METAL FINISHING EQUIPMENT

CHEMICAL SOLUTIONS

product data

 

Anodizing

Aluminum anodizing is an electrochemical process that produces a porus aluminum oxide surface.  The aluminum oxide produced provides excellent durability and wear resistance, electrical insulation, increased corrosion resistance and the ability to accept colored dyes.   The thickness of the aluminum oxide coating is controlled by a precise combination of chemical concentration, temperature, process time and current density. 

There are three main types of aluminum anodizing and each use unique solution parameters to achieve specific performance characteristics.  Type 1 anodizing uses chromic acid as the electrolyte to build the anodic coating.  Type 2 anodizing uses sulfuric acid at a temperature range of (70 – 85°F) to build the anodic coating and Type 3 uses sulfuric at a temperature range of (25 – 35°F) to achieve a  “Hard Coat” deposit.   

  1. Cleaning aluminum can be accomplished using neutral, alkaline or acidic based chemistries.  One of these cleaning technologies will be recommended depending on the alloy and the oils or soils on the metal surface. 
  2. Rinsing: Multiple or counterflow rinses, some using strictly de-ionized water, follow each process step.  Rinsing is critical to preventing contamination of subsequent process tanks.  Rinse tank controllers and conductivity meters can be used to help maintain optimum cleanliness in rinse tanks.
  3. Etching (Chemical Milling): Etching in caustic soda (sodium hydroxide) prepares the aluminum for anodizing by chemically removing a thin layer of aluminum. This alkaline bath gives the aluminum surface a matte appearance.  Acidic etches are also available.
  4. Desmutting: Rinsing in an acidic solution removes unwanted surface alloy particles.  Desmutting can be accomplished using commodity acids or proprietary iron based chemistries.   
  5. Anodizing: Type I (chromic acid), Type II (conventional), Type III (hard coat).  Proprietary anodizing additives can be used in the solution to help open up the current density and temperature operating window.  Stretching these parameters can help reduce rejects, improve production and increase profitability.    
  6. Coloring: Porus anodic films are well suited to accept coloring methods including absorptive dyeing, both organic and inorganic dyestuffs, and electrolytic coloring.  New advancements in manufacturing have increased the purity and performance of many dyes.  
  7. Sealing: During sealing the porosity is greatly decreased while the corrosion resistance is enhanced.  The two main proprietary chemistries used to seal anodized aluminum are based on nickel acetate and nickel fluoride platforms.  Nickel acetate based systems typically operate at higher temperatures up to 190° F, while the nickel fluoride seals operate at “room temperature” or around 80° F.  There are advantages and disadvantages for both systems.

 

JSA works with chemical manufacturers that research and develop the highest performing products that will maximize the production capabilities of your anodizing line.  Please click here to fill out a form that will help us learn about your application and allow us to promptly and accurately respond to your needs.  Thank you.