I did something similar to what A J suggests...I was given a Saito .80 that was in sad shape. I completely dis-assembled it, and bolted just the case, cyl. and backplate together and sand blasted it w/ fine sand at low air pressure. I got the finest silica sand the concrete contractor guys have, and use one of those siphon type guns that you stick the pick-up tube into a bucket of sand. It was something like 15-20 bucks (back a few years ago) got it from Harbor Freight as I recall. If you use as low an air press. as will siphon the sand, it works well, and will not erode the alum. if you use a "washing" or "dusting" motion...Came out looking as good as new!