What is Anodizing & Anodization | Junying Custom Metal Finishing Services


In this guide, CNClathing.com will present a complete overview of the metal finishing method anodizing with definition, types, application, benefits, and more. Our aluminum anodizing service complies with ROHS standards. It is commonly used on machined aluminum parts to reduce corrosion and add an attractive metallic color to porous aluminum substrates. Anodizing helps to resist scratching, is a natural electrical insulator, and is one of the most durable finishes.

What is Anodizing & Anodization?

Anodizing (Anodising, Anodization) is an electrolytic passivation process of forming a thin layer of aluminum oxide on the exterior of aluminum CNC machined parts to increase the thickness of the natural oxide layer and protect the metal, as the layer has higher corrosion and abrasion resistance than aluminum. The metal part to be treated as the anode electrode. The oxide layer can be dyed in a diversity of colors, so it’s often used as a decorative finishing. Other than aluminum, nonferrous metals like magnesium and titanium can also be anodized.


Anodizing changes the microscopic texture of the surface and the crystal structure of the metal near the surface. Thick coatings are normally porous, so a sealing process is often needed to achieve corrosion resistance. Anodized aluminium surfaces, for example, are harder than aluminium but have low to moderate wear resistance that can be improved with increasing thickness or by applying suitable sealing substances. Anodic films are generally much stronger and more adherent than most types of paint and metal plating, but also more brittle. This makes them less likely to crack and peel from aging and wear, but more susceptible to cracking from thermal stress.

Sandblasting & silver anodized aluminum 6061 milling parts:

Types of Anodizing - Compare Different Anodization Processes

  • What is Type I Chromic acid Anodizing?
  • Type I, Chromic acid anodizing is a metal coating method that is utilized when a thin coating with a high degree of corrosion resistance is required. Type I coatings are created chemically by immersing an aluminum component in a chromic acid bath. Boric-Sulfuric Acid Anodize (BSAA) is a viable alternative to chromic acid anodize (CAA) owing to the environmental, worker safety, and health problems, as well as the associated expenses of continuing to employ hexavalent chromium-bearing procedures such as CAA. 


  • Benefits of Type I Chromic acid Anodizing:
  • – Excellent for products with strict tolerances: will not distort proportions 
  • – Can be painted black; other colors are impractical 
  • – Excellent for bonding 
  • – Non-conducting 
  • – Excellent for welded components and assemblies
  • What is Type II Sulfuric Acid Anodizing?
  • Type II, often known as “Color Anodize” or “Bright Dip,” is popular because of its lower cost and ability to produce an array of colors. Essentially, it is a “clear” anodize technique that allows for the addition of dye to create practically any hue. It gives a smooth, uniform surface and a reasonable amount of protection against mechanical damage and corrosion. Type II is appropriate for visually significant regions that get less wear. 
  • Benefits of Sulfuric Acid Anodizing:
  • – Less costly than other forms of Anodize in terms of chemicals utilized, heating, electricity consumption, and time necessary to achieve the desired thickness. 
  • – Additional alloys may be completed. 
  • – More resistant to corrosion than chromic anodize. 
  • – A more transparent finish enables a broader choice of colors to be dyed. 
  • – Waste treatment is less expensive than chromic anodizing.
  • What is Type III Hard Coat Anodizing?
  • Anodizing Type III (often referred to as MIL-A-8625 Type III in North America) is the same basic process as Type II and gives comparable advantages of enhanced resistance to wear, corrosion, and other general environmental impacts. However, this process is often referred to as hard or hard coat anodizing, since the protective oxide layer must be at least 0.001″ thick, with coats up to 0.004″ being applied occasionally. 
  • Benefits of Hard Coat Anodizing:
  • – Increased wear resistance 
  • – Non-conductive – Can be used to restore damaged aluminum surfaces 
  • – Increase the surface area of components for slide applications 
  • – May be colored black; other colors are less ornamental 
  • – Finish is more abrasion resistant than tool steel – Surface may be ground or lapped

What Machining Materials are Suitable for Anodizing?

Aluminum alloy is the primary material that uses anodizing process, which can also be applied to titanium and other metals.

– Aluminum 6061 & 6061-T6

– Aluminum 6063 & 6063-T6

– Aluminum 7075 & 7075-T651

– Titanium Grade 5 (6A1-4V)


Know about other CNC machining materials at Junying.

What Machining Processes Use Anodizing?

1. CNC Turning: a procedure in which a material block is clamped to a CNC turning center or lathe that is spinning rapidly, while the cutting tool moves into the rotating axis to process the workpiece, resulting in CNC turned pieces with precise dimensions. 

2. CNC Milling: Often referred to as the most popular machining method, this refers to the use of a CNC milling cutter to manufacture milled components with specific shapes and features in a stationery item, such as slots, holes, notches, and grooves. 

3. Rumbling & Tumbling: Similar to sanding, rumbling and tumbling both use abrasive media, however, the sanding particles in this instance are “loose” and unattached to any supporting paper. Numerous media may be employed depending on the workpiece and desired finish, including garnet, walnut shells, stones, or coarse sand. Tumbling involves the placement of components and abrasive particles in a box or tub, which is then rotated to mix everything together randomly. This is often used for “deburring,” or removing the sharp metal points left on the edge of a machined object after it has been machined. 

4. Magnetic Polishing: deep holes, pockets, and big inner chambers may sometimes need a high degree of polishing to provide a smooth surface with minimal frictional resistance to air or liquid. However, certain locations might be difficult or impossible to reach by hand, necessitating the use of a different approach. As with tumbling, metal components may be placed in a box or chamber containing magnetic particles. These particles may then be guided on the inside surface using a focussed magnetic field to create a fine polish. 

5. Sandblasting is a procedure that involves blasting a part’s surface with abrasive material at high pressure. Again, the kind of material utilized will dictate the final finish’s quality. Sandblasting, or blasting with a mixture of air and water, has the ability to swiftly cover a vast surface area. Additionally, shot-peening may enhance some of the mechanical qualities of metal by boosting fatigue strength and corrosion resistance. 

6. Lapping is a precise method used to achieve the maximum level of surface refinement and flatness. It is performed by a trained craftsperson using a soft iron tool and a mild abrasive slurry to work the surface gently with irregular, light, and non-linear movements. This fills tiny surface holes and reduces the height of high points.

Applications of Anodizing - Uses of Different Anodizing Process

Chromic acid anodizing: 

– Components optoelectronics 

– Components of medical devices 

– Body assemblies for hydraulic valves 

– Armed forces 

– Enclosures for computers and electrical devices 

– Accurately Machined Components 

– Components for Aerospace 

– Components and assemblies welded 

– As a basis for paint/primer 


Sulfuric acid anodizing: 

– Components optoelectronics 

– Body assemblies for hydraulic valves 

– Armed forces 

– Enclosures for computers and electrical devices 

– Mechanical components 


Hard coat anodizing: 

– Valves 

– Pistons 

– Sliding Components 

– Hinges 

– Cams 

– Gears 

– Swivel Joints 

– Insulation Plates

Benefits of Anodization/Anodizing

1.  Improved properties. The corrosion and abrasion resistance of metal parts are enhanced.

2.  Long-lasting. As the anodized surface is porous, it’s easy to absorb and retain the color.

3.  High strength. The anodized aluminum parts are harder than non-treated aluminum.

4.  Wear resistance. The anodizing increases the thickness of the protective film, making the metal are more durable and wear-resistant.

5.  Good-looking appearance. Black, red, yellow, green, blue, orange, various colors can be chosen to get the desired look.

For questions or more information about our anodizing service and custom coatings, or to start selecting the right finish for your project, please Contact Us immediately.