Zn and Zn-Sn alloy coatings with and without chromate layers. Part I: Corrosion resistance and structural analysis

L. Sziráki, A. Cziráki, Z. Vértesy, V. Kiss, L. Ivanova, G. Raichevski, S. Vitkova, Ts Marinova

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

The aqueous corrosion resistances of Zn and Zn-Sn (approximately 20 wt % Sn) electrodeposits, passivated by immersion in chromating solution with different ratios of Cr(VI) to activating ions, are compared. The electrochemical behaviour of various chromated and nonchromated coatings were investigated in deaerated 0.5 mol dm-3 Na2SO4/pH 5 solution using a.c. impedance and d.c. polarization techniques. The polarization curves revealed that the chromate layers influence both the cathodic and anodic reactions. The corrosion rate of each specimen decreases with time due to the accumulation of corrosion products. The dark yellow (DY) chromate film on the Zn-Sn alloy and the iridiscent yellow (IY) on Zn yields the best protective ability in agreement with the assessment of prolonged salt spray chamber tests. These chromate layers resembling cracked mud become permeable to the electrolyte after immersion and, as a consequence of the transformation and the leaching of certain Cr compounds, a very porous agglomerate of corrosion products forms. The morphology and structure of dark yellow chromated Zn-Sn alloy was also investigated by transmission electromicroscopy (TEM) and scanning electronmicroscopy with microprobe (SEM/EDS) analyses before and after corrosion. The depth profile of the corroded surface chemical composition was determined by X-ray photoelectron spectroscopy (XPS).

Original languageEnglish
Pages (from-to)927-937
Number of pages11
JournalJournal of Applied Electrochemistry
Volume29
Issue number8
DOIs
Publication statusPublished - 1999

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Chromates
Structural analysis
Corrosion resistance
Corrosion
Coatings
Polarization
Corrosion rate
Electrolytes
Leaching
Energy dispersive spectroscopy
X ray photoelectron spectroscopy
Salts
Ions
Scanning
Scanning electron microscopy
Chemical analysis

ASJC Scopus subject areas

  • Electrochemistry

Cite this

Zn and Zn-Sn alloy coatings with and without chromate layers. Part I : Corrosion resistance and structural analysis. / Sziráki, L.; Cziráki, A.; Vértesy, Z.; Kiss, V.; Ivanova, L.; Raichevski, G.; Vitkova, S.; Marinova, Ts.

In: Journal of Applied Electrochemistry, Vol. 29, No. 8, 1999, p. 927-937.

Research output: Contribution to journalArticle

Sziráki, L. ; Cziráki, A. ; Vértesy, Z. ; Kiss, V. ; Ivanova, L. ; Raichevski, G. ; Vitkova, S. ; Marinova, Ts. / Zn and Zn-Sn alloy coatings with and without chromate layers. Part I : Corrosion resistance and structural analysis. In: Journal of Applied Electrochemistry. 1999 ; Vol. 29, No. 8. pp. 927-937.
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