Application of electrochemical impedance spectroscopy in characterization of structural changes of printing plates

The porous structure of the aluminium oxide surface of lithographic printing plate (PP) has a most significant influence on the quality of the imprints. This study presents the results of application of electrochemical impedance spectroscopy (EIS) in characterization of PPs' porous structures and their changes during chemical processing. Two common PP types—thermal and conventional—were investigated. The influence of the processing solution’s working age on topographical changes of PP surface and associated change in the impedance spectra are investigated and discussed. The equivalent electrical circuit models reproducing the observed EIS spectra are proposed. Based on these models two mechanisms of surface’s topography changes responsible for degradation of PP performance due to the processing are identified and discussed.