The corrosion and electrochemical properties of three zinc single crystal surfaces and two types of polycrystalline zinc surfaces have been investigated. Near-neutral 1M ammonium sulfate solutions under de-aerated and aerated conditions were used as the corrosion medium. The purpose of these studies was to examine the effect of surface orientation on the corrosion process. Corrosion measurements were made mostly using DC polarization techniques. The corrosion rates on the three zinc single crystal surfaces were found to be similar in de-aerated solutions. Slight differences were obtained in aerated solutions where the corrosion rate of the (0001) surface was lower compared to the (1010) and (1120) surfaces, which corroded at similar rates. Overall corrosion rates for all three surfaces were much higher under aerated conditions compared to the de-aerated conditions. The two types of polycrystalline surfaces also showed similar corrosion rates in the de-aerated solutions.;The overall reactions taking place during cathodic polarization for both single crystal and polycrystalline surfaces under de-aerated and aerated conditions agreed with the results of other investigators. During anodic polarizations under de-aerated conditions, single crystal surfaces gave results indicating a different reaction mechanism from those obtained for polycrystalline surfaces under de-aerated conditions and single crystal surfaces under aerated conditions. Several possible reaction mechanisms were given to explain these results.;The morphological studies on various corroded surfaces were carried out using SEM techniques. SEM micrographs of corroded surfaces clearly revealed preferential corrosion taking place. The morphologies appeared quite different when different surface orientations were viewed, but were consistent with a reaction which prefers ;AC impedance measurements carried out on various zinc surfaces showed that under de-aerated conditions the electrode-electrolyte interface can be represented reasonably well by a simple equivalent circuit characteristic of a charge transfer controlled processes. Additional processes occurred in aerated systems.;The morphological studies carried out on the electrodeposits made on various zinc surfaces showed epitaxial growth on the sample surfaces producing different morphologies depending on the original exposed surface. Also the morphologies obtained from various zinc surfaces after corrosion and deposition seem quite similar.
展开▼
