The behaviour of aluminium in 1,1,1-trichloroethane has been examined
to determine conditions for the initiation of so-called bleeding corro
sion and reasons for continued activity. Aided by the use of supportin
g electrolyte to enhance solution conductivity, it is evident that lit
tle reaction between aluminium and the solvent proceeds unless the air
-formed film is mechanically damaged. However, mechanical damage per s
e is insufficient to allow continued reaction; thus, sufficiently high
anodic potentials are also required in polarization studies. In natur
al immersion studies, the onset of bleeding corrosion is associated wi
th a marked anodic excursion in potential, with dramatic net cathodic
currents developed for specimens that were originally anodically polar
ized. Mechanisms for such behaviour suggest the requirement to sustain
sufficiently large regions of bare metal, where solvent reduction out
strips repassivation in the inevitable presence of water in the solven
t.