Aluminum anodizing is an electrochemical finishing process where parts made of aluminum are finished to improve their hardness, corrosion, and wear resistance. Aluminum material has an oxide layer on it. However, this layer is uneven and provides poor wear and corrosion resistance. Anodizing helps create a uniform oxide layer over the material and improves its wear and corrosion resistance. The layers can be subjected to additional secondary processing to improve their functional properties. There are several types of anodizing and each one offers several benefits. This post introduces you to these types, the process itself, applications, benefits, and more.
Types of Anodizing
Our aluminum anodizing line is designed to support different types of anodizing. The following are a few common ones among them.
- Chromic Acid Anodizing: This is one of the most popular types of anodizing where machinists use chromic acid to create an anodizing layer over the aluminum part. Chromic acid is oxidizing acid, which is compatible with most types of aluminum alloys. An oxygen-producing anode is attached to the part being treated during the process. This part is then immersed to the electrolyte solution through which a current is passed. The current voltage is increased during the process to achieve the desired results. On passing the current, anode creates oxygen producing a layer of oxide film on the part. Chromic acid anodizing is employed for anodizing parts for aerospace applications. This process helps improve the part’s paint adhesion and corrosion resistance properties.
- Sulfuric Acid Anodizing: The sulfuring acid hard anodizing is similar to the chromic acid anodizing, however the key difference lies in the type of acid bath used. Sulfuric acid is oily and denser than chromic acid. The process’s current density and performance temperature also differ than chromic acid anodizing. This process is employed for creating colored parts.
- Hard Coat Anodizing/Bright Dip Anodizing: As the name suggests, this anodizing allows manufacturers to create parts with high luster. The process enables the operators to create harder and thicker coatings with a high current density and low temperature bath. This type of anodizing works the best for raw aluminum. Although brighter than the other two variants listed above, the parts can be dyed or not, as the client prefers, using this process.
An Overview of Anodizing Process Using Our Aluminum
The below-given process is generally followed when you use our anodizing process line.
- Anodizing starts with cleaning, where the material is cleaned to remove all impurities that may have accumulated during manufacturing or handling.
- The material is rinsed after the cleaning and then prepared for etching.
- In etching, a thin layer is etched on the material’s surface, which is to be anodized. The material is immersed in the acid or caustic etch bath containing fluoride. This fluoride produces a rough surface by forming a thin microscopic layer over the material. It helps conceal any imperfections such as small defects, minor corrosion, flow lines, and so on.
- In the next step, the material is deoxidized and, which prepares the surface for anodizing. The process of desmutting helps remove smut from the material surface. This smut is a mixture of metal, metal oxide, and intermetallics, which are basically residues formed due to chemical exposure in the etching process.
- Desmutted aluminum is immersed in an anodizing tank containing electrolytic solution. This makes it release hydrogen and oxygen. The hydrogen on reacting with the metal surface produces a cathode, a negative electron, and the oxygen on reaction produces anode, a positive electron. Due to these reactions, a layer of aluminum oxide is built upon the material’s surface. This leads to a finished surface of the metal.
- If required, the metal is colored in the next step. In this step, the electro-deposition of metal takes place to transform the aesthetic properties of the material.
- In the final step, anodized and colored aluminum is sealed using an elevated temperature hydrothermal seal and is given a hot water rinse.
Benefits of Aluminum Anodizing
Metal anodizing has emerged as one of the key surface finish options in recent years. The following properties of this process have contributed to its widespread popularity across industries.
- Durability: Anodizing produces an oxidized finish over the metal part and produces unmatched adhesion and strong bonding. This adds to the long lifespan of the part and helps reduce maintenance costs, and assures long-term savings.
- Ease of Maintenance: Many fabrication and surface finishing techniques and installation and handling may leave scars, wear and tear on aluminum parts. In such cases, these parts require frequent dirt cleaning and maintenance. But aluminum anodizing is a controlled process and leaves no scars on parts. The parts cannot be scratched easily and leave no fingerprints. Anodized parts can be cleaned upon accumulation of dirt and contaminants by rinsing with mild soap and water.
- Affordability: Low finishing costs with minimal maintenance costs make anodized coating affordable.
- Aesthetic Appeal: Anodizing lends gloss and color to aluminum parts and helps minimize color variations. Unlike other surface coating techniques, anodizing helps retain the metallic appearance.
- Color Stability: Anodic coating offers stability against harmful radiation and does not peel, chip, fade, and scratch easily, and needs no additional touch-up.
- Durable Parts: The process of anodizing creates a hard coating on the part. The oxidizing acid used during anodizing makes a hard coating and offers superior corrosion and abrasion protection.
- Improved Thermal Properties: The parts possess better thermal insulation properties than other coated parts.
- Health and Safety: The metal anodizing process is safe, involves no harmful chemicals, and produces no toxic chemicals. Also, the anodized part is chemically stable and does not decompose easily.
- Recyclable: Anodized aluminum parts are recyclable and pose no risk to the environment and users.
Common Applications of Anodized Finishes
Anodized finishing is common across industries. Our anodized process line are used to surface finish the following parts.
- Structures and architectural components including awnings, vents, dust covers, storm doors, light fixtures, window frames, bathroom accessories, mailboxes, and so on
- Motor vehicle components including control panels, trim parts, wheel covers, and name plates
- Leisure industry products including sporting goods, boats, golf carts, camping and fishing equipment
- Food preparation equipment including pans, display cases, grills, and coolers
- Commercial and residential building products including roofs, ceilings, curtain walls, escalators, floors, walls, staircases, and lobbies
- Computer hardware, scientific instruments, exhibit displays for tradeshows, and wide range of home appliances, building materials, and consumer products.
Aluminum anodizing is an essential surface finishing process in many industries. In other words, anodizing process line makes a significant investment for manufacturers who serve clients from aerospace, marine and other such industries. HPI Pro’s anodizing process line is designed keeping the anodizing requirements of our clients in mind. They are perfected over years of research and can be automated to meet the productivity and accuracy requirements in many manufacturing segments. If you have any questions or doubts regarding the efficiency of these systems, their operating modes, strengths, and so on, feel free to contact the HPI Pro’s team today. Having worked with several manufacturers over the years, the team clearly understands your requirements.