I wouldn't call the "90 minute Rule" a rule, and I wrote it, its a guideline.
4.5 A/sq.ft. is the center of the published LCD range; which is 120 min at 3A/sq.ft. on the low end, to 60 minutes at 6A/sq.ft. on the high end. These times are based on the "720 Rule" for anodization time, and are intended to produce a layer 0.5 mils thick. A good general number for Type II intended for dyeing. PAR can be illusive if your operating conditions aren't right, I would suggest that you follow the 720 rule.
Sanding/grinding, or polishing an anodized layer can be hazardous to the layer if the work can flex or oilcan, just like with any other thin ceramic.
|