This is a new notion for me. I'm sure it is a term familiar to most readers. However, just in case, this is my version of what it means. To understand it you need to appreciate that there is an hierarchical order of metals determined by their 'nobility'. A sacrifical anode is less a noble metal which is used to attract impurities away from more noble metals that you do not wish to be eroded. Thus if you wish to avoid erosion in your copper boiler, you can put a sacrificial anode in the water which will attract the impurities in the water and keep them away from your noble boiler. The link between multicultural artworkers and sacrificial anodes is entirely my own!