Surface Preparation for Anodising

When an item is anodised, it will show the surface exactly how it is. I.E. If the surface has sand marks or scratches in it, they will be present once anodised. If the surface is polished and in excellent condition, it will show this when finished.

It is for this reason, that we advise you to prepare your products to the finish you require. Our staff do make slight adjustments to a finish such as smoothing out a scratch, but unless it is requested by the customer, it will be anodised "as is".

Please refer to the "types of finishing" page for assistance with the type of finish that meets your requirements. If you require further assistance, please feel free to contact our staff.

Common Issues with Preparation

Alkaline etching

This is caused in one of two ways

1. The item is machined with a coolant that isa heavy alkaline. 

Some coolants within machines have a PH between 8 - 9.5.If left on components, this can cause etching that is unseen by the eye. Once the component is etched within our processes, the etching is seen as black spots on the surface. Once the etching has occurred, it can not be removed without further machining.

2. Item is wet from the coolant or an alkaline/acidic substance, and placed/stored on a surface that does not draw the moisture away from the component.

Two of the worst aluminium grades for this are 2xxx and 7xxx series and tends to occur on the machined end grain of the metal. 

There are a number of ways to alleviate this.

A. Use a PH neutral coolant or corrosion additives.

B. Wash the component in soapy water then rinse straight after machining.

C. Aviation use iso-propol alcohol or other water dispersant after the drying stage. (eg WD40)

Hazing of polished parts

Polishing is a very temperamental process. If it is done correctly, the result "Can" be like chrome. If not, the results can be chalk and cheese.

Couple of issues that can cause these issues:

  • Polish used - do not use animal fat based polishes. They tend to cause issues with the surface finish and conflict with chemicals used in the anodising process.

  • The polish process - Preparation is the key. Don't rush the preparation prior to polishing.

  • The anodising process - There are a number of changes that can be made within the anodising process to promote a quality finish. We make these changes on all polish jobs, but it is only as good as the preparation prior to anodising.

Featured Picture:

A car trim was used for the demonstration as they are the worst for the hazing. The featured car trim is anodised and ready to fit at this stage.

Left is prepared by an external vendor

Right is prepared by DNA Anodising.

Same part, Same anodising process. Big results

Trim example.jpg