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http://hdl.handle.net/11375/24948
Title: | Coating of High Strength Steels with a Zn-1.6Al-1.6Mg Bath |
Other Titles: | Selective Oxidation and Reactive Wetting of High Strength Steels by a Zn-1.6Al-1.6Mg Bath |
Authors: | De Rango, Danielle M. |
Advisor: | McDermid, Joseph R. |
Department: | Materials Science and Engineering |
Keywords: | reactive wettting;advanced high strength steel;high strength steel;dual phase steel;selective oxidation;annealing process atmosphere;bare spot defects;bare spot;continuous hot-dip galvanizing;galvanizing;Zn-Al-Mg coating;Zn-Mg-Al coating;ZM coating;ZAM coating |
Publication Date: | 2019 |
Abstract: | Recently, Zn-XAl-YMg coatings have emerged as lighter-weight substitutes for traditional Zn-based coatings for the corrosion protection of steels; however, little is currently known concerning the interactions between the oxides present on advanced high strength steel (AHSS) surfaces and the Zn-Al-Mg bath. In the current contri- bution, the selective oxidation and reactive wetting of a series of C-Mn AHSS were determined with the objective of providing a quantitative description of this pro- cess. The process atmosphere pO2 was varied using dew points of −50◦C, −30◦C and −5◦C. The surface oxide chemistry and morphology were analysed by means of SEM and XPS techniques. Reactive wetting of the selectively oxidized surfaces using a Zn-1.6 wt.% Al-1.6 wt.% Mg bath was monitored as a function of annealing time at 60 s, 100 s and 140 s at 800◦C. The resulting bare spot defects in the Zn-1.6 wt.% Al-1.6 wt.% Mg coating were assessed by means of SAM-AES and FIB, while coating adhesion was analysed by 180◦ bend tests. Annealing the steel substrates resulted in the formation of surface MnO, which varied based on pO2 and Mn alloy content, and that this MnO greatly reduced the wettability of the steel by the Zn-1.6 wt.% Al- 1.6 wt.% Mg bath, resulting in bare spot defects. It was determined that the reactive wetting of the steel substrate was dependant on the oxide morphology and oxidation mode, which was a function of both alloying content of Mn in the steel and annealing pO2 process atmosphere (dew point). Finally, it was concluded that the bare spot area percentage on the coated panels was statistically invariant for annealing times of between 60 s and 140 s at 800◦C. |
URI: | http://hdl.handle.net/11375/24948 |
Appears in Collections: | Open Access Dissertations and Theses |
Files in This Item:
File | Description | Size | Format | |
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De_Rango_Danielle_M_2019Sept_MASc.pdf | 13.57 MB | Adobe PDF | View/Open |
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