What is anodising?

Anodic oxidation, the electrochemical oxidation of metals or alloys. Aluminium and its alloys in the corresponding electrolyte and specific process conditions, due to the action of the applied current, the formation of a layer of oxide film on the aluminium products (anode) process. Anodic oxidation, if not specifically indicated, usually refers to sulphuric acid anodising.

In order to overcome the defects of aluminium alloy surface hardness and abrasion resistance, expand the application range and prolong the service life, the surface treatment technology becomes an indispensable part in the use of aluminium alloy, and the anodic oxidation technology is the most widely used and successful.

The so-called anodic oxidation of aluminium is a kind of electrolytic oxidation process, in which the surface of aluminium and aluminium alloys is usually transformed into a layer of oxide film, which has protective, decorative and some other functional properties. The anodic oxidation of aluminium from this definition includes only the part of the process that generates the anodic oxide film.

A metal or alloy part is used as an anode and an oxide film is formed on its surface by electrolysis. The metal oxide film changes the surface state and properties, such as surface colouring, improving corrosion resistance, enhancing wear resistance and hardness, and protecting the metal surface. Non-ferrous metals or their alloys (such as aluminium, magnesium and its alloys, etc.) can be anodic oxidation treatment, this method is widely used in machinery parts, aircraft and automobile parts, precision instruments and radio equipment, daily necessities and architectural decoration and other aspects.

Generally speaking, the anode is used aluminium or aluminium alloy as the anode, the cathode is selected lead plate, the aluminium and lead plate together in an aqueous solution, which has sulphuric acid, oxalic acid, chromic acid, etc., electrolysis, so that the surface of the aluminium and lead plate to form a kind of oxidized film. Of these acids, the most widely used is anodising with sulphuric acid.