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Alodine coating, also referred to as Yellow finish, is an industrial process that is used for surface finishing. It preserves the surface of the metal and prevents corrosion.
Alodine Surface Finishing
The manufacturing industry faces a strict challenge which is corrosion and surface damage. This leads to the failure of machined parts concerning accuracy and precision. To cater to this issue, parts manufacturers implement various measures such as compounding and painting. However, among the top solutions to this problem is Alodine coating. The process of Alodine coating significantly improves the manufacturing of machining parts. Also, referred to as Alodine finish, it has many design considerations across the industry. This article will discuss the process of Alodine coating in detail, highlighting its use cases and advantages.
What is Alodine?
Alodine chem solution
Before diving deep, let’s first understand what Alodine is. It is a chem film coating that serves the primary purpose of protecting metal from corrosion. It is mainly used for coating aluminum as it protects the nature of the element from the outside environment and serves as the base for painting coats as well. Alodine chem film has different names in the industry. Some manufacturers also call it Iridite coating, while others refer to it as Yellow Iridate due to its yellowish color. To apply this chem film, industrialists use different means including dipping, brushing, and spraying the compound directly to the metal surface. It can also be combined with Anodizing (Type II) to reconstruct the small damages to the metal surface.
Different types of Alodine coating vary in chemistry and are used for different types of metals.
● MIL-DTL-5541
● MIL-C-81706
● AMS-C-5541
● AMS-2473
● AMS-2474
All these chem films are industrial and serve high importance in increasing the component lifespan. However, the most consumed types of chem films are MIL-DTL-5541 (Type I and Type II).
Why is Alodine Coating Important?
Alodine-coated parts before & After
Alodine coating is important for the durability of metal and its age. It not only protects the metal from corrosion but also serves as a baseline for painting and other types of coating such as chromate. Various industrial applications use Alodine coating to benefit from its wide range of benefits including aircraft manufacturers, and automotive production houses. This coating is applied on aircraft hulls, shock absorbers, and landing gear to improve the adhesion of paint and premier.
Characteristics of Alodine Finish
Alodine coating is a common industrial finishing process that is simple and allows for preserving the metal surface. Below are some of the key highlights that make this chemfilm best to consider.
Film
Alodine film on the aluminum part
One of the key characteristics of alodine film is its thin coating which is usually between “0.5 to 4 microns”. It acts as a corrosion-resistant coating that preserves metallic properties without any alteration. This thin film also acts as a primer or base.
Temperature
Different types of Alodine films react differently to temperatures. The type 2 standard is best for room temperature which is why manufacturers use it to apply coating over metals.
Solution Nature
Different solutions of alodine come with variable nature. Some are toxic such as the hex chrome alodine coating.
Use-Cases of Alodine Coating
Alodine coating offers a significant increase in metal’s overall nature, increasing its lifespan, and usability while offering high-grade protection. When applied to aluminum alloys, alodine finish enhances the characteristics of the metal for the manufacturing of different industrial components. Here are some use cases of Alodine coating.
CNC Machining Parts Manufacturing
CNC-machined alodine-coated parts
CNC machining parts manufacturing uses Alodine coating to preserve the metal for long-term use. This makes the metal resistant to corrosion without any sort of alteration to the dimensions making it beneficial for CNC machining. Another benefit comes at the time of adhesion and priming of the parts where this chem film helps without impacting the conductivity of the metal.
The Aerospace Industry
The aerospace industry uses the Alodine coating to enhance the nature of metals that are used in various aircraft components. The advancement of technology has changed the way Type II of MIL-DTL-5541 performs on metallic surfaces making the process faster.
Aloding coating applications in aerospace
This also reduces the number of steps in the application process. Room temperature requirement is also optimal for the application which is not much hotter compared to Type I.
Alodine vs Anodized Aluminum Parts
Anodizing is often mixed with Alodine as both these terms are used interchangeably in the market. But the similar-sounding names, don’t mean that both are the same operations. While Alodining is a completely chemical operation, anodizing is concerned with electro-chemistry. It is an electrochemical process that requires current and various chemicals to enhance the nature of the metal while preserving the surface of aluminum parts. In anodizing the aluminum should be completely submerged in the chemical bath with a calculated electrical current applied to it that triggers the electro-chemical process. Here are some key differences between both processes.
1. Mechanical Damage Protection:
Anodizing forms a layer that has a ceramic-like composition that is highly wear-resistant while chem film or Adoline forms a coating for corrosion prevention.
2. Electrical Conductivity:
Because the ceramic-like anodized layer has poor electrical conductivity, it makes anodization an inefficient operation for conductivity. On the other hand, Alodine coating has comparatively higher electrical conductivity.
3. Coloring:
Alodine-coated colored parts
The anodizing process forms a porous aluminum oxide layer that can be dyed into a variety of colors. In contrast, the Alodine coating is either golden or brown. This means it can act as a primer before applying other paints onto the surface of themetal.
4. Cost:
Alodine coating is easier to maintain and comes at an affordable cost, while the anodizing process is costly. Moreover, it also requires technical expertise tooperate correctly.
Final Thoughts
To conclude, alodine coating is one of the top finishing processes that is used industrially, boasting the productivity and quality of the metal surface. It helps preserve the surface of the metal, makes it anti-corrosive, and acts as a base primer. It has a wide range of applications and is ideal for precision coating of aluminum alloys. From CNC machining parts protection to key coating in the aero space sector, Alodine is the go-to choice for large-scale manufacturers.
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