Thanks for the cleaning aid tip.
@MyQul yes, I'm taking over the lease on a property that was a restaurant and there are some empties there. As there are no supplier labels etc on the kegs, and I have no idea of the who or where of the previous occupants, I thought rather than toss them out I would put them to good use in my own brewing. I have a local brewery that will be supply all my keg and bottle beer for retail. I did mention the empties to the brewery rep and they were not interested in the empties. Shame to see them go to waste.
I never realised there was such a problem with beer kegs being stolen. Do you know if this problem is mainly down to the scrap value of the metal. Many years ago when I worked on the roofs we were always seeing lead and zinc nick from sites.