Structures and characteristics of Cr(III)-based conversion coatings on electrogalvanized steels
Resource
Surface and Coatings Technology 203 (3-4): 317-323
Journal
Surface and Coatings Technology
Journal Issue
203
Pages
317-323
Date Issued
2008
Date
2008
Author(s)
Abstract
Trivalent chromium (Cr(III)) conversion coatings have been made on electrogalvanized steels in the solutions containing Cr(III) sulfate, nitrate, and chloride among which the sulfate, nitrate, and chloride anions function as passivating, oxidizing, and pitting agents, respectively. The structure and properties of the Cr(III) conversion coatings were examined by electrochemical methods and surface morphology observations. Experimental results showed that the Cr(III) coating formed in the sulfate bath displayed a thin, compact, single-layered structure, before and after baking. The conversion coating formed in the nitrate bath consisted of two porous layers for both the as-deposited and baked states. Moreover, the coating prepared in the chloride bath exhibited a porous, single-layered structure regardless of the baking treatment. Electrochemical impedance analyses further showed that the anions in the bath strongly influenced the structure and corrosion resistances of the Cr(III) coatings. © 2008 Elsevier B.V. All rights reserved.
Subjects
Anions effect; Electrogalvanized; Structure; Trivalent chromium conversion coating
SDGs
Other Subjects
Chlorine compounds; Chromium; Chromium compounds; Corrosion resistance; Ions; Nitrates; Structure (composition); Sulfur compounds; Zinc coatings; Anions effect; Cr-based conversion coatings; Electrochemical impedance analysis; ELectrochemical methods; Electrogalvanized; Electrogalvanized steel; Structure and properties; Trivalent chromium conversion coating; Coatings
Type
journal article
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