Effect of Cold-Sprayed Zinc Coating and Heat Treatment on the Microstructure and Corrosion Behavior of 30MnB5 Hot-Stamped Steel

TL;DR

This study examines how cold-sprayed zinc coating and heat treatment affect the microstructure and corrosion resistance of a specific type of hot-stamped steel.

Contribution

The novel finding is that cold-sprayed zinc forms protective intermetallic compounds during heat treatment, enhancing corrosion resistance through a sacrificial anode effect.

Findings

Cold-sprayed zinc coating combined with heat treatment forms Fe–Al and Zn–Al–Fe intermetallic compounds.

Zinc corrodes preferentially, acting as a sacrificial anode to protect the steel and underlying Al–Si coating.

Heat treatment leads to uniform redistribution of Zn, improving coating layer integrity and corrosion behavior.

Abstract

This study investigated the microstructure and corrosion behavior of 30MnB5 hot-stamped steel after applying a zinc coating using the cold-spraying method followed by heat treatment (HT). Al-10 wt%Si coating is essential for improving the high-temperature corrosion resistance of 30MnB5 steel during the hot-stamping process. Before HT, the coating layer primarily consisted of Al, whereas after HT, Fe–Al-based intermetallic compounds were formed throughout the layer. The Zn in the coating layer applied using the cold-spraying method was not uniformly distributed before HT. However, during HT, the low-melting-point Zn melted and re-solidified, allowing it to combine with Fe diffusing from the substrate. Consequently, Zn–Al–Fe-based intermetallic compounds were formed on the surface of the coating layer. In the Zn-coated specimens, the current density near the corrosion potential tends to be lower than that of the Al–Si-coated specimens because Zn corrodes preferentially owing to its sacrificial anode effect, thereby protecting the underlying Al–Si-coated layer and steel.

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