Microstructural evolution and oxidation behavior of hot-dip 55 wt.% Al–Zn–Si coated steels

Luo, Qun; Li, Qian; Zhang, Jieyu; Hu-sheng, LU; Li, Lin; Chou, Kuo‐Chih

doi:10.1016/j.jallcom.2015.05.257

Cited by 15 publications

(5 citation statements)

References 36 publications

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“…The dross Al 8 Fe 2 Si (Zn), Fe-IMCs particles are recognised as τ5c and are main source of metal spot defects in the coated steel strip and flat products. Fine mushy dross particles of size up to 5 µm are entrapped in the overlay region of the Al-Zn coating [18,19]. Once flat steel strips passed through the final rolling step, τ5c Fe-IMCs experience compressive forces.…”

Section: Literature Reviewmentioning

confidence: 99%

Iron Intermetallic Compounds (IMCs) Formation Mechanism in the Molten Aluminium Zinc (Al-Zn) Coating Alloy

2024

Teh. vjesn.

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To prevent corrosion of steel products, the steel industry often relies on Al-Zn based alloy coatings, applied through hot-dip coating technology. Despite this, a long-standing problem in the galvanizing industry involves the formation of Fe-based intermetallic compounds (IMCs) in the Al-Zn coating bath, caused by iron dissolution from steel products. Such IMCs are the primary source of dross formation in the Al-Zn bath, which inevitably leads to metal spot defects in the coated steel products and bottom dross build-up in the Al-Zn bath. The present research aims to investigate the mechanism of Fe transformation into IMCs. To achieve this, Fe saturated and unsaturated Al-Zn alloys were doped with low carbon steel at a temperature of 600 °C. The samples were collected at regular intervals and quenched in water. The optical microscopy (OM) and scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDS) were used to study the transformation of steel strips into Fe-IMCs particles in molten Al-Zn alloys. The study findings suggest that the Fe transformation into Fe-IMCs is a complex process, where the steel strip surface is initially oxidized, and Al5Fe2 and Al3Fe are formed, which finally transform into Al8Fe2Si(Zn) (τ5c) IMCs particles. These results can assist galvanizers in understanding formation of Fe-IMCs and bottom dross build up in the costing pots.

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Section: Literature Reviewmentioning

confidence: 99%

Iron Intermetallic Compounds (IMCs) Formation Mechanism in the Molten Aluminium Zinc (Al-Zn) Coating Alloy

2024

Teh. vjesn.

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“…On the one hand, cathodic protection coatings act as a sacrificial anode to guard the substrate by making use of the potential difference between it and the substrate. On the other hand, the coating is also an excellent physical shielding coating, involving the shielding of the coating itself and the blocking of the corrosion products forming a film via the degradation of the coating [5].…”

Section: Introductionmentioning

confidence: 99%

Balanced Anti-Corrosion Action of Reduced Graphene Oxide in Zn-Al Coating during Medium-Term Exposure to NaCl Solution

Shi,

Wu,

Zhang

et al. 2023

Coatings

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Considering the electronegativity and shielding anti-sepsis characteristic of reduced graphene oxide (G), we design a Zn-Al coating with embedded G (Zn-G/Al) on low-carbon steel using the low-pressure cold spray (LPCS) method. In this method, G-coated Al powders (G/Al) prepared using in situ reduction and Zn powders were mixed as a raw material for spraying. Embedding G could boost the cathodic protection performance of Zn-Al (70 wt.% zinc and 30 wt.% aluminum) coating, as has been confirmed in previous work. In this work, the microstructure, composition and electrochemical parameters of Zn-G/Al coating during full immersion were measured to investigate G’s effect on the corrosion protection properties of the Zn-Al coating. The test results showed that embedded G could facilitate the generation of many corrosion products and pile on the coating surface to form a corrosion product film during full immersion. The corrosion product film on the Zn-0.2 wt.%G/Al coating surface demonstrated an excellent protective property, which reflects the fact that the Ecorr and icorr values for Zn-0.2 wt.%G/Al after 20d immersion (Ecorr = −1.143 Vvs.SCE, icorr= 49.96 μA/cm2) were lower than the initial value (Ecorr = −1.299 Vvs.SCE, icorr = 82.16 μA/cm2). It can be concluded that adding an appropriate amount of G to the coating can balance the cathodic protection and shielding property of the coating. The equilibrium mechanism was also analyzed in this work.

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“…The coating on the steel is a useful method to avoid oxidation and corrosion. [8,9] The coatings were generally produced on the steel for cold forming in early times. [10] As there are many advantages of coating, much effort has been devoted into developing new coatings on the hot stamping steel.…”

Section: Introductionmentioning

confidence: 99%

Effect of Heat Treatment on the Formability of Zn‐Coated Hot Stamping Steel

Zheng

et al. 2022

steel research int.

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Herein, the effect of heat treatment with die quenching on Zn‐coated hot stamping steel is analyzed. Heating temperatures are 850, 880, 900, and 930 °C, and soaking times are 4 and 8 min. Then, microstructure, hardness, coating layer morphology, element diffusion and distribution, formation of microcrack and microvoid, and oxidation are analyzed. Results reveal that as heating temperature increases, the Vickers hardness of Zn‐coated hot stamping steel increases when soaking time is 4 min, while it decreases when soaking time is 8 min. The least average hardness value is still larger than 460, resulting from the formation of the martensitic phase. The diffusion tends to be significant as heating temperature and soaking time increase. Both the diffusion and the evaporation affect the thickness of the coating layer remarkably. The average layer thickness is at least 18.2 μm. Microcrack generates in the coating layer due to different thermal expansions between substrate and coating layer and the melting of Zn or Zn–Fe binary phase with high content of Zn. Microvoid forms in the coating layer, resulting from the Kirkendall effect and oxidation of the Zn element. Moreover, with the increase in heating temperature and soaking time, Fe2O3 is also generated on the coating surface along with ZnO.

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Microstructural evolution and oxidation behavior of hot-dip 55 wt.% Al–Zn–Si coated steels

Cited by 15 publications

References 36 publications

Iron Intermetallic Compounds (IMCs) Formation Mechanism in the Molten Aluminium Zinc (Al-Zn) Coating Alloy

Iron Intermetallic Compounds (IMCs) Formation Mechanism in the Molten Aluminium Zinc (Al-Zn) Coating Alloy

Balanced Anti-Corrosion Action of Reduced Graphene Oxide in Zn-Al Coating during Medium-Term Exposure to NaCl Solution

Effect of Heat Treatment on the Formability of Zn‐Coated Hot Stamping Steel

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