# 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.

## Key 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.