Benefits of Chromic Acid Anodization

  • An icon of a line going over a surface.

    Creates a very thin coating of 0.05 to 0.2 mils (0.0001 cm to 0.0005 cm).

  • An icon of a flexing arm with an anchor tattoo.

    Has minimal impact on fatigue strength of components.

  • An icon of a shield.

    Coating offers excellent corrosion resistance.

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Chromic Acid Anodization Process Details

This process involves a chromic acid bath and increasing the applied voltage by 5 - 7V per minute starting from about 5V and going up to 40V through specific steps throughout the process. This anodization process is common on precision machine components and metalworking components for the aerospace industry, including welded components and assemblies. The anodization layer can be dyed — though it is more difficult than with Type II — and this process can also be used as a pretreatment before painting.


Featured Solution — 3M™ Anodization Masking Tape 8985L

  • A metal ring fastener.

    VIEW PRODUCT DETAILS

  • A purple circle.

    Clear purple polyester backing allows for easy accurate positioning while resisting abrasion, tears, scratches and punctures.

  • A roll of transparent, purple tape.

    Non-silicone rubber adhesive removes cleanly in one piece while providing sharp masking lines and without interfering with downstream painting processes.

  • A worker preparing materials to be anodized.

    Can speed up masking and de-masking process by up to 5 times while helping reduce labour time and associated costs by up to 60%.*

    *3M internal data on file.

Benefits of “Regular” Sulfuric Acid Anodization

  • An icon of a thermometer.

    Can be done at room temperature with 10V to 20V.

  • An icon of a mallet.

    Provides a harder finish than chromic acid anodization.

  • An icon of a hand with two coins falling into it.

    Inexpensive compared to other processes.

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“Regular” Sulfuric Acid Anodization Process Details

Although Type II anodization may use other acids, sulfuric acid is the most commonly used. Producing a layer 0.1 to 0.8 mils thick, Type II anodization is performed at room temperature using approximately 10 - 20V and provides a harder finish than Type I. Type II anodization is most commonly used for military-grade components, shells for computers and other electronics, hydraulic valve bodies and mechanical hardware.


Featured Solutions

  • A roll of shiny black tape.

    3M™ Polyester Tapes

    • Silicon adhesive
    • 3.2 mils (0.008 cm) thickness
    • Lead product choice
  • A roll of shiny grey tape.

    3M™ Lead Foil Tapes

    • Rubber adhesive
    • 5.2 mils (0.13 mm) thickness
    • Non-silicone
    • Conformable
  • A roll of blue tape.

    3M™ Vinyl Tape 471

    • Rubber adhesive
    • 5.2 mils (0.13 mm) thickness
    • Non-silicone
    • Conformable
  • A roll of shiny silver tape.

    3M™ Aluminum Foil Tape 425

    • Acrylic adhesive
    • 4.6 mils (0.12 mm) thickness
    • Non-silicone
    • Conformable

Benefits of “Hardcoat” Sulfuric Acid Anodization

  • An icon of a line going over a surface.

    Creates a “hardcoat” finish up to 2 mils thick (0.005 cm).

  • An icon of a shield.

    Provides electrical and thermal insulation properties.

  • An icon of a hammer and an anvil.

    Extremely resistant to wear and corrosion.

An icon of a lightbulb.

“Hardcoat” Sulfuric Acid Anodization Process Details

Similar to Type II anodization, Type III is most commonly done with sulfuric acid, although other acids, or even combinations of acids can be used. Type III anodization is more complicated than Type I or Type II, and requires very cold conditions and up to 90V. Type III anodization is most commonly used for internal engine parts, sliding parts, hinge mechanisms and blast shields.


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Featured Solutions

  • A roll of shiny black tape.

    3M™ Polyester Tapes

    • Silicon adhesive
    • 3.2 mils (0.008 cm) thickness
    • Lead product choice
  • A roll of shiny grey tape.

    3M™ Lead Foil Tapes

    • Rubber adhesive
    • 5.2 mils (0.13 mm) thickness
    • Non-silicone
    • Conformable
  • A roll of blue tape.

    3M™ Vinyl Tape 471

    • Rubber adhesive
    • 5.2 mils (0.13 mm) thickness
    • Non-silicone
    • Conformable
  • A roll of shiny silver tape.

    3M™ Aluminum Foil Tape 425

    • Acrylic adhesive
    • 4.6 mils (0.12 mm) thickness
    • Non-silicone
    • Conformable
An anodizing machine in a factory.

3M™ Extreme Masking Tapes for Anodizing

Anodization baths are some of the toughest environments around and we make extreme masking tapes tough enough to stand up to them.

ASK AN EXPERT

Unlike paint which bonds to metal surfaces but remains a separate coating, anodization converts the surface to provide a durable, corrosion-resistant oxide finish that is both part of the metal itself but also different from it. The finish is achieved by applying an electric current while dipping parts in an acid bath — so any section that shouldn’t be treated needs a tough masking tape for anodizing that can withstand this process.


Benefits of Anodization

  • An icon of a mallet.

    Hard, abrasion-resistant surfaces will not peel or crack.

  • An icon of a shield with a lightning bolt on it.

    Electrically insulates the underlying metal.

  • An icon of a stack of squares with a line through it.

    Avoids thickness of painting and plating processes.

  • An icon of a paint swatch.

    Colour can be embedded for decorative purposes.


The Three Common Anodizing Processes

Type I

Chromic Acid Anodizing toggle

Type II

“Regular” Sulfuric Acid Anodizing toggle

Type III

“Hardcoat” Sulfuric Acid Anodizing toggle


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Related Applications

  • Image of a worker in protective gear preparing to hang a rack of parts in an electroplating bath.

    Electroplating

    Use electricity to deposit a layer of any desired metal on another substrate in order to change the surface properties or to build up part thickness. Your masking tape must withstand the immersive solution without leaking but should also remove easily and cleanly with no or minimal residue requiring further attention.

  • Image of a worker in protective gear applying powder coat paint to metal parts.

    Powder Coating

    Use electrical attraction to apply free-flowing dry powder to a part which then passes through an oven that melts the powder to form an even paint surface. The masking tape must be able to prevent powder from reaching masked areas while withstanding the high oven heat without transferring to the part completely.