magnesium sharpener

Unfortunately I don’t know too much about chemistry. Even though the Bavarian school system provided me with 13 years of education ^[1]I think this has now been reduced to 12 years., the type of school I went to and the modules I picked meant that I only ever had one semester of chemistry – so please forgive me and correct me if I am using the wrong words in this blog post.

A few days ago I noticed that my magnesium sharpeners look pretty bad. The surface is now very rough, not shiny any more at all, except for some small areas. The sharpeners have been stored together with a silver plated letter opener I bought very cheap from The Pen Shop. A few erasers were also next to the sharpeners for a long period of time. I’m now wondering what caused the corrosion/tarnishing of the magnesium.

Maybe someone who knows more about chemistry can tell me what happened – so that I can avoid similar mistakes in the future.

My first idea what might have happened: A process similar to the one when aluminium is used to clean tarnished silver took place. The magnesium sharpeners kept the silver-plated letter opener untarnished, because magnesium is less noble than silver and therefore attracted sulphur or other chemical elements.

My alternative suggestion: Just like the chemicals from another eraser ‘ruined’ one of my wooden pencil boxes once, the chemicals from the erasers that were stored together with the magnesium sharpener changed the sharpeners’ surface, too.

Can anyone tell me what really happened to the magnesium sharpeners?