Anodizing and Coloring Process
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
Increased corrosion resistance .
Increased durability / wear resistance .
Ability to be colored through dying and
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
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
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
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