# What's happening to carbon electrodes?

Carbon electrodes are very popular, because unlike metal electrodes, carbon is quite inert during electrolysis (I'm sure that has some explanation based on electronegativity).

However they too are not eternally lasting. Especially the pencil graphite bars will slowly release black chunks into the solution.

My question is, what's happening them. The black chunks seem like carbon, so it's probably not reacting. What's damaging the structure?

This article here indicates that carbon/graphite electrodes are attacked both chemically (oxygen gets converted to $\ce {CO2}$, removing carbon from the electrode) and mechanically (gas bubbles form in pores in the surface and break it apart). Pencil leads fall apart quickly because of the clay content. A high-quality graphite electrode will last far longer but will also eventually decay. The rate of erosion goes up rapidly with increased voltage across the electrodes. In my personal experience doing water electrolysis I got almost no mechanical erosion at 10V but obvious mechanical erosion at 24V.