Designed Anodizing

ANODIZING 

Anodising is the general name applied to methods of treating metals, where the work piece is made the anode in an electrolytic cell, usually to form oxide coatings for the purpose of increasing the performance of the surface.
 
In the case of aluminium, the anodising process forms a layer of aluminium oxide - Al203 - or corundum, which is very hard, relatively inert, electrically insulating and can absorb dyes to colour the film. 
 
The anodic film itself grows at the aluminium / aluminium oxide interface by the continuous formation and dissolution of a layer of oxide, this is the so-called barrier layer and its thickness is a function of the process starting voltage. A porous, more structured layer forms on top of the barrier layer making up the rest of the coating.

Plating

Blue Passivate - Natural: Most often when a drawing specifies ‘Blue’ they are most often actually referring to a Natural or Clear Finish. Any Passivation process will affect the colour of the component and there is no such thing as a completely clear or colourless finish. Natural Passivate instead has a very light and iridescent blue colour. This isn’t strong enough to be instantly identifiable as "Blue" and certainly not as strong a colour as say, the sky. If you wished to have parts Zinc Plated that were identifiable as sky blue, then we could add a dye into the process to achieve this. Natural Passivation provides a good level of corrosion resistance for its cost.

Black Passivate: An option for a matte black finish, this finish is most often specified for decorative reasons although will also increase corrosion resistance.

Gold Passivate - Yellow: Gold Passivate is just another name for Yellow Passivate. Although it has Gold in its name, this process contains no actual Gold and is simply referring to the colour which can actually be a darker tone of yellow. Traditionally the colour of the coating was an indication of the amount of Hexavalent Chromium in the makeup of the solution and a ‘Stronger’ colour would in theory perform better, this may be one of the other reasons that companies specified Gold as opposed to Yellow. Yellow Passivates are most popular in the automotive industry for components such as Brake Calipers and Yellow Passivate provides better corrosion resistance than Clear/Natural Passivate.