Anodizing
Anodizing is an electrochemical conversion process that forms an oxide film, usually on aluminium, in an electrolyte (chemical solution). The aluminium parts are the anode (thus the term “anodizing”) and current is passed between them and a cathode, usually flat aluminium bars, through the above mentioned electrolyte (sulphuric acid is most commonly used). There are different types of anodize, most commonly referred to as Type I-Chromic Acid Anodize, Type II-Sulphuric Acid Anodize, and Type III Hard Anodize or Hard coat from the Mil-A-8625 designation. Other less common types are phosphoric acid and titanium anodize. The anodize is a porous structure that grows out of the base aluminium and absorbs coloured dye very well. This is done through a secondary operation with either an organic or inorganic colouring. Manideep processes black, blue, red, gold, as well as small lots of green and gray using standard organic dyes. We also do electrolytic colouring which produces a gray-black colour using inorganic metallic salts. Any coloured anodize is required to be sealed following processing in order to preserve the colour.
Chromic Acid Anodize
Chromic Acid Anodize
- Good for tight tolerance parts: will not change dimensions
- Can be black dyed – other colours not practical
- Good for Bonding
- Non-Conductive
- Good for welded parts and assemblies
Chromic Acid Anodize Applications:
- Precision Machined Components
- Aerospace Components
- Welded components and assemblies
- As a paint/prime base
Boric-Sulfuric Acid Anodize (BSAA)
Boric-Sulphuric Acid Anodize (BSAA) is an alternative to chromic acid anodize (CAA) due to the environmental, worker safety and health concerns and the related costs associated with continued use of hexavalent chromium-bearing processes such as CAA. Primary applications include aircraft and aerospace components. It is covered by MIL-A-8625, Type I c and aerospace specifications including Boeing’s BAC 5632. It is used for corrosion protection and paint adhesion. Paint adhesion is equal or superior to chromic acid, and the process is more energy-efficient than chrome-based processes.
Boric-Sulphuric Acid Anodize Features:
- Good for tight tolerance parts: will not change dimensions
- Corrosion protection
- Good for Bonding
- Non-Conductive
Boric-Sulfuric Acid Anodize Applications:
- Precision Machined Components
- Aerospace/Aircraft Components
- As a paint/prime base
Sulfuric Acid Anodize
Sulphuric Acid Anodize Benefits:
- Less expensive than other types of Anodize with respect to chemicals used, heating, power consumption, and length of time to obtain required thickness.
- More alloys can be finished.
- Harder than chromic anodize.
- Clearer finish permits dying with a greater variety of colours.
- Waste Treatment is easier than chromic anodize, which also helps to reduce cost.
Sulfuric Acid Anodize Applications:
- Optical components
- Hydraulic valve bodies
- Military weapons
- Computer and electronic enclosures
- Mechanical hardware
Hard Anodize (Hard Coat)
Hard Anodize Features:
- Improved wear resistance
- Non-conductive
- Can repair worn surfaces on aluminium
- Improve parts surface for slide applications
- Can be black dyed; other colours less decorative
- Finish is harder than tool steel
- Can be ground or lapped
Hard Anodize Applications:
- Valves
- Pistons
- Sliding Parts
- Hinge Mechanisms
- Cams
- Gears
- Swivel Joints
- Insulation Plates
- Blast Shields