POMIA Pohang Institute of Metal Industry Advancement

Pohang, South Korea

POMIA Pohang Institute of Metal Industry Advancement

Pohang, South Korea
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Oh M.-S.,POSCO | Kim S.-H.,POSCO | Kim J.-S.,POSCO | Lee J.-W.,POMIA Pohang Institute of Metal Industry Advancement | And 2 more authors.
Metals and Materials International | Year: 2016

The effects of Mg and Al content on the microstructure and corrosion resistance of hot-dip Zn-Mg-Al alloycoated steel sheets were investigated. Pure Zn and Zn-based alloy coatings containing Mg (0-5 wt%) and Al (0.2-55 wt%) were produced by a hot-dip galvanizing method. Mg and Al addition induced formation of intermetallic microstructures, like primary Zn, Zn/MgZn2 binary eutectic, dendric Zn/Al eutectoid, and Zn/Al/MgZn2/ternary eutectic structures in the coating layer. MgZn2-related structures (Zn/MgZn2, Zn/Al/MgZn2, MgZn2) played an important role in increasing the corrosion resistance of Zn-Mg-Al alloy-coated steel sheets. Zn-3%Mg-2.5%Al coating layer containing a large volume of lamellar-shaped Zn/MgZn2 binary eutectic structures showed the best cut-edge corrosion resistance. The analysis indicated that Mg dissolved from MgZn2 in the early stage of corrosion and migrated to the cathodic region of steel-exposed cut-edge area to form dense and ordered protective corrosion products, leading to prolonged cathodic protection of Zn-Mg-Al alloy-coated steel sheets. © 2016, The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.


Min J.,POMIA Pohang Institute of Metal Industry Advancement | Min J.,Pohang University of Science and Technology | Sohn H.-K.,POMIA Pohang Institute of Metal Industry Advancement | You Y.,POMIA Pohang Institute of Metal Industry Advancement | And 3 more authors.
18th International Corrosion Congress 2011 | Year: 2011

A phosphate conversion coating was formed on the surface of Zn-Mg alloy coated (ZM) steel by immersing the specimen in a phosphating solution. The characteristic changes of the coated specimens were investigated with variations of the phosphating time. The results show that Mg is dissolved from Zn-Mg alloy coating layer by acidic solution during phosphate treatment and then the dissolved Mg ions have participated in formation of the phosphate layer. Very fine and dense phosphate crystals were formed on Zn-Mg alloy coating due to the Mg ions and corrosion resistance of coatings were also increased.

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