The corrosion behavior and the microstructure of thermally treated stoichiometric Nd-Fe-B alloys with 1-3 at.% Al additions have been investigated. The additions improve the corrosion resistance in acid environment as well as in humid air at 150 o C whereas the smallest amount of Al resulted in the lowest corrosion rate. Large annealing times were found to increase the corrosion resistance in acid environment additionally, whereas it deteriorates the corrosion resistance in humid air.