The type of anodic oxidation can be classified from the dimensions of electrolyte composition, current form and film nature, the following are the main classification and typical representatives:
Author: Anna
The type of anodic oxidation can be classified from the dimensions of electrolyte composition, current form and film nature, the following are the main classification and typical representatives:
I. Classification according to electrolyte composition
Sulfuric acid anodic oxidation
The electrolyte is mainly sulfuric acid, and the oxide film generated is The thickness is about 5-20μm, transparent and colorless, with high hardness, good corrosion resistance and easy dyeing. It is suitable for surface treatment of aluminum alloy and is the most widely used type.
Oxalic acid anodic oxidation
Using oxalic acid solution, the oxide film is thicker (up to 60μm), yellow, with low porosity and excellent corrosion resistance, but the cost is higher.
Chromic Acid Anodizing
Electrolyte containing chromic acid, thin film (2-5μm), gray or milky white, poor abrasion resistance but dense and corrosion resistant, mostly used in special demand scenarios.
Phosphoric acid anodizing
Generates porous oxide film with large pore size, commonly used in electroplating or bonding pretreatment.
Mixed acid anodizing
such as sulfuric acid / oxalic acid mixture, combining the advantages of a variety of acids, can be adjusted according to the performance requirements of the formula, comprehensive cost and effect.
II. Classified according to the form of current
DC anodic oxidation
Voltage stability, uniform oxide film and strong adsorption, is the mainstream process.
AC anodic oxidation
Suitable for special metal or composite treatment, less application.
Pulsed current anodic oxidation
Enhancement of film density and corrosion resistance by intermittent current, commonly used in the preparation of hard oxide film35.
III. Classification according to the nature of the film
Ordinary anodic oxidation
Film thickness 5-25μm, microhardness HV300 or less, used for daily protection and decoration (e.g., architectural aluminum, electronic product shells).
Hard anodic oxidation
Film thickness up to 150μm, hardness HV300 or more, wear-resistant, suitable for mechanical parts, molds and other heavy-duty scenes.
Porcelain Anodizing
The film is ceramic texture, both high hardness and insulation, used for precision instruments or electronic components.
Micro-arc oxidation (plasma electrolytic oxidation)
Ceramic oxide film is generated through high-voltage micro-arc discharge, with hardness and corrosion resistance far exceeding that of conventional processes, and is used in aerospace, marine and other high-demand fields.
IV. Other Classification Methods
Natural coloring anodic oxidation: Generate colored film layer directly through organic sulfonic acid solution without additional dyeing.
Blocking layer anodizing: Formation of dense semiconductor oxide film, used for capacitors and other electronic devices.
There are various types of anodic oxidation, and the selection should be based on the metal material, performance requirements (such as hardness, corrosion resistance) and cost considerations. Sulfuric acid anodizing occupies a mainstream position due to its mature process and low cost, while hard and micro-arc oxidation are more advantageous in high-performance scenarios.