This is a set of curves for different alloys at 18 ASF. I will explain them as well.

This is 6061, 2024, 7075, and 1100 (as a reference). For anodizing purposes, they will be essentially the same for any 6xxx, 2xxx, 7xxx, and 1xxx alloy.

The current density was held to 18.000 ASF (yes, 3 decimal places) in all cases, and the electrolyte temp. was held to 70.4 deg. F. +/- 0.3 deg. F. (my cooling system will do this).

The electrolyte was the "professional" 9.4% by volume mix.

Notice that the curves slope upward for 1100 and 6061, the "easy" alloys. The curves for 2024 and 7075 slope downward, the "difficult" alloys. Also notice that each alloy has its own characteristic bulk resistance (OSF).

The vertical axis is in Ohms per sq.ft. (OSF). You can calculate what the voltage would be for your size of work as follows:

OSF x 1/SF = Ohms, this simplifies to: OSF / SF = Ohms

The voltage for your work is then: V = A x Ohms

SF is the surface area of the work in square feet.

A is the actual current you apply to the work to get the ASF that you want.

What makes the curves slope up or down is the combination of coating thickness and pore size, more thickness makes it go up, and larger pore size makes it go down. Unfortunately we can't separate them and look at each individually while the anodization is proceeding.

The curves that slope up show that coating growth is staying ahead of dissolution. Notice that these have the thickest coatings. When the curves slope down dissolution is winning the race, and the coatings are thinner.

This means for 9.4% (by volume) electrolyte, better results could be had by increasing the current density (speeds up growth) reducing the acid concentration (reduces dissolution) or by decreasing the temperature (reduces dissolution). Increasing the current density would be the easiest to do.

BTW, the 2024 and 7075 samples both showed signs of excessive dissolution (powder coming off when dry) 2024 was the worst.

The graphs are in the Album (button at the top) how do you make this work?

(edited to include the formulas)

This is 6061, 2024, 7075, and 1100 (as a reference). For anodizing purposes, they will be essentially the same for any 6xxx, 2xxx, 7xxx, and 1xxx alloy.

The current density was held to 18.000 ASF (yes, 3 decimal places) in all cases, and the electrolyte temp. was held to 70.4 deg. F. +/- 0.3 deg. F. (my cooling system will do this).

The electrolyte was the "professional" 9.4% by volume mix.

Notice that the curves slope upward for 1100 and 6061, the "easy" alloys. The curves for 2024 and 7075 slope downward, the "difficult" alloys. Also notice that each alloy has its own characteristic bulk resistance (OSF).

The vertical axis is in Ohms per sq.ft. (OSF). You can calculate what the voltage would be for your size of work as follows:

OSF x 1/SF = Ohms, this simplifies to: OSF / SF = Ohms

The voltage for your work is then: V = A x Ohms

SF is the surface area of the work in square feet.

A is the actual current you apply to the work to get the ASF that you want.

What makes the curves slope up or down is the combination of coating thickness and pore size, more thickness makes it go up, and larger pore size makes it go down. Unfortunately we can't separate them and look at each individually while the anodization is proceeding.

The curves that slope up show that coating growth is staying ahead of dissolution. Notice that these have the thickest coatings. When the curves slope down dissolution is winning the race, and the coatings are thinner.

This means for 9.4% (by volume) electrolyte, better results could be had by increasing the current density (speeds up growth) reducing the acid concentration (reduces dissolution) or by decreasing the temperature (reduces dissolution). Increasing the current density would be the easiest to do.

BTW, the 2024 and 7075 samples both showed signs of excessive dissolution (powder coming off when dry) 2024 was the worst.

The graphs are in the Album (button at the top) how do you make this work?

(edited to include the formulas)

## Comment