Aluminum Anodizing

Standard Sulfuric, Bright Dip Color,
Chromic Acid, Hard Coat



Anodizing successfully combines science with nature to create one of the world’s best metal finishes. Developed over 50 years ago, anodizing is an electrochemical process that forms a protective coating of aluminum oxide on the surface of the aluminum. Raw aluminum left exposed will corrode and oxidize, creating weakness and becoming unsightly. Anodizing protects the raw aluminum, transforming it into a hard and durable, weather-resistant substance. Anodized coatings can be colored by dyeing – and because anodizing is a chemical bond to the metal, these colored coatings cannot flake or peel. The microscopic structure of an anodized coating consists of many small hexagonal pores. These are filled with a sealer that hydrolyzes the pores to create a smooth, durable surface.

Bright Dip Anodizing – the ultimate look in anodizing:
Bright dip is an especially brilliant finish achieved by using the bright dipping process. Bright dip’s attractive gloss finish helps accent colors as well as graphics and lettering. Pilkington offers bright dip anodizing in a variety of colors.

Hard Coat Anodizing – for maximum durability:
Hardcoating results in a protective finish that is up to 8 times thicker and 10 times more durable than standard anodizing. Other properties of hardcoating include: super long life span, resistance to outdoor conditions, exceptionally hard surface, easily cleaned and heat resistant. Hard coating has applications in industries where components require wear-resistant surfaces – for example, cylinders, hydraulic gears, and machine molds.

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Our Process

We consistently follow the same documented process to obtain a truly high-quality and long-lasting anodize finish. Many steps are involved, including the following:

Cleaning – At Pilkington, your product is cleaned using ultrasonic vapor degreasing, acid wash, and/or alkaline cleaning.

Mechanical and Chemical Pre-Treatments – After cleaning, your product is pre-treated to achieve the desired degree of reflectivity. Three of the chemical pre-treatments we offer are bright dip (highly reflective, gloss-like finish), satin (low lustre – the most common finish), and matte (flat finish).

Treatment – This is the step where your product is actually anodized. Your anodizing options include standard sulfuric anodizing and hardcoat anodizing. We use approved and particular specifications to finish your products. See our complete list of specifications.

Finish – In the last step of the anodizing process, the final finish is achieved through application of color dye and sealants.

Durability – Anodizing results in a complete bonding of the finish coating and the aluminum – so the finish cannot peel off because it is actually part of the metal. An anodized finish is chemically stable and heat resistant to the melting point of aluminum, which occurs around 1,221 degrees F.

Cost – Due to their extremely long life span, most anodized products offer significant economic advantages.

Color Stability and Selection – Anodizing gives aluminum a deep, rich metallic sheen. The anodized coating is translucent, which is why the aluminum retains its metallic appearance after it is anodized. Exterior anodized color coatings do not chip or peel and are resistant to ultraviolet rays.

Size Capabilities

Process Tank Size Nadcap Certified
Sulfuric Acid Anodize 14′ × 6′ × 4′ Yes
Hard Coat Anodize 7′ × 4′ × 3′ Yes
Bright Dip Anodize 3′ × 3′ × 3′ No
Boric Acid Anodize 7′ × 4′ × 3′ Yes
Chromic Acid Anodize 7′ × 4′ × 3′ Yes

Applicable Specifications

Specification Title Customer
AMS2469 Hard Anodic Coating on Aluminum and Aluminum Alloys Industry Standard
AMS2471 Anodic Treatment of Aluminum Alloys Sulfuric Acid Process, Undyed Coating Industry Standard
AAMA611 Voluntary Specification for Anodized Architectural Aluminum Boeing
ASTM B117 Standard Practice for Operating Salt Spray (Fog) Apparatus Industry Standard
BAC5022 Sulfuric Acid Anodic Films Boeing
BAC5632 Boric Acid – Sulfuric Acid Anodizing Boeing
BAC5821 Hard Anodizing Boeing
DPS9.314 Polishing & Texturing Aluminum Surfaces Boeing
DPS11.04 Hard Anodizing Aluminum Boeing
DPS11.05 Sulfuric Acid Anodizing Boeing
MIL-A-8625 Type I Chromic Acid Anodizing, conventional coatings produced from chromic acid bath Industry Standard
MIL-A-8625 Type IC Non-Chromic Acid Anodizing, for use as a non-chromate alternative for Type I and IB coatings Industry Standard
MIL-A-8625 Type II Sulfuric Acid Anodizing, conventional coatings produced from sulfuric acid bath Industry Standard
MIL-A-8625 Type IIB Thin Sulfuric Acid Anodizing, for use as a non-chromate alternative for Type I and IB coatings Industry Standard
MIL-A-8625 Type III Hard Anodic Coatings Industry Standard
P3100 Coatings per P3101 or P3102 optional – Anodic Coating for Aluminum and Aluminum Alloys Williams Intl.
P3102 Conventional Coating produced from a Chromic Acid Bath – Anodic Coating for Aluminum and Aluminum Alloys Williams Intl.
P3103 Hard Coating – Anodic Coating for Aluminum and Aluminum Alloys Williams Intl.