Galvanic Zn-Mn alloys - electrodeposition, phase composition, corrosion behaviour and protective ability

The electrodeposition conditions and the peculiarities of the phase composition of Zn-Mn alloys with different contents ( similar to 6 and similar to11 wt.%) of the alloying component are described and discussed. Their corrosion behaviour and protective ability are investigated in a model medium of free aerated solution of 5% NaCl in open circuit conditions as well as under external anodic polarization-potentiodynamic polarization curves, polarization resistance (RP) measurements, etc. The results obtained are compared to these of pure zinc galvanic coatings. For determination of the corrosion products of the layers X-ray diffraction as well as X-ray photoelectron spectroscopy are used. As a result the compound zinc hydroxide chloride monohydrate (ZHC)-Zn-5(OH)(8)Cl-2.H2O-is registered on Zn-Mn alloys. ZHC supplement increases the corrosion resistance due to its low product of solubility and ensures better protective ability. Some suggestions about the protective action of the manganese are also given. (C) 2003 Elsevier Science B.V. All rights reserved.