistance and wear resistance, then choose anodizing. The base for painting or coloring is better in anodizing. However, it is an expensive process. If you have a low budget, then Alodine coating is a better choice. Almost all the features of anodizing are also present in Alodine process. It is also a good option where electrical conductivity is concerned.

Conclusion and Recommendations

Alodine coating used chromic acid for coating and the object submerged in the solution. Anodizing is an electrochemical process and sulfuric acid is used as solution. Anodizing provides a thick protective layer of coating and offers high corrosion resistance and wear resistance to the object. Alodine is durable in some application than anodizing. Alodine coating is a cost-effective process and requires no expensive equipment and skilled labor while anodizing is a complex process and needs skilled labor to operate expensive equipment. TUOFA offers the best services in Alodine coating and anodizing. Tuofa has years of experience and skilled labor to operate special equipment for any services. For more information about Anodizing or Alodine coating, please visit our website: www.tuofa-cncmachining.com

FAQ

Is Alodine dangerous?

Yes, chromic acid used in Alodine coating could be dangerous if inhaled and cause irritation and burns to respiratory system.

Is Alodine conductive?

Alodine coating provides high thermal and electrical conductivity. Chrome coating of aluminum is preferable where conductivity is concerned.

Iridite vs Alodine

Alodine is a trademark name used for a chemical in coating. Iridtie is trademark name for chromate conversion process. They have variations like liquid vs. dry, color vs clear etc.

How to Alodine aluminum

Diluted Alodine is applied to aluminum as an acidic bath solution. Large area can be handled easily as it considers 6-10ft area as a single surface.