Acid in Anodising Process

The anodising process is an electrochemical technique used to increase the thickness of the natural oxide layer on the surface of metal parts.

Anodising Acid Selection

This process is commonly used for materials like aluminum, titanium, and magnesium.

The choice of electrolyte is crucial for the quality of the oxide layer formed.

Common Anodising Acid

• The most widely used acid for the anodising process, particularly for aluminum, is dilute sulphuric acid (H₂SO₄).
• Other acids like chromic acid or phosphoric acid can be used for specific applications, but sulphuric acid is the standard for general-purpose anodising.

Reasoning

Dilute sulphuric acid is preferred because:

• It effectively dissolves the metal surface, allowing for the formation of a porous oxide layer.
• It produces a hard, durable, and corrosion-resistant oxide coating.
• It is relatively inexpensive and readily available.
• The process parameters (like voltage, temperature, and concentration) are well-established for achieving desired coating properties.

Therefore, dilute sulphuric acid is the primary choice for the anodising process.