The key difference between anodized and alodine is that anodized describes an object that has undergone an electrolytic process, whereas alodine describes an object that has not undergone an electrolytic process.
Anodizing and alodine are two processes useful in aluminum finishing for the improvement of corrosion resistance. Both these processes can transform the outer layer of the surface of a metal into a proper structure. Typically, their results are similar, but the processes are different, especially the method of applying the protective coating.
CONTENTS
1. Overview and Key Difference
2. What is Anodized
3. What is Alodine
4. Anodized vs Alodine in Tabular Form
5. Summary – Anodized vs Alodine
What is Anodized?
Anodized metals are metal surfaces that have undergone the anodizing process. This process involves the laying of the metal in a solution of salts and then running a current through it. The passing of this current can attract metals from the salt to the surface of the metal. This can create a protective coating.
Anodizing is the process of electrolytic passivation that is useful in increasing the thickness of the natural oxide layer on the surface of metal parts. We call it anodizing because the object that is subjected to the treatment is used as the anode electrode of an electrolytic cell.
Figure 01: Anodized Parts
Anodized metal surfaces show higher resistance to corrosion and wear. It also provides better adhesion for paint primers and glues when compared to bare metals. Moreover, anodic films can be used for several cosmetic effects. This can be with thick porous coatings that are able to absorb dyes or with thin transparent coatings that can add reflected light wave interference effects.
Furthermore, the anodizing process can be used to prevent the galling of threaded components and make dielectric films for electrolytic capacitors. Most commonly, this method is used for the protection of aluminum alloys as well as for titanium, zinc, niobium, magnesium, zirconium, hafnium, and tantalum.
What is Alodine?
Alodine metals are metal surfaces that have undergone an aldoning process. This process involves the coating of the metals with a chemical named Alodine. This coating can harden on the surface, and it can last for many years if it is painted on the surface. Then it does not require re-application. More precisely, this is a chromate conversion coating that is able to protect aluminum and other metals from corrosion.
The composition of Alodine can be given as chromium(IV) oxide, sodium silicofluoride, barium nitrate, and ferricyanide. This process is very important in the aluminum industry, and it is also known as a chemical film or yellow iridite. The commercial trademark of this process is Iridite and Bonderite, which is formerly named Alodine.
What is the Difference Between Anodized and Alodine?
Anodizing and Alodine are two processes useful in aluminum finishing for the improvement of corrosion resistance. The key difference between anodized and alodine is that anodized refers to objects having undergone the electrolytic process, whereas Alodine refers to objects having undergone the electrolytic process. Moreover, anodizing requires specialized equipment to carry out the process, whereas alodine process does not require any specialized equipment. Therefore, anodizing is an expensive process, while aldoning is comparatively less expensive.
Below is a summary of the difference between anodized and alodine in tabular form for side-by-side comparison.
Summary – Anodized vs Alodine
Anodizing and alodine are two processes useful in aluminum finishing to improve corrosion resistance. The key difference between anodized and alodine is that anodized describes an object that has undergone an electrolytic process. In contrast, alodine describes an object that has not undergone an electrolytic process.
Reference:
1. “Alodine Finish: A Guide to Conversion Coatings for Precision Machining.” Rapid Direct, 2 Aug. 2022.
Image Courtesy:
1. “Cheap carabiners” By User:Polyparadigm – Own work (Public Domain) via Commons Wikimedia