Hard Anodized Aluminum - Aluminum Anodizing Service- Sunrise Metal

Why You Would Use Hard Anodized Aluminum

Due to its properties such as non-conductivity and lightweight, aluminum is used as an alternative to steel in construction and manufacturing. Most of these applications need a stronger metal. Hence, aluminum is anodized to make it’s surface stronger.

The process of anodizing involves immersing the aluminum metal in a pool of sulfuric acid and then passing an electric current. A chemical reaction takes place and a coating of aluminum oxide forms on the metal. When the acidic solution is cooled to the freezing point and the electric current increased, the process is known as hard anodizing.

The good thing about hard-anodized aluminum is its lower overall weight and cost. Moreover, it is easier to machine hard anodized aluminum. The process produces products that are resistant to abrasive machining, salt sprays, and harsh weather.

Hard Anodizing Aluminum Process

Usually, you will need to hang the aluminum part on a rack to ensure there is an electrical contact. At any given stage of anodizing, the aluminum parts are affixed to racks that are suspended in a tank.

Dipped: The aluminum part is then dipped in a tank that contains a cleaning agent to get rid of surface dirt. You need to rinse the part to prevent contamination with the solutions in subsequent tanks.

De-oxidized: After this, the aluminum part is de-oxidized with the help of acid. In most cases, sulfuric acid is used. It helps get rid of the non-uniform oxide layer. Then, you should rinse the part to prevent contamination.

hard anodizing processEtching: Another process that is necessary during anodizing is etching. This process eliminates natural shine and offers a textured, soft appearance.

Your aluminum part should be suspended in a tank that contains a water and acid mixture that allows electric current flow. In this case, the temperature, acid used, and amount of voltage are critical parameters that have an impact on the desired color and finish.

The amount of electric current supplied varies depending on the size to be coated. Also, the electrolyte solution must be agitated to offer a solution with uniform temperature. Usually, the process takes about one hour to complete.

If you want to add color or dye, you should dip the part in a tank with organic dye, which should be water-soluble and diluted. The duration and temperature vary depending on the dye used.

Sealing: The last step of hard anodizing is sealing the dyed outer layer from staining or being bleached by the sunlight. The sealed outer surface has higher corrosion resistance.

Hard Anodizing Parameters

You should note that hard-anodized aluminum parameters have an impact on the properties of the oxide produced. When using acidic concentrations and low temperatures, it has a harder and less porous coating. The acidic content, high temperature, and longer immersion duration produce more porous, softer coatings.

Even minor changes to the aluminum part or any parameter can have a considerable impact on the coating. Through different measurement techniques and process controls, it is possible to monitor, correct, and control the process.

You should note that thickness is the critical quality control measure. It is possible to measure the thickness by using non-destructive methods. In this way, you can ensure that anodizing occurs across the surface.

Differences between Hard Anodizing and Regular Anodizing

Appearance and Thickness

The primary difference between hard-anodized aluminum and anodized aluminum is thickness. Ideally, the hard-anodized one is thicker as compared to the regular anodized one. Thus, the hard-anodized aluminum has a surface with higher abrasion resistance. Moreover, it has a uniform surface.


Regular anodizing can use electrolytes such as sulfuric acid or chromic acid. However, hard anodizing is done with a solution that is a mixture of sulfuric acid and oxalic acid.

Production Conditions

The hard anodizing coating can only be produced when the temperature is lower and a high electric current.

hard anodized aluminum parts


Aluminum Products with hard-anodized are applicable in environments and applications that need wear-resistant, heavy-duty surfaces. Thus, the applications are for making pistons, cookware, hydraulics, and even buildings. Standard anodized aluminum parts and products exist in the aerospace, automotive, and architecture industries.

Hard Anodized Aluminum Benefits

Hard anodizing is one of the most desirable and effective methods of finishing die-cast aluminum. These are the primary benefits of hard anodizing aluminum:

Excellent Durability

Hard anodized aluminum does not experience wear as a result of installation, maintenance, usage, and handling.


Hard anodized aluminum parts maintain excellent color stability whenever they are exposed to the UV rays. The coating cannot be peeled or chipped and has a great coloring process.


You only need water and mild soap to restore the hard-anodized part to its original appearance.


You should note that hard anodizing aluminum is more cost-effective than other finishing techniques. Also, with its low maintenance costs and excellent durability, it minimizes the replacement costs.


It provides a range of color and gloss alternatives. Also, it maintains the metallic appearance of the aluminum.


Hard anodizing of aluminum is an environmentally-friendly process and does not cause harm to humans. Remember that the anodized finish is stable, non-toxic, and does not decompose. The fact that the anodizing process reinforces the oxide process, does not result in hazardous by-products.

Hard Anodized Aluminum Applications

hard anodized aluminum components

Hard anodized aluminum provides excellent durability and ease of maintenance. As a result, it is used for a range of applications. In fact, these are some of the industries that use hard-anodized aluminum parts:

  • Aerospace
  • Food manufacturing
  • Construction
  • Military
  • Marine industry
  • General manufacturing
  • Electronics

Sunrise Metal Hard Anodizing Service

Sunrise Metal offers hard anodizing service for aluminum die casting. You can be assured of finishes that offer an easy to maintain surface, flame resistance, improved abrasion resistance, and durability.

Sunrise Metal is IATF 16949 and ISO 9001 certified. Thus, you can expect high quality hard anodizing aluminum parts.

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