Some results have been obtained dealing with the corrosion in an alkaline medium of zinc that has been passivated in a chromic phosphate solution, the treatment of which serves to increase the resistance of zinc to corrosion in humidity-laden surroundings. The behaviour of pure zinc in the same environment is also considered as a reference. Emphasis in this study has been placed on the application of electrochemical techniques, particularly to the polarization curves and impedance diagrams. The effects of immersion time, agitation, disc rotation speed and prior cathodic polarization are interpreted.