Anodizing or Anodization is a common CNC aluminum parts surface treatment technology that applies the electrochemical process, in this guide, we'll introduce an improved aluminum alloy anodizing method and process in chromic acid solutions. 

Aluminum Anodizing Techniques

The aluminum and aluminum alloy chromic acid anodizing coating is an insulating film, when the aluminum products need to be conductive, the local area of the anodized aluminum parts should not have the films after anodizing. The traditional method to remove the anodized coating is to use a brush to dip in the insulating glue and evenly coat the parts to be protected to avoid contacting the anodizing solution. Process：apply insulating glue -> anodizing -> remove the glue. But this method has some shortcomings as below: 

1) It's a manual process, which makes the shape of the protection area is poor, the circle may become a triangle, square, diamond, etc. 

2) The process is complex and the cycle is long, it needs to be coated three times and dried, and then removed after anodization.

3) During the anodizing process, the insulating adhesive for local protection may fall off due to temperature and various factors. 

What is Chromic Acid Anodizing?

Chromic acid anodizing is the electrochemical process of thickening the natural thin oxide layer on aluminum surface in chromic acid solution, then improve the scratch and corrosion resistance of aluminum parts. 

Why Use Chromic Acid Anodizing of Aluminium Alloys?

The purpose of aluminum alloy anodizing in chromic acid is to improve the regularity of the edge of the protection area, simplify the process, shorten the processing period, and avoid the product quality degradation caused by the falling off of the insulating adhesive.

Advantages and benefits of anodized aluminum:

- Attractive appearance

- Minimum maintenance

- Highly durable layer

- Revolutionized the construction

- Environmental friendly

- Protects objects from the harsh environment

- Color stability

- Lower finishing cost

How to Anodize Aluminum and Aluminum Alloy with Chromic Acid?

Check out the steps of the chromic acid anodizing process of aluminium in detail.

1. Anodize the surface of aluminum parts with the chromic acid solution according to the method specified in HB/ Z118-87.

2. Remove the anodized film on the parts where do not need anodizing: use hydrofluoric acid content ≥ 40% as the solution to remove the film on the parts:

2.1. Select the thin felt to make its shape similar to the parts without protection, and fix it on the end of the wooden pole;

2.2 Take the wooden pole by hand, dip the thin felt at the end of the wooden pole into hydrofluoric acid solution, press it on the parts where do not need to be protected, and the stay 10 seconds to 20 seconds

2.3 Wash and dry the parts with water.