Properties of zinc coatings electrochemically passivated in sodium molybdate

Molybdenum compounds are considered to be promising, environmentally friendly substances for passivation of zinc coatings. Conversion coatings on electroplated zinc coatings obtained by cathodic polarization of a solution of molybdate of sodium with the addition of phosphoric acid are studied. These...

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Bibliographic Details
Published in:Surface and interface analysis 2018-12, Vol.50 (12-13), p.1310-1318
Main Authors: Akulich, N., Ivanova, N., Zharskii, I., Jönsson‐Niedziółka, M.
Format: Article
Language:English
Subjects:
Cathodic coating (process)
Cathodic polarization
Chemical composition
Conversion coating
Conversion coatings
corrosion
Corrosion resistance
Corrosion resistant steels
Electrochemical impedance spectroscopy
electrochemical passivation
Electrode polarization
Galvanized steel
Galvanized steels
Galvanizing
Hydroxides
Metal hydroxides
Molybdenum compounds
Morphology
Organic chemistry
Phosphates
Phosphoric acid
Protective coatings
Sodium molybdate
Spectrum analysis
X ray spectra
zinc coating
Zinc coatings
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Summary:Molybdenum compounds are considered to be promising, environmentally friendly substances for passivation of zinc coatings. Conversion coatings on electroplated zinc coatings obtained by cathodic polarization of a solution of molybdate of sodium with the addition of phosphoric acid are studied. These coatings had a pronounced needle‐shaped structure and were homogeneous. X‐ray photoelectronic spectroscopy analysis showed that zinc hydroxides and phosphates, Mo (VI), and Mo (V) compounds are present in the conversion coating. As part of this study, the influence of the current density and deposition time of the coating on the surface morphology and the chemical composition of conversion films was determined. Polarization measurements and electrochemical impedance spectroscopy have shown that the investigated coatings significantly increase the corrosion resistance of galvanized steel in chloride‐containing solution.
ISSN:0142-2421
1096-9918
DOI:10.1002/sia.6525