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Surface finishes

Aluminum anodizing Services

The Type II and Type III anodization processes are the main services. These techniques confer optimal and various surface finishes tailored for aluminum components. Anodization serves to fortify the structural integrity of aluminum parts and is offered in a diverse colors.

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Aluminum Anodizing Servcie

Various anodization primarily recognized as Type I-Chromic Acid Anodize, Type II-Sulfuric Acid Anodize, and Type III Hard Anodize or Hardcoat from the Mil-A-8625 specification. Less prevalent alternatives encompass phosphoric acid anodize and titanium anodize. Anodization engenders a porous matrix that develops atop the foundational aluminum substrate, facilitating substantial absorption of pigmented dyes.
  • Sulfuric Acid Anodize:

    The sulfuric acid process is the most common method for anodizing. The sulfuric acid anodize process films range from .0001"-.001" thick. The overall thickness of the coating formed is 67 percent penetration in the substrate and 33 percent growth over the original dimension of the part. It is particularly suited for applications where hardness and resistance to abrasion is required.

    The porous aluminum oxide absorbs dyes well, and subsequent sealing helps to prevent color loss in service. Although dyed anodized films are reasonably colorfast, they have a tendency to bleach under prolonged direct sunlight.

    Some of the colors are: Black, Red, Blue, Green, Urban Grey, Coyote Brown, and Gold. Parts can be treated chemically or mechanically prior to anodizing to achieve a matte (non-reflective) finish.

    Consistency Requirements

    • Less expensive than other types of Anodize with respect to chemicals used, heating, power consumption, and length of time to obtain the required thickness.
    • More alloys can be finished.
    • Harder than chromic anodize.
    • Clearer finish permits dying with a greater variety of colors.
    • Waste Treatment is easier than chromic anodize, which also helps to reduce cost.

    Sulfuric Acid Anodize Applications:

    • Optical components
    • Military weapons
    • Mechanical hardware
    • Hydraulic valve bodies
    • Computer and electronic enclosures
  • Hard Anodize (Hardcoat):

    Hardcoat anodize, while usually done in a sulfuric acid based electrolyte, is much thicker and denser than the more conventional sulfuric anodize. Hardcoat is specified for aluminum components subject to extreme wear applications where superior abrasion resistance is needed, or corrosive environments where a thicker, harder, more durable coating is necessary.

    It can also be valuable where enhanced electrical insulation is required. Since hardcoat anodize can be built up to several thousandths in some cases, it makes this type of anodize a candidate for salvaging worn or mis-machined components.

    Consistency Requirements

    • Improved wear resistance
    • Non-conductive
    • Improve parts surface for slide applications
    • Can repair worn surfaces on aluminum
    • Can be black dyed; other colors less decorative
    • Finish is harder than tool steel
    • Can be ground or lapped

    Sulfuric Acid Anodize Applications:

    • Valves
    • Pistons
    • Sliding Parts
    • Sliding Parts
    • Insulation Plates
    • Hinge Mechanisms
    • Cams
    • Gears
    • Gears
    • Blast Shields

Color options for aluminum anodizing

The color of anodized finishes may exhibit some degree of variation due to standard alloy tolerance differences. Please refer to the color scheme below to observe the range of available colors.* We supply a range of standard colors (see Color options). If you need a particular RAL or Pantone color code, please contact

Black (Black MLW)

Similar to: RAL 9004, Pantone Black 6


Similar to: depends on material

Red (Red ML)

Similar to: RAL 3031, Pantone 1805

Blue (Blue 2LW)

Similar to: RAL 5015, Pantone 3015

Orange (Orange RL)

Similar to: RAL 1037, Pantone 715

Gold (Gold 4N)

Similar to: RAL 1012, Pantone 612

All colored surface treatments (anodizing/powder spraying/painting, etc.) will have color difference, which is reflected in several aspects: 1. Different product sizes, even if the material is the same and the color is the same, there will be color difference, the aluminum box There will be color difference between the body and the cover 2. There will be color difference between different batches, because the oxidation time and coloring effect cannot be guaranteed to be exactly the same 3. If the same color is anodized without using different grades of the same material, there will be color difference 4. Different surface treatment types will have color difference, such as anodizing and powder spraying, if you choose the same Pantone color card number, there will also be color difference

Color options for aluminum anodizing

TypeImpracticable situationFeaturesThickness(μm)ApplicationColorsPIC
Chromic acid (Type |)a.Aluminum alloy parts with copper content > 5%
b.Aluminum alloy parts with copper and silicon content > 7.5%
maintains the accuracy and surface roughness of original parts ,well bonding preformance3μma.1. Lap, riveted, welded or complex shaped parts
b. Parts with high precision and low roughness
black,other color is imparctical
Sulfuric acid (Type II )Lap, spot weld or riveted partthe most common type of anodizing,can dye with a greater variety of colors0.5~20μmThe part that need brighten appearance or special color, as decoration or identification mark.Black, Red, Blue, Green, Coyote Brown, Urban Grey, and Gold,allow for practically any hue
Hard Anodize (Type 1I)Parts with high fatigue performance requirementssuperior abrasion performance and electrical insulation,HV>42030~120umvalves/hinges/cams/gear/insulation platesblack,other colors are less ornamental
Organic acid (Type IC)uneven and amorphous black regions develop.Anodizing can produce yellowish integral colours without dyes if it is carried out in weak acids with high voltages, high current densities, and strong refrigeration.upto50umIntegral colour anodizingpale yellow, gold, deep bronze, brown, grey, and black
Tolerance for all surface preparation are held after anodizing.

Gallery of anodized parts manufactured by LML

The color of anodized finishes may exhibit some degree of variation due to standard alloy tolerance differences. Please refer to the color scheme below to observe the range of available colors.* We supply a range of standard colors (see Color options). If you need a particular RAL or Pantone color code, please contact




Heat Treatment



Example of a bead blasted part

Aluminum Anodizing Process By Lml

The aluminum anodizing process involves sequential steps for improving surface properties and appearance.

  • * Degreasing: Aluminum is cleaned to remove dirt and contaminants.
  • * Rinse: Cleaned aluminum is rinsed to eliminate residual agents.
  • * Polishing: Chemical or electrochemical polishing smoothens imperfections.
  • * Anodizing: Aluminum is immersed with a cathode in an electrolytic solution. Electric current

causes controlled oxidation, forming a substantial aluminum oxide layer.

  • * Activation: The surface is activated for effective dye absorption.
  • * Dyeing: Pigments or dyes enter aluminum oxide pores, adding color options.
  • * Sealing: Immersion in a sealing solution closes pores, enhancing durability and corrosion resistance.

Design Considerations for Aluminum Anodizing:

* Fixture Placement: During anodizing, components are suspended using a "jig" or "rack," which can result in marks where anodizing is not feasible. To prevent this, identify critical areas on your part where such marks are unacceptable.

* Electrical Insulation: Anodizing creates an insulating layer on your parts, impacting their conductivity. Factor in this change when designing components that require specific electrical properties.

* Masking Evaluation: Anodizing typically doesn't significantly alter the thickness of your part. So masking is usually unnecessary. However, if you wish to protect certain areas from anodization, clearly indicate these regions in your CAD file.

* Type III Anodizing: For Type III anodizing, which involves a thicker coating, consider masking or plugging threaded holes, reamed holes, and surfaces critical to your component's functionality. This precaution ensures that the added thickness doesn't interfere with the intended fit and function.

* Heat Dissipation: Anodizing affects thermal conductivity. Evaluate whether anodized surfaces might impact the component's heat dissipation properties.

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