Composition of the corrosion products of galvanic alloys Zn–Co and their influence on the protective ability

The composition of the corrosion products of non-chromated and chromated galvanic coatings of Zn and Zn–Co(1–5wt.%) alloys in free aerated solution of 5% NaCl is described and discussed. Corrosion treatment is realized at open circuit conditions for different periods of time. The corrosion products of monolayer galvanic coatings were investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). As a result of the treatment the compound zinc hydroxide chloride monohydrat (ZHC)—Zn5(OH)8Cl2.H2O—was registered on Zn–Co alloys after the experimental period. ZHC supplementary increases the corrosion resistance due to its low solubility product and ensures better protection. In addition, the protective ability of mono- and bilayer galvanic systems (chromated and non-chromated) was determined using polarization resistance measurements.