Metals like aluminum, magnesium, titanium, etc., have been employed in a number of industries, such as the automotive, aerospace, electronics, etc., because of their desirable properties. These applications, however, demand the employment of these metals in hazardous working conditions.
High humidity, high temperatures, the presence of acids and salts in a service environment, etc. are a few conditions that cause certain metals to lose some of their properties. This increases the cost of maintenance or component replacements by causing some metals to degrade under use.
Techniques have been developed to preserve these metals when used in these circumstances. Anodizing is one technique for shielding these metals from hazardous working conditions. It helps to increase the metals’ resilience, which minimizes the cost of component replacement and upkeep.
This article will discuss the different types of anodizing finishes, their uses and benefits, and the anodizing process. We will also provide answers to some of the most commonly asked questions about anodizing.
If you have any questions, please contact us with any questions about our anodizing process or request a quote today.
What Is Anodizing?
Anodizing is a process used to create a protective layer on the surface of a metal. It is a specific kind of electrochemical procedure that thickens the metal’s natural oxide layer before sealing it with a finish. Anodizing is frequently used to give metals a more appealing finish as well as increase their durability and resistance to corrosion.
Aluminum, titanium, and magnesium are just a few of the many metals that can be anodized. The procedure is relatively straightforward. It entails running an electric current through the metal while submerging it in an electrolyte solution. A protective oxide layer is created on the metal’s surface as a result of the reaction that this current sparks between the metal and the electrolyte.
The thickness of the oxide layer can be controlled by adjusting the current and the length of time the metal is exposed to the electrolyte. The layer can also be further sealed with a finish, such as a dye or a clear sealant. Anodizing is a relatively low-cost process that can be used to create a variety of finishes, including matte, satin, and gloss.
How Does Anodizing Work?
The anodizing process, the metal product must first be immersed in an electrolyte bath before an electric current can be sent through it. As a result, a thin oxide layer forms on the product’s surface, serving as a protective coating.
An electrolyte solution containing a metal salt, such as sulfuric acid or chromic acid, is used in the process. The next step is to connect the electrolyte solution to a direct current power source to run an electric current through the metal product. A thin coating of oxide forms on the surface of the metal product as a result of the electrolyte solution’s reaction with the metal as the current flows through it. The product’s protective coating is a result of this oxide layer.
The thickness of the oxide layer can be controlled by adjusting the voltage of the electric current and the type of electrolyte solution used. This makes it possible to create a variety of finishes, from thin, transparent layers to thicker, more robust layers. Moreover, anodizing can be utilized to produce a variety of colors, from brilliant hues to natural metal tones.
Anodizing Vs Electroplating
Anodizing and electroplating are two common surface treatments used to create a protective layer on metal substrates. Both procedures offer protection but differ in terms of the materials they employ and the outcomes they deliver.
An acid is used in the electrolytic passivation procedure known as anodizing to deposit an oxide layer on a metal’s surface. The metal itself is not as hard or corrosion-resistant as this layer. Furthermore, anodizing can be used to add decorative features like coloring or texture.
Electroplating, on the other hand, is a process that applies a thin layer of metal to the surface of a substrate. This layer is typically used to improve the appearance or performance of the substrate. It can also be used to prevent corrosion.
The main difference between anodizing and electroplating is the materials used. Anodizing uses an acid to create an oxide layer, while electroplating uses metal to create a thin layer. Anodizing is also more durable and resistant to corrosion than electroplating, making it a better choice for applications that require long-term protection.
Why Are Anodizing Finishes Important?
Aluminum that has been anodized is more corrosion-resistant than plain aluminum. Both regular and anodized metal cannot rust. Yet, they still have the potential to corrode when exposed to moisture, air, salt, or other substances or elements that prevent corrosion. Yet, because anodized aluminum has a thicker layer of oxide than ordinary aluminum, it is less likely to corrode.
Anodized aluminum has greater lubrication than ordinary aluminum, but its greatest advantage is undoubtedly its superior resistance to resistance. When aluminum is anodized, the metal’s pores are made deeper, which enhances the metal’s capacity to retain lubricating oil or film. Standard aluminum has a smooth surface, so it’s unable to retain lubricating oil or film.
In order to create colored aluminum items, anodized aluminum can also be colored. Dyeing is often not supported on standard aluminum. Companies that employ ordinary aluminum are, therefore, limited to using it in its natural chrome color. Luckily, anodized aluminum can quickly and effectively address this issue.
Anodized metal may be colored to any hue or mix of colors, unlike regular aluminum. How can dyeing be supported on anodized aluminum? Aluminum is exposed to substances that are acidic during the anodizing process, such as sulfuric acid, which causes a thicker oxide layer and a porous surface to form. Anodized aluminum’s porous surface makes it better able to take dye than ordinary aluminum’s smooth, nonporous surface.
Lastly, anodized aluminum has better adhesive and primer adherence. This is as a result of anodized aluminum’s oxide surface having larger holes than ordinary aluminum. When adhesive, primers, or liquids are applied to the surface, they will flow into the pores, which are essentially holes. Greater adhesion is possible thanks to the anodized aluminum’s ability to absorb liquids.
Disadvantages Of Anodizing Finishes
- Can only use specific grades of aluminum for this process,
- Cannot be used on Stainless Steel, which is durable to mortar, salt, chlorine and marine environments,
- This method draws from the base metal so it can be subject to color variations. In high grade metals a 95% match is possible between batches, in low grade metals no match is possible.
- Consequently harder to replicate consistency between batches compared to plating.
- The most expensive solution for small quantities (requires a higher-grade alloy in addition to the already high set up costs).
Types Of Anodizing Finishes
Anodizing is an electrochemical process that creates a protective coating on the surface of a metal object. This coating is usually a few microns thick and is made up of an oxide layer. Anodizing is used to improve the metal’s durability, corrosion resistance, and aesthetic quality. It is also used to give the metal a unique color or finish.
One of the most popular methods of anodizing, sulphuric acid anodizing is used to give aluminum and other metals a long-lasting, corrosion-resistant finish. In order to form an oxide layer, the metal is immersed in a sulfuric acid bath while being electrically energized. A lubricant is then used to seal this layer, giving it weather resistance and a glossy, smooth finish.
Because of its accessibility and efficiency, sulphuric acid anodizing is preferred for numerous applications. It has a smooth, attractive appearance, superior electrical insulation, and great corrosion resistance. It may be used on a range of metals, including titanium, steel, and aluminum, and is also rather simple to apply.
Chromic Acid Anodizing (CAA) is a type of anodizing process that uses chromic acid to create a protective layer on metal surfaces. Aluminum, titanium, and other metals are frequently treated with this kind of anodizing to strengthen their corrosion resistance. Because to its ability to produce a range of hues, CAA is often employed to develop decorative finishes.
Although the CAA procedure employs a different electrolyte solution, it is comparable to other forms of anodizing. Chromic acid electrolyte is the substance that CAA employs in place of sulfuric acid. Chromium trioxide and sulfuric acid are combined to form this solution, which is heated to a temperature of around 220 degrees Fahrenheit.
Once the electrolyte solution is heated, the metal is submerged in the solution and an electrical current is applied. This causes the chromic acid to react with the metal, forming a protective oxide layer on the surface. The oxide layer is porous and can be colored by adding dyes to the electrolyte solution.
CAA is often used to create a decorative finish, as it can produce a variety of colors. It also increases the corrosion resistance of aluminum, titanium, and other metals. The CAA process is more expensive than other types of anodizing, but it produces a higher-quality finish.
Bsaa (Boric-Sulfuric Acid Anodizing)
BSAA (Boric-Sulfuric Acid Anodizing) is a type of anodizing that uses a combination of boric acid and sulfuric acid to create a strong, corrosion-resistant finish. As it uses no hazardous heavy metals, it is a more environmentally friendly alternative than other forms of anodizing. Aluminum and titanium parts frequently have this form of anodizing applied to them because it works exceptionally well to prevent corrosion in these metals.
It takes two steps to anodize with BSAA. In the first step, boric acid and sulfuric acid are used to etch the metal surface, resulting in a porous surface. The anodizing solution may permeate the metal more deeply thanks to its porous surface, giving the metal a stronger and more durable polish.
The metal is subjected to a voltage in the second step, which causes the surface to become anodic and create a protective oxide layer. Because of its resistance to corrosion and abrasion, this layer is perfect for usage in demanding conditions.
The method of hardcoat anodizing, sometimes referred to as Type III anodizing, is used to give aluminum and other metals a thicker and harder coating. This kind of anodizing strengthens the metal’s wear resistance and offers excellent corrosion protection. In the hardcoat anodizing procedure, the metal is submerged in an electrolyte solution, and electrical current is run through it. This results in a chemical reaction that coats the metal with a tough, protective coating.
Hardcoat anodizing, also known as Type III anodizing, is a procedure used to give aluminum and other metals a thicker and harder finish. This kind of anodizing increases the metal’s wear resistance, and a high level of corrosion protection is offered. The metal is submerged in an electrolyte solution during the hardcoat anodizing process, and then an electric current is run through it. As a result, the metal develops a tough, protective covering due to a chemical reaction.
The hardcoat anodizing process can be used on a variety of metals, including aluminum, steel, brass, and bronze. It is also suitable for use on plastic and other non-metallic materials. The process is relatively quick and cost-effective, making it a popular choice for many industrial and commercial applications.
Titanium anodizing is a type of anodizing finish that is used to increase the durability and corrosion-resistance of titanium products. In contrast to other types of anodizing, titanium anodizing relies on the application of an electrical current to deposit a thin layer of titanium oxide on the product’s surface. Its titanium oxide coating gives the product a distinctive cosmetic appearance in addition to being extremely corrosion-resistant.
Titanium anodizing is commonly used for products such as titanium jewelry, medical implants, and architectural components. Also, it is utilized in the aerospace sector for parts that need high corrosion resistance, such as airplane components. The anodizing technique is perfect for products that need a distinctive look since it can be tailored to produce a wide range of colors and finishes.
Electrolytic 2-Step anodizing is a process that uses two different electrolytes to create a durable, corrosion-resistant finish on aluminum. In order to form a thin anodic layer, the aluminum must first be dipped into a sulfuric acid bath. A second bath of chromic acid is applied after this layer to produce a thicker, stronger anodic coating. The result is a significantly more durable finish than a single-step anodizing procedure.
When a thicker anodizing finish is required, such as when making a protective coating for aluminum parts that will be exposed to the elements, the electrolytic 2-step method is frequently utilized. The two-step process makes it possible to have greater control over the thickness of the anodic layer, which is advantageous for parts that need a more precise finish.
However, the electrolytic 2-step process is more expensive than a single-step anodizing process due to the additional cost of the chromic acid bath. Notwithstanding, the increased durability and precision of the finish make this process a worthwhile investment for many aluminum parts.
Color anodizing is a type of anodizing finish that can be used to add a decorative look to a product. The electrolyte solution is colored during the anodizing process to produce this particular anodizing finish. The dye is absorbed into the metal’s pores, giving the material a permanent color that won’t fade or chip. Covering the anodized finish with a transparent sealant can further improve the color.
Color anodizing is commonly employed to give items like jewelry, kitchenware, automobile parts, and architectural components a decorative flair. With color anodizing, practically any color is possible, and the technique can be utilized to produce a spectrum of finishes, from subtle to striking.
The color anodizing process is relatively simple and cost-effective, making it an attractive option for a wide variety of applications. However, it is important to note that the color of the anodized finish will be affected by the alloy of the metal and the type of dye used. It is also important to ensure that the anodizing process is properly carried out in order to achieve the desired results.
Anodizing Finish Process
Anodizing follows the same broad strokes as many other finishing processes. In practice, this means that you should follow this process:
- Prepare the surface
- Clean the parts
- Add color
- Seal the pores
Before you anodize a part, you have to prepare its surface through mechanical and chemical means. To give your part the desired aesthetic, polish or bead blast the surface first. While brushing will give your part a brushed appearance, bead blasting will give it a natural matte finish.
Next, place the part or parts in the anodization bath connected to the electrical circuit. The solution’s composition, temperature, current density, voltage, and time are just a few examples of the parameters that can change depending on the desired attributes mentioned above.
Clean the Parts
The part needs to be cleaned with deionized water and solvents after anodization. Remember to dry the component after. This removes any extra solution and prepares the part for the chromatic finish.
When anodizing, you can regulate the color of the component. Depending on the oxide coating’s thickness, the visible spectrum’s nanometer-sized wavelengths can reflect light in various ways. Many colors are produced using various parameters.
Put your part in a solution of metallic salts to give it a bronze or black polish. They interact with the surface to fill the pores with a chemical substance that is either black or bronze. It is known as electrolytic coloring.
Seal the Pores
To stop future corrosion and boost performance, you must seal the tiny pores on the component’s surface after anodizing. Anodized parts may feel tacky to the touch if the pores are not sealed. Furthermore, dirt, pollutants, and stains can gather in open pores.
Common Uses Of Anodizing Finishes
Anodizing is a versatile finish that can be used in a variety of applications. It is often used to improve product durability, corrosion resistance, and aesthetic quality. Anodizing can be used on a variety of metals, including aluminum, titanium, magnesium, and zinc. It is also used in the production of electronics, automotive parts, and medical devices.
Aluminum is usually treated with anodizing to prevent rust and wear. Products that are exposed to severe surroundings, such outdoor furniture, window frames, and boats, frequently have the finish applied to them. Cookware, jewelry, and aluminum auto parts can benefit from anodizing to make them look better.
Anodizing can also be used to improve the performance of electronic components. Circuit boards, connections, and other electronic parts frequently have the finish applied to them in order to prevent corrosion and increase electrical conductivity. Medical equipment like implants and prostheses can benefit from anodizing to operate better.
Anodizing is often used to provide objects with attractive finishes. Several colors, textures, and patterns can be produced with the finish. Anodizing can be used to produce a variety of finishes, from metallic to pearlescent and matte to glossy. A variety of decorative patterns, including stripes, swirls, and geometric forms, can also be made with the finish.
The major purpose of anodizing is to improve the following properties in the metal that’s been anodized, these properties include: wear resistance, corrosion resistance, surface lubricity, heat dissipation, dielectric (non-conductive) properties, adhesion, and aesthetics. These properties are very important to businesses that employ these metals ( Aluminium and its alloys ) in service, helping them save hundreds of thousands of dollars in maintenance and component replacement costs.
If your business needs functional aluminum parts that will face corrosion or wear, such as aircraft parts or consumer goods, contact us, and we’d be more than happy to help.
Please check us out with any questions about our anodizing process or request a quote today.
What is the 720 rule of anodizing?
The 720 rule of anodizing is a rule of thumb that states that the thickness of a given anodized finish should not exceed 720 millimeters. This rule is especially important when it comes to anodizing aluminum, as this type of metal is particularly susceptible to corrosion. The thickness of the anodizing should be kept in check to ensure the finish’s longevity and prevent corrosion.
Does anodizing wear off?
Anodizing does not wear off, as it is a permanent finish. However, it can be scratched or damaged if not properly taken care of. Anodizing is a strong and durable finish, but it is not indestructible. It is important to take the necessary steps to protect an anodized finish, such as regular cleaning and maintenance.
Which is better non stick or hard anodized?
The type of anodized finish that is best for you depends on your needs and requirements. Non-stick anodizing is a great option for cookware, as it creates a slick and non-stick surface that is easy to clean. Hard anodizing, on the other hand, is more durable and is often used for industrial applications.
Is an anodized finish durable?
Anodized finishes are incredibly durable and resistant to corrosion, making them ideal for a variety of applications. Anodizing is a permanent finish that can last for years, even in harsh environments. It is also resistant to scratching and other types of damage, making it a great choice for products that need to stand up to wear and tear.
Can you anodize all metals?
No, not all metals can be anodized. Metals such as aluminum, titanium, and magnesium are the most commonly anodized, as they are the most receptive to the anodizing process. Other metals such as steel, brass, and copper can be anodized, but the process is more difficult and the results may not be as effective.