Which acid is used in the anodising process?

Correct option is B

The correct answer is (b) Dilute Sulphuric Acid

Explanation:

• Anodising is an electrochemical process used to enhance the thickness and durability of the oxide layer on the surface of metals, mainly aluminium.
• The most commonly used acid for this process is dilute sulphuric acid (H₂SO₄) because it efficiently produces a hard and corrosion-resistant anodic layer.
• In this process, aluminium acts as the anode, and when an electric current is passed through the dilute sulphuric acid solution, it results in the formation of a protective oxide layer.

Information Booster:

Why is anodising done?

• To prevent corrosion by forming a protective oxide layer.
• To enhance surface durability and resistance to wear.
  To allow better adhesion of paint and dyes for colouring aluminium surfaces.
  To give a decorative finish to metals.

Common Uses of Anodising:

• Aircraft parts
• Automobile components
• Cookware (such as anodised aluminium utensils)
• Electronic gadgets (like smartphone bodies)

Other Acids Used in Anodising:

• Chromic Acid – Used for corrosion-resistant coatings.
• Phosphoric Acid – Used for adhesive bonding applications.

Additional Knowledge (Other Options):

• Dilute Acetic Acid: It is mainly used in food preservation and vinegar production.
• Dilute Hydrochloric Acid: Hydrochloric acid (HCl) is a strong corrosive acid that destroys the oxide layer instead of forming one.
• Dilute Nitric Acid: Nitric acid (HNO₃) is used for cleaning and passivation of stainless steel.