I've recently finished my Daemon army, so I thought I would share with you how to make corrupted bases. It is very simple and effective, even hobby newbies can do this.
1. Get yourself some PVA glue. I used the below, though this exact stuff isn't required; I got this for free from my Dad as he works in the building trade.
2. Get some superglue. This is only cheap stuff and costs a bank busting £1 from a local discount shop. Depending how many bases you have and how much corrupted effect you want will greatly depend how much you use. My Daemon army has 61 based models and I used only half a tube of superglue, though majority of these were normal 25mm bases and I only had four 40mm bases.