MST Steel Corp.: Innovations in Steel Coating Revolutionize Galvannealed Sheet Properties with Fe-Zn Alloy Coating

Introducing a groundbreaking development in steel coating technology, the Fe-Zn alloy coating on Galvannealed (GA) steel sheets enhances their corrosion resistance, paintability, and weldability. GA steel sheets have gained prominence in automobile applications due to these superior properties. To further enhance these characteristics, an electroplating process, known as flash coating, has been developed to apply a bright and adherent Fe-Zn alloy coating on GA steel sheets.
The electroplating process, with a reduced time of less than 10 seconds, ensures practical applicability in industrial coating lines by modulating the bath composition. Operating at a current density of 200-500 A/m², the process yields higher cathode current efficiency of 85-95%. Comparative studies with bare GA steel sheets demonstrate significant improvements in weldability, frictional behavior, phosphatability, and defect coverage with the Fe-Zn alloy-coated sheets.
Performance results highlight the superiority of Fe-10 wt.% Zn-coated GA steel sheets, with enhanced spot weldability, lower dynamic coefficient of friction (0.06-0.07 in lubrication), and improved corrosion resistance compared to bare GA steel sheets. Additionally, the Fe-Zn alloy-coated sheets exhibit uniform phosphate coating with globular crystal sizes ranging from 2-5 µm, comprising mainly of hopeite, along with spencerite and phosphophyllite compounds.
This innovative Fe-Zn alloy coating represents a significant advancement in automotive steel technology, offering enhanced performance and durability in GA steel sheets for various applications.
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