Calculating theoretical thickness while anodising aluminium oxide

• Mar 25, 2023

• #1

lforster02

1

0

I am trying to calculate the theoretical thickness of an anodised coating. I know all values apart from I am unsure whether to use 2e or 6e for the amount of electrons.

Anode reaction as follows: 2OH = H2O + O + 2e

the aluminium reactions preferentially with the one O atom, using equation: 3O + 2Al (anode) = Al2O3

There is 2 electrons transferred in the anode reaction, although 3O consumed to produce the coating Al2O3, which means 6e is transferred. Does anyone have any idea whether to use 6 or 2 in the formula: thickness = (1/density) x ((molecular mass x current x time) / (area x number of e x faradays constant))

Attached are the relevant reactions

 

Last edited by a moderator: Mar 25, 2023

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• Mar 25, 2023

• #2

mjc123

Science Advisor

Homework Helper

1,323

725

If you are using the molar mass of Al₂O₃, then you need to use the number of electrons consumed per Al₂O₃ produced, i.e. 6.

 

1. How is the theoretical thickness of anodized aluminum oxide calculated?

The theoretical thickness of anodized aluminum oxide is calculated using the following formula:

Thickness = (Voltage x Time) / (Current Density x Oxide Density)

Where voltage is the applied voltage during anodizing, time is the duration of the anodizing process, current density is the current per unit area, and oxide density is the density of aluminum oxide (2.7 g/cm3).

2. What factors can affect the accuracy of theoretical thickness calculations?

The accuracy of theoretical thickness calculations can be affected by various factors, such as variations in the anodizing process (e.g. voltage fluctuations, uneven current distribution), impurities in the aluminum alloy, and variations in the oxide density.

3. Can the theoretical thickness of anodized aluminum oxide be different from the actual thickness?

Yes, the theoretical thickness of anodized aluminum oxide may differ from the actual thickness due to variations in the anodizing process and other factors that can affect the accuracy of the calculation.

4. How can one improve the accuracy of theoretical thickness calculations?

To improve the accuracy of theoretical thickness calculations, it is important to carefully control the anodizing process and minimize any potential sources of error. This includes ensuring a stable voltage and current, using high-quality aluminum alloys, and accurately measuring the oxide density.

5. Is the theoretical thickness of anodized aluminum oxide the same for all types of aluminum alloys?

No, the theoretical thickness of anodized aluminum oxide may vary depending on the type of aluminum alloy being anodized. This is because different alloys can have different impurity levels and oxide densities, which can affect the calculation of theoretical thickness.