Steve...
In the boatyards we use a couple acid washes - ZING is one brand, EZ ON/EZ OFF is another - and both are available at most marine stores. I can verify that they will clean and brighten anodized aluminum but will dull mill aluminum. If left on too long however the metal will turn a chalky white on the surface. Both of these products are a weak mixture of muriatic acid (hydrochloric acid) and other solvents/cleaners. You could buy a gallon jug of muriatic at any hardware store or Home Depot and mix a 50/50 concentration and try it on a scrap piece of metal left over from your build. Normally we go to great lengths to avoid getting any acid on metals because boat owners get testy when we dull their shiny toys.
Dave