A look into the anodisation process

Anodisation Process

As an OEM/custom machined metal parts manufacturer, Unison Tek is not just experienced in the turning and milling process, but also have had affiliated companies who can take care of different surface treatments for us – anodisation, for example, is a process that’s being heavily used on our machined parts.

What is anodisation?

Anodizing is an electrolyticpassivation process used to increase the thickness of the natural oxidelayer on the surface of metal parts.

The process is called anodizing because the part to be treated forms the anode electrode of an electrolytic cell. Anodizing increases resistance to corrosion and wear, and provides better adhesion for paint primers and glues than bare metal does. Anodic films can also be used for a number of cosmetic effects, either with thick porous coatings that can absorb dyes or with thin transparent coatings that add interference effects to reflected light.

 

Types of anodising

1) Chromic Acid Anodising

Rarely used, but suitable for castings and in situations where a reduction in fatigue strength is not acceptable. Film thicknesses are the thinnest of the three common processes. However, it’s not ideal for when coloring is needed.

2) Sulphuric Acid Anodising

Used in a variety of occations. A range of oxide layer thicknesses can be achieved as can effective colouring, most commonly achieved by the application of a secondary colouring treatment. Film thicknesses in aluminium are in the range of 5-25 Microns, with 10-15 required for effective colouring using dyes. Coating thicknesses in titanium are significantly less, being in the range of 0.1-0.3Microns.

3) Hard Anodising

Hard Anodising is ultimately is the thickest form of anodising, creating an oxide layer which is between 20-100 Microns thick, depending on the base alloy being treated. It offers the highest increases in hardness, wear resistance and electrical resistance and is primarily a functional coating. It is also performed in a sulfuric acid solution, but with higher acid concentration, low temperature and a higher voltage applied.

 

Case Study: Issues we ran into when anodising:

-Fixation for anodisation/ jigging marks: It’s prone to corrosion and bruises.

-Blind holes: Electrolyte will not able to get into the blind holes, thus creating uneven appearances.

-Insufficient packaging/ impact while shipping the goods is likely to create marks.

 

Preventative measures:

-Reinforce inspection equipment: anodisation thickness testers, durometers, salt spray test machine

-Tapes applied to mask the area while anodising

-Reinfoce packaging sufficiency

 

Visit CNC Turning Parts , Stamping Parts  CNC Mahining Service  and Quality Inspection  to get more info about us. Technical Data for your reference

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