Anodizing and Coloring Process

       Aluminum anodizing is the electrochemical process by which aluminum is converted into aluminum oxide on the surface of a part. This coating is desirable in specific applications due to the following properties:

  • Increased corrosion resistance .

  • Increased durability / wear resistance .

  • Ability to be colored through dying and Electro coloring.

The Process Principle :

The process of anodizing is rather simple. It consists of an anodizing solution typically made up of sulfuric acid. A cathode is connected to the negative terminal of a voltage source and placed in the solution. An aluminum component is connected to the positive terminal of the voltage source and also place in the solution. When the circuit is turned on the oxygen in the anodizing solution will be liberated from the water molecules and combine with the aluminum on the part forming an aluminum oxide coating.

Types of Anodizing:

Over the last several decades a variety of anodizing processes have been developed. However, there have been three main variations of aluminum anodizing: chromic anodizing, sulfuric anodizing, and hard  anodizing. Each of these has advantages and disadvantages depending on the application.

Chromic Anodizing:
Utilizing a chromic acid electrolyte this form of anodizing yields the thinnest coatings, only .05 to .1 mils thick. Chromic anodizing is a good choice when a part is complex and difficult to rinse because chromic acid is less corrosive than sulfuric acid used in other anodizing methods. Chromic anodize also reduces the fatigue strength of the aluminum less than the other methods described.

Sulfuric Anodizing:
This form of anodizing yields coatings under 1 mil thick. Although it offers mild abrasion resistance it is more durable than chromic anodize. Like most anodizes corrosion resistance is excellent. The most desirable feature of this form of anodizing would be the excellent results from dyeing yielding deep and rich colors.

Hard Anodizing:
Sulfuric Hard anodize is formed by using an electrolytic solution of sulfuric acid at a lower temperature and it has higher wear resistance. This will produce a Rockwell C-scale rating of 60-70. This is an excellent coating for many wear situations.

Electrocolouring and Dying:
After anodizing different coloring finish can be given by Electrocoluring and Immersion in organic dye solutions. This is possible because the anodize coating has microscopic pores that, depending on variables already described, allow aluminum to absorb dyes through immersion. Typically, the darker the color desired, the longer the anodize time is required. For details of electrocolouring and dying process please contact us.
                      We supply complete chemicals and equipments required for anodizing, dying and electrocolouring. We give consultancy and supply DC Rectifiers, Tanks, Cooling plant, chemicals, dyes, elctrocolouring chemicals, AC rectifiers for electrocolouring.

 If you want to start an anodizing and electrocoluring unit  contact us

 

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