Jack Aubert asked: > >A couple of questions... > >1. Is it OK to leave the piece in the anodizing bath for a long period... >I mean does it have to be removed when it's "done" or will it continue to >"cook" and spoil the finish somehow.
If you allow the anodic film to continue building it will eventually take on a lumpy 'orange peel' surface. > >2. Since the easiest way to get DC without rigging up any electronics is >to just hook up a 12 volt automobile battery, could one just a 12 volt >automobile battery and leave the piece in longer? I don't have a handy >source of 16 volt DC, and would have to either buy something ready-made or >rig it up from parts. I've no experience of using a constant-voltage source so I can't really comment in detail but I suspect you may have problems. For the first few minutes of the process the voltage would fluctuate pretty wildly so it had to be 'chased' with the variable control to maintain 16 volts. We had the luxury of a continuously variable 0-20 volts 8amp AC/DC supply so this was easy. I'd just try it and see what happens. That's how I began. If you have an old 'open frame' 12V transformer it's fairly easy to add a few extra turns to put in series with the secondary winding to boost the voltage. A couple of other memories while I'm writing. The film is extremely hard and increases the rigidity of the workpiece markedly. If you want a curved workpiece then bend it before anodising. While it will resist abrasion, a sharp point can be forced through the film into the soft aluminium underneath. A piece of kitchen foil becomes very stiff and brittle when anodised. Try not to disturb the workpiece once anodising has begun. If electrolyte seeps into the joint with the connecting wire the joint itself will anodise and cut off the workpiece (the film is an insulator). The wire will then 'burn' at the liquid surface. Best Wishes T.
