Barrier-type, nanocrystalline anodic films have been formed on a ZE41 magnesium alloy under a constant current density of 5 mA cm(-2) in a glycerol/fluoride electrolyte, containing 5 vol.% of added water, at 293 K. The films contain magnesium, fluorine and oxygen as the major species, and lower amounts of alloying element species. The films grow at an efficiency of similar to 0.8 to 0.9, with a formation ratio in the range of similar to 1.2 to 1.4 nm V-1 at the matrix regions and with a ratio of similar to 1.8 nm V-1 at Mg-Zn-RE second phase. At the former regions, rare earth species are enriched at the film surface and zinc is enriched in the alloy. A carbon- and oxygen-rich band within the film suggests that the films grow at the metal/film and film/electrolyte interfaces. (C) 2014 The Authors. Published by Elsevier Ltd.