Electrodeposition of zinc from an alkaline non-cyanide bath:: Influence of a quaternary aliphatic polyamine

The effect of a quaternary aliphatic polyamine (QAA) on zinc electrodeposition in an alkaline non-cyanide medium was investigated using voltammetry and chronoamperometry. Addition of QAA to the zinc solution led to a decrease in the exchange current density (i(0)), suggesting that QAA inhibits the zinc reduction process. This was confirmed through a study of the initial stages of crystal growth using atomic force microscopy (AFM), which revealed that the crystals grew with a multilayer structure. Such a structure is characteristic of crystals grown in the presence of an organic compound that acts as an inhibitor. X-ray diffraction analysis of the zinc coatings showed that the presence of QAA in the solution favored the growth of crystals with a (101) orientation. Coatings grown in solutions containing QAA had a smaller grain size than crystals grown in QAA-free solutions. As a result, coatings were compact and shiny. Zinc coatings grown in the presence of QAA displayed lower corrosion rates compared to those grown in the absence of QAA. This effect was attributed to a change in overall crystal morphology (i.e., multilayer growth, change of crystal orientation and decrease in grain size) due to the presence of QAA in solution.