Can anodizing be used to roughen a surface to a given finish surface finish?

A. The safest way to apply a roughness to a plate like yours is to texture or chemically etch it. There are several texture houses in the west coast that can apply any of the several thousand different patterns available (dots, bumps, striations, splines, etc.) in almost any depth you may desire. Regarding warpage I don't think it could be a problem. In most kitchens there are hot plates for stoves and ovens that show no warpage after years exposed to direct flame.

A. I would be against anodize as a means of achieving a controlled surface finish in that there is too much variability during pretreatment and anodizing to ensure a consistent 80-100 RA after anodize. For instance, alkaline etching vs. non-etch cleaning vs. acid etching will give varying surface condition prior to anodizing. Anodizing alone will vary given temperature, applied voltage, electrolyte temperature, etc. I would be more in favor of mechanical finish via Timesaver or brush finishing - akin to blasting but without associated bending of sheet.

A. A finish spec of 80-100 (pretty darned tight spec for such an arbitrary measurement as Ra) should be achievable with anodizing, but it will involve either a heavy etch prior to coating, or a rough sanding (perhaps with 220 grit, or rougher, AL203 sandpaper) prior to coating. This will take a little R&D on yours, and your coaters part. You didn't mention the type of anodizing you are trying to apply, or the thickness, both of which have a bearing on the final Ra data. If I were you, I would start off sanding sample pieces to different Ra's, and send to your coater, have him process all the parts at once, and see what works, or see if tweaks need to be made. I would provide your coater with a wide range of samples, both above, and below your finished RA spec. Typically you will double the original (uncoated part) Ra on a 2 mil hardcoat, this will lessen as the coating gets thinner. However, when starting with a rough surface, the typical anodizing process tends to have the opposite effect, and can actually will smooth the surface, due to etching, and the substrate dissolving during the anodizing step. Make sure you are using a coater that has very tight quality control, if you want a repeatable process.

A. In addition to what Milt said, you must know that under heat the aluminum substrate expands 5 times that of the aluminum oxide on top, and cracks occur.