Alodine vs. Anodize: What You Should Know

What is Alodine?

Before we jump into the topic of alodine vs anodize, lets try to understand what is alodine and anodize. Actually, the product is marketed under the name “Alodine.” The term “chem film” or “chromate conversion coating” is used more commonly to refer to the process of alodining. In addition to anodizing, the metal will be passivated and protected from corrosion by chem film.

The procedure begins with applying a layer of a chemical known as alodine to a piece of metal. The material is basically submerged in a tank containing the prescribed solution while it is allowed to remain at room temperature. It is not necessary to apply any sort of electrical force. The protective layer that alodine produces can continue to function on its own for many years. A variety of techniques can be used to apply chem film to a surface or substance. As a result, applications can be made by dipping, brushing, spraying, and other methods. The convenience of one method of chromate conversion coating over another will determine which option is selected. Alodining has a wide range of potential applications, some of which are hardware made of aluminium, automobile wheels, the hulls of aircraft, torsion struts, and flight control systems, amongst other things.

Alodine Is a Corrosion Inhibitor

The chemical compound known by its trade name alodine is a corrosion inhibitor that is used in a variety of applications. It is an organic compound that is water-soluble and is used to coat metal surfaces in order to protect them from the effects of corrosion. You can purchase it in a powdered form that, once combined with water, can be used, or you can buy it already mixed up. It may be used on any kind of metal, including stainless steel, copper, aluminium, brass, or bronze without causing any damage to the surface. The primary function of alodine is to prevent corrosion of metals and metal alloys. A chromate conversion coating of this kind is what you’ll find on the metal’s surface after it has been treated. The action of alodine consists in the formation of a protective barrier on the surface of the metal, which stops corrosion from taking place. Because it attains the same degree of brittleness as the metal to which it is applied. In addition to preventing corrosion, a product’s durability can be increased by adding alodine.

The chemical bonds that alodine forms with the surface of metals result in a coating that is resistant to corrosion. The process does not have any effect on the pre-existing qualities of the metal, such as its weight or its degree of brittleness. In comparison to the original metal, an alodine finish offers superior protection against corrosion and even offers enhanced defence against chlorine gas.

Clear Alodine Coating for Aluminium

Aluminum components can be protected from corrosion by undergoing a chemical process known as alodic oxidation, which results in the application of a clear alodine coating. The coating of alodine aluminium chromate is produced by first soaking the aluminium component in a bath of chromic acid and then rinsing it with water. This process creates the coating. Chromic acid is the chemical solution that is utilised during the process of applying alodine. After being sprayed with clear alodine, a layer is produced that, once it has dried, becomes more rigid. It is frequently utilised for the production of wheels, window frames, and grills made of aluminium.

Clear Alodine Coating for Stainless Steel

A transparent alodine coating, very similar to the coating that is used on aluminium, is applied to the components that are made of stainless steel. This coating produces a surface that is nonporous, uniform, and resistant to rust and the majority of corrosion. It accomplishes its goal by means of a chemical reaction that takes place at a temperature of 600 degrees Celsius and involves the surface of the steel as well as the alodine. After the coating has formed and been cleaned, it is then stripped away. The surface of the steel is given a coating of protection as a result of this process.

What kind of surface coating does alodine have on aluminium components?

The term “alodining” refers to the process of first covering a metal with a material called alodine and then alodining the metal itself. Because it dries and becomes part of the surface, this coating can resist wear and tear for a good number of years without needing to be reapplied.

Pros of Alodine

• A method that is not expensive.
• Because it acts as a primer, it makes it possible to paint metal surfaces.
• It provides excellent protection against corrosion and shields even when scratched.
• It creates a surface that is highly conductive to electricity.
• Paint adheres well to it, and in some situations, you can use it in place of primer.
• It doesn’t add much weight.
• It does not affect the proportions of the components in any way (does not reduce the size of holes).
• Does not demand any sort of cleanup following its application
• Does not require any prior experience or the use of electricity.

Cons of Alodine

• If the temperature of the tank is lower than 70 degrees, the faren height calculation should not be used.
• The alodine surface is not as long-lasting as one that has been painted or anodized.
• You cannot alodine parts that have been assembled (nor can you anodize them.)
• It is a challenge to get rid of the contents of the used tank.

How Should Aluminum Parts Be Coated With Aluminum?

• Acetone can be used to remove residue such as glue, ink, and other substances from the component parts.Alclad uses a fine scotch-brite pad to remove any shine from the parts by rubbing them with it. If the parts are at all shiny, Alclad does this. Scotchbrite products such as discs and polishing wheels should be used to remove the oxide layer in a vigorous manner if the component in question is an extruded angle that is not clad. Scotchbrite rubbing is not required for Alclad parts that form into ribs and bulkheads and have a finish that is dull because these parts do not need to be polished. Additionally, scotchbrite is not required for newly machined components.
• Scrub exclusively in dish detergent until completely clean ( Attempting to use another detergent will result in absolute failure.). After washing the component, a continuous layer of water can be seen on its surface. If there are some areas where the water film does not cover, this indicates that there is grease on the item, and we should wash it once more.
• The component should remain submerged in the acid bath for about three minutes.
• Rinse by dipping it in a barrel containing acidic rinse.
• Immerse the part in the alodine tank for three minutes, turning it around once every thirty seconds while it is in the solution.
• Rinse should be dipped into the alodine rinse barrel.
• Think about using a blow dryer on the part to prevent drip marks.
• It is best to avoid rough handling of the component for the first 12 to 24 hours, as the fresh alodine film is easily damaged. However, the film will eventually harden.

Uses of Alodine Coating

Aluminum components with a clear alodine finish have found use in a wide variety of applications, including but not limited to those involving CNC machining, aircraft structures, engine components, electrical devices, automotive interior trim, and more.

CNC MachiningAluminum is a popular material choice for CNC machining parts due to the qualities it possesses. Without affecting the dimensions of the metals in any way, the process results in products made of metals that are resistant to corrosion. In CNC machining, alodine finishing offers a number of benefits, including improved adhesion during priming and the ability to adjust the conductivity of coatings. Other advantages include.

1. Aircraft Industry

In the manufacturing of aerospace products, alodine coatings are utilised to protect aircraft from oxidation and corrosion while also providing the desired aesthetically pleasing finish. Coatings made of alodine can be applied to various parts of aeroplanes, such as the hulls, landing gear, and shock absorbers.

2. Automotive Manufacturing

The alodine finish is typically applied to bumpers, grilles, and other components of an automobile’s exterior body. This is the most common use of this type of finish in the automotive industry. This contributes to the car’s overall appearance of being sleek and shiny.

What is Anodize?

A metal undergoes a finishing process similar to this one, in which a coating that is resistant to corrosion is formed on the metal. The fundamental ideas of electrochemistry serve as its foundation.

An acidic electrolyte solution is introduced to a workpiece, which is then subjected to an external electrical force while being immersed in the solution. An electrochemical reaction is started when an electrical current is passed through an electrolytic liquid and applied stress to a metal. In this process, the role of the anode is played by metal. In their own right, oxygen ions, which were liberated from the acid bath as a result of the electrical current, transfer onto the substrate and incorporate themselves into it.

As a direct consequence of this, the surface of the metal will change into an oxide layer. The coating that was obtained has improved properties in terms of its resistance to corrosion and its durability. The defence industry, the aerospace industry, and the automotive industry all contributed to the development of anodized aluminium components. This material is widely used in the production of tools and equipment units for use in the medical and pharmaceutical industries at the present time, such as sterilisers.

What is the surface coating for anodized aluminium parts?

The process of anodization involves submerging metals in salt solutions while simultaneously passing an electric current through the components. This results in the formation of a protective coating because it draws metals out of the salt and onto the surface of the metal.

Pros of anodizing coating

• Gives protection to the metal of a uniform coating.
• In comparison to paints and powder coats, the coating is extremely thin, measuring between.0002-.0012 inches. When it comes to machined parts, we can almost disregard the thickness.
• Extremely long-lasting, abrasion-resistant, and hard with a high level of durability.
• The coating is resistant to chipping and peeling.
• The coating will remain in place forever.
• Provides excellent protection against corrosion.
• Maintains its integrity after being subjected to a salt-spray and other tests.
• Simple inorganic chemicals that have a negligible effect on the surrounding environment are used in the manufacturing process of the finish, making it environmentally friendly.
• Powder coating and painting both have prices that are comparable to this one.

Cons of anodizing coating

• We are required to use specialised equipment (the cost of the facilities is high), and we need to lower the amount of pollution in the environment.

Electricity and chemical reactions are involved in these processes. Therefore, we need to focus more of our attention on the safety precautions. In addition to this, we are responsible for conducting the necessary training and checking the equipment.

How Can I Tell the Difference Between Anodize vs Alodine Coatings?

Anodizing and alodining the surface of certain metals are both chemical processes that are used to produce an oxide protective barrier. Alodine surface coating is also used. When this barrier is applied to metals such as aluminium parts, it acts as a protection against corrosion and prevents the metals from rusting. The process of anodizing versus the process of applying an alodine coating is what differentiates the two in terms of both the cost and the barrier. Etching the metals that have been treated with alodine is the first and most important step in the preparation process. As a result, in order to prepare an anodizing surface, it needs to be cleaned thoroughly and immersed in a tank of saltwater. Anodizing and alodining are two different processes that can be used to protect magnesium and aluminium surfaces from corrosion. Since the processes for applying the protective coating are different, but the results are the same, we can conclude that the processes are equivalent.

What distinctions can be made between anodize vs alodine?

Let’s go over the specifics of what sets anodize vs alodine apart from one another. The primary similarity between these two types of finishing processes is that they both improve the material’s ability to resist corrosion. There is also a substrate that is compatible with the application of either coating without posing any challenges. This metal is aluminium. As a consequence of this, if you need the part you machined from aluminium to be protected from corrosion and there are no specific constraints on your budget or requirements from a technical standpoint, you are free to choose any coating method you like.

In contrast, there is a very long list of distinctions between the two. They are helpful in defining the circumstances under which one method is superior to another. The foundation of each method is a collection of distinct procedures, each of which has a varying level of complexity. As a consequence of this, alodining has the upper hand in comparison to anodizing in terms of cost-efficiency. On the other hand, if the longevity of the coating is the primary concern, anodizing is a significantly better option than alodine, which loses its colour quickly. Therefore, you should go with alodining if you have a restricted budget and do not anticipate that the component you have manufactured will last for many years. You ought to go with anodizing if the circumstance is exactly the opposite of what you were expecting.

1. Preparation

First, the metals that will be treated with alodine need to be etched with acid. A surface that is going to be anodized needs to be free of any debris before it can be placed in a tank filled with salt water.

2. Process

Metals that have been etched with acid can either be submerged in a tank that contains alodine or painted with the chemical. The coating that results from dipping is the most even, but either technique needs to be dried using hot air under pressure. The process of anodizing is a challenging example of electrochemistry. The reaction is started by inserting electrodes into the salt water tank after the anodizing chemicals have been added to the tank.

3. Finish Effect

The surface of the metal is given a thin barrier by the coating of alodine that it receives. Anodizing is similar to coating the surface with a film, but it goes deeper into the metal, creating a barrier that is significantly thicker. It also has the additional effect of making the material more durable.

4. Cost

It is easier and less expensive to apply alodine because it only requires painting the surface or having enough of the chemical to submerge the metal. Additionally, the supplies for alodine are more reasonably priced. Anodizing requires the use of significantly more expensive chemicals as well as electro-chemical bath equipment. The process of anodizing involves greater risk and calls for a higher level of expertise than alodining. 

Some advantages of an alodine finish vs anodize finish include the following:

• Alodine is available at a lower cost than anodize.
• Clear alodine can be used on a wider variety of metals than its counterpart.
• Finishing with alodine is not quite as long-lasting as finishing with anodize.

Alodine finish has the following drawbacks over anodize:

• Alodine will scratch and tarnish more readily than anodize.
• Only clean surfaces devoid of oils and greases can be treated with alodine.
• Alodine will not stick to some metals.

References

How To Know The Difference Alodine and Anodizing Coating? (2019, July 4). CREATINGWAY. https://www.creatingway.com/alodine-and-anodizing-coating/

Anodize vs. Alodine: What’s the Difference? (2022, October 16). EcoReprap. https://ecoreprap.com/anodize-vs-alodine/

Alodine Vs Anodize: Which Is The Best Aluminum Surface Treatment? – Xin Tian Jian Precision Mfg Ltd 2022. (2022, April 5). Xin Tian Jian Precision Mfg Ltd. https://cncpartsxtj.com/surfaces-finishes/alodine-vs-anodize-which-is-the-best-aluminum-surface-treatment/

Lawrence, R. (2021, November 20). How to Apply Epoxy Metal Paint. HomeSteady | the Ultimate Guide for All Your Household Needs. https://homesteady.com/how-6023372-apply-epoxy-metal-paint.html