Anodizing is a process of forming an oxide film on the surface of a metal by electrochemical means, which is mainly used to enhance the corrosion resistance, abrasion resistance and decorative properties of metals.
Author: Anna
Anodizing is a process of forming an oxide film on the surface of a metal by electrochemical means, which is mainly used to enhance the corrosion resistance, abrasion resistance and decorative properties of metals. The following is a summary of its key points:
Principle and Process
Electrochemical Principle: The metal (e.g., aluminum, magnesium, titanium) is used as an anode and placed in an electrolyte (e.g., sulfuric acid, oxalic acid), which oxidizes the surface of the metal by applying an electric current to form a dense oxide layer (e.g., aluminum oxide).
Steps: Metal pretreatment (cleaning) → Electrolysis reaction (anodic oxidation) → Dyeing (optional) → Closure treatment (sealing micropores with hot water or steam).
Features and Advantages
Performance Enhancement: Oxidized film is hard, corrosion and abrasion resistant, and has insulating properties.
Decorative: the microporous structure can adsorb dyes for diversified color choices.
Environmentally friendly: Some processes use environmentally friendly electrolytes (e.g. sulfuric acid instead of chromic acid).
Application areas
Industry: aerospace components, automotive parts (weight reduction and corrosion resistance).
Consumer electronics: cell phone and laptop housings (e.g. Apple products).
Architecture: window and door frames, decorative panels (weather resistant).
Types and Parameters
Ordinary anodizing: thinner oxide layer, suitable for daily protection and dyeing.
Hard anodizing: High voltage/low temperature treatment to form a thicker, harder layer for high wear environments.
Comparison with other processes
Difference with electroplating: anodizing generates its own oxide film, which is smaller in thickness but with improved performance; electroplating is an external metal layer, which changes the appearance or increases the thickness.
Applicable metals: Mainly “valve metals” (aluminum, magnesium, titanium), ferrous metals are not applicable.
Environmental impact
Wastewater treatment: Compliance is required to deal with waste liquids containing acids or heavy metals, modern processes tend to be environmentally friendly.
Anodizing is widely used in many industries to optimize surface properties and is an important surface treatment technology that combines functionality and aesthetics.