Geoff Mackenzie wrote:
I've got some ali castings which are an absolute bugger to clean - all
nooks and crannies, even a toothbrush won't do the job. Have heard
rumours of an electrolytic process which sounds ideal, but can't find
out anything further.

Anything known? Does it work? Where can I get it done?

TIA,

Geoff MacK
I've only ever run across electrolytic de-rusting of iron and steel
parts although electrolytic polishing processes do exist for other metals.

Some electrolytic de-rusting links

http://www.davidbradley.net/ERR.html
http://antique-engines.com/electrol.asp

Not likely to be applicable to aluminium though as the slightly alkali
solution may attack the aluminium. I've often used alloy wheel cleaner
or jenolite for cleaning aluminium, basically phosphoric acid IIRC with
some additions to aid cleaning.