That's my understanding of anodic layer "hardness" as well.
There is a lower limit in current density however; at some current density below 2 A/sq.ft., the pores become so large that a reasonable pore structure won't form, and the anodize falls off or fails to form at all. At 2 A/sq.ft. the pores are too large for dyeing and/or sealing, and the part won't retain the dye. This is why the lower limit for LCD is specified as 3 A/sq.ft.
The colorless characteristic of LCD will permit dyeing in shades previously thought impossible. The commercial dyes will need to be adjusted, because they have been blended to account for the yellowish standard anodizing tint.
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