Sulfuric Acid Anodizing
MIL-A-8625 Type II — Class 1&2
*** Class 1 Non Dyed — Clear
*** Class 2 Dyed — Black, Red, Blue, Gold, Green, & Yellow Anodize
All of our anodizing and color dyes are also RoHS compliant.

Chemical Conversion Coating on Aluminum and Aluminum Alloys
MIL-C-5541 — Hexavalent Type

*** Class 1A For maximum protection against corrosion, for surfaces to be painted or left unpainted.
*** Class 3 For protection against corrosion where higher electrical conductivity is required.

RoHS Clear Chromate (Restriction of Hazardous Substances)
This specification standard was developed in Europe and has been fully adopted by all concerned US businesses.
** Our RoHS Chromate conforms to US military requirements and is presently being used by the US Government.
** It Covers: MIL-DTL-81706B Type II
MIL-DTL-5541 F Type II

Citric Acid Passivation (RoHS Compliant)
++ This is the latest development in the art of passivating stainless steel.
++ Environmental and worker friendly
++ No dangerous nitric acid
++ Non fuming, safe without a respirator
++ No waste treatment necessary
** It Covers: ASTM-A967-Method II
ASTM-A380-Method II

Circle Finishing also offers the following surface treatments:
++ 1000 Glass Bead Blasting
++ Metal Polishing-All types

We are a small quantity waste generator and do not discharge any waste stream to the municipal treatment plant.
** Our system is "Closed loop", recycling our water where ever
possible. The remaining water is concentrated and manifested
off site for documented treatment or reclamation.
** There is no environmental threat to our customers.

** We also offer electroplating and electroless metal finishes through
our associate company Circle Polishing, Inc. which was founded in 1997 by Rod L’Italien.

++ Gold, Silver, Copper, Nickel, Chrome, Tin & Zinc

Circle Finishing is located at 19 Graf Road, Newburyport, MA and can be reached at 978.465.6136. We offer polishing & buffing of all metal surfaces and custom plating.

Description of Our Services

Anodizing, Plating, & Other Finishing

Circle Finishing is your single source for metal finishing requirements for aluminum, metal plating, and other metal finishing services. We are equipped to handle a variety of other specific metal finishing requirements, including Sulfuric Anodizing and other specified metal finishing techniques.

What is Type II Anodizing

Type II Anodizing is most commonly based off the military specification MIL-A-8625. This is the standard specification used around for the world for commercially anodized aluminum in the medical, aerospace, and automotive industries as well as for military and defense applications. It is an electrochemical process done in a sulfuric acid bath to speed the natural oxidation of the aluminum alloy. This provides an oxide layer with improved wear resistance, hardness, and corrosion resistance.

Benefits of Type II Anodizing

There are many benefits of Type II Anodizing. A sealed anodized part is stain resistant, easy to clean, and is heat resistant up to the melting temperature of the aluminum itself. The process can be applied to all alloys of aluminum. The process gives the aluminum improved paint adhesion as well as providing good electrical insulation. The corrosion resistance that it provides is excellent for all applications including marine, industrial, high humidity, and even outer space. The part is able to withstand a minimum of 336 hours of 5% salt spray testing per ASTM B 117. The part can be bright dipped as well to produce an appearance that is much brighter and has more reflectivity than the raw part itself.

Dyeing of Type II Anodizing

A big feature of Type II Anodizing is the ability to dye the part to a variety of different colors. These can include black, blue, purple, yellow, red, green, gray, orange, and any number of combinations of different colors. This dyeing is useful for part identification, inventory control, and pure aesthetics. Most colors are light fast and can withstand very bright or hot environments without degradation of the color.

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