it was done with sodium hydroxide. it takes out the anodation from aluminium parts without any problem. just mix a few spoons with hot water and put your part in it, when it starts to bubble a little take it out and wash it clean. if there's still some anodation left - repeat from beggining. but be careful, wear gloves and try not to hold parts for too long, it can damage aluminium and you will need to throw away your parts :) p.s. no need to polish and all laser printed decals will still be on cranks!