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)-Zn-5(OH)(8)Cl-2.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. (C) 2002 Elsevier Science B.V. All rights reserved.