A roll coating tungstate passivation treatment for hot-dip galvanized sheet steel
Resource
Surface and Coatings Technology, 205(21-22), 5124-5129
Journal
Surface and Coatings Technology
Pages
5124-5129
Date Issued
2011
Date
2011
Author(s)
Abstract
A tungstate passivation treatment was performed on hot-dip galvanized steel via a roll coating process. The effect of anion (phosphate and nitrate) in the tungstate solution on the microstructure and corrosion resistance of the passive film was explored. The surface morphology of the GI steel slightly changed after roll coating using tungstate/phosphoric and tungstate/nitric solutions. Cross-sectional transmission electron microscope characterization revealed that the passive film prepared by the tungstate/phosphoric solution consisted of a thin compact layer, whereas that prepared by the tungstate/nitric solution was relatively thick and porous. The reduction of tungstate anion to low-valent tungsten oxide and metallic tungsten was also observed. Compared with nitrate anion, the presence of phosphate anion in the solution resulted in zinc phosphate, less metallic tungsten, and more hexavalent tungsten species in the passive film. As a result, the passive film prepared by the tungstate/phosphoric solution displayed a better corrosion resistance than that prepared by the tungstate/nitric solution, as evaluated by polarization measurement and salt spray test. © 2011 Elsevier B.V.
SDGs
Type
journal article
File(s)![Thumbnail Image]()
Loading...
Name
152.pdf
Size
23.45 KB
Format
Adobe PDF
Checksum
(MD5):aff1fc6bfcfac082b569a4b0ee612613