Electron Conditioning of Technical Aluminium Surfaces: Effect on the   Secondary Electron Yield
  The effect of electron conditioning on commercially aluminium alloys 1100 and 6063 were investigated. Contrary to the assumption that electron conditioning, if performed long enough, can reduce and stabilize the SEY to low values ($\leq 1.3$, value of many pure elements), the SEY of aluminium did not go lower than 1.8. In fact, it reincreases with continued electron exposure dose. 
F. Le Pimpec, F. King, R.E. Kirby