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1. ANODIZING
NAME:RATUL MIA
ID:199018
Presented by
Dhaka University of Engineering and
Technology, Gazipur.

2. What is Anodizing?
Anodizing is an electrolytic passivation process
used to increase the thickness of the natural oxide
layer on the surface of metal parts that Converts the
metal surface into decorative , durable , corrosion-
resistant , anodic oxide finish.

3. What is Anodizing?
Aluminum is ideally suited for Anodizing
,although other nonferrous metals ,such
as Magnesium and Titanium also can be
anodized.

4. PRINCIPLE
Anodizing

5. Types of Anodizing
Type-1:Chromic Acid Anodizing.
Type-2:Sulphuric Acid Anodizing.
Type-3:Hard Acid Anodizing.

6. Anodizing Process

7. Anodizing Process
(Reaction)
The reaction mechanism can be divided into
three stages:
Stage 1 : Metal dissolution
Al 𝐴𝑙3+ + 3𝑒−
Stage 2: Dissociation of water and 𝑂2−
ion
formation
2𝐻2𝑜 ⇄ 𝐻3𝑜+
+ 𝑂𝐻−

8. Anodizing Process
(Reaction)
2𝑂𝐻− ⇆ 𝐻2𝑜 + 𝑜2−
𝐻3𝑜+ ⇆ 𝐻2𝑜 + 𝐻+
Stage 3 : Formation of Alumina 𝐴𝑙2𝑂3(Exothermic Reaction)
2𝐴𝑙3+
+ 3𝑂2−
→ 𝐴𝑙2𝑂3

9. Anodizing—Structure

10. SEALING

11. ANODIZING DYES
Anthraquinone – Blues, Greens (Fig. 1)
Metalized Azo – Reds, Browns, Yellows, Oranges (Fig 2)
Metal Free Azo – Violets, Bright Reds
Sulphonated Coumarin – Bright Yellows (Fig. 3)

12. Benefits of Anodizing
Protects Satellite from the harsh environment of Space.
Revolutionized the construction of computer Hardware.
Elevated Hardness(600HV compared to 100-200HV for untreated
alumina alloy)
Improve resistance to wear ,more brittle than non anodized.
Color stability
Lower initial finishing cost.
Health and Safety

13. Application
NASA Space Station trusses and handrails
 Food preparation Equipment.
 Motor Vehicle Equipment
 Structure and Architectural categories.
Box Chain Necklace Food processing

14. Aluminum-bodied car