Coating substrate relationship after initial electrolyte contact in the electrodeposition of zinc on steel

Electron backscatter diffraction (EBSD) measurements show epitaxial electrochemical deposition of zinc on non-deformed and contrariwise random growth on deformed steel grains. Therefore, electrochemical investigations on the differences of zinc electrodeposition on electropolished respectively on temper rolled low carbon steel sheet of the same substrate are studied. These measurements show great differences in ECN (electrochemical noise) investigations and the 1st cycle of a CV (cyclic voltammetry) only. It is found, that the immersion of the substrate in the electrolyte prior to the measurements causes this behaviour. SEM, EDX, XPS (X-ray photoelectron spectroscopy), SAM (scanning Auger microscopy) and IRRAS (infrared reflection absorption spectroscopy) measurements are used for surface characterisation and EBSD-measurements for determination of crystallographic orientation to reveal the influence on electrochemical growth. It is proven that zinc precipitates form on the temper rolled substrate during immersion and cause a nucleation process prior to electrodeposition and the subsequent change in electrocrystallisation as zinc is deposited on zinc instead of steel. The differences in the electrochemical measurements are well described by this theory.