THE CORROSION OF ALUMINUM IN HALOGENATED HYDROCARBON SOLVENTS

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.