Well this has probably been covered in previous post but i I will post it here just in case it may be of interest.
I needed to clean up/ de rust the checker plate for the shelves. I decided that the best way to go about it was to place the plates in a citric acid bath, but the problem was nothing I had was either long enough or wide enough.
Whilst pondering the problem I spotted my wife's plastic trays she uses for growing tomatoes, quick measure up and they are ideal.
So if you need a simple fairly shallow bath then those trays from B&Q @£6 provide a simple solution.