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Communication Dans Un Congrès Année : 2023

Reduction of molten zinc corrosion of batch hot-dip galvanizing hooks thanks to zincophobic coatings

Résumé

Batch hot-dip galvanizing is a surface treatment used to protect steel from atmospheric corrosion. In order to ensure this, metal parts are coated by dipping in liquid zinc alloy bath. However, hangers that allow their transfer between several galvanizing surface treatment baths undergo the same treatment and consequent molten zinc corrosion on a recurring basis. Additionally, the zinc layer formed on those hangers consumes zinc and necessitates a supplementary stripping step in hydrochloric acid. This treatment generates additional economic and environmental costs. 316L steel and ceramic coatings, such as WC-Co [1, 2], are used in continuous galvanizing to protect rollers from this type of corrosion, however those materials are either too expensive or too brittle to be employed in batch hot-dip galvanizing. By extrapolation of the works in continuous galvanizing showing that SiO2 reduces wetting in liquid zinc [3], the idea was to produce a protective uniform SiO2 layer at the coating’s surface. Simple Si coating cannot be used due to thermodynamic limitations, so a more complex coating composition was adopted. A slurry process was used to create a Fe-Cr-Ni-Si base coating. Cyclic galvanizing tests on coated low-alloyed DD13 steel showed that the corrosion rate is 9 times slower than it is on uncoated samples of the same steel. Moreover, because of the much-reduced wettability of zinc, up to 85% of the zinc alloy is saved after 20 galvanizing cycles. Therefore, less HCl is needed to remove the zinc layer off the hangers. In order to understand the mechanism of protection, SEM-EDX investigations were carried out on samples that underwent various numbers of galvanizing cycles. The SiO2 formation hypothesis was confirmed and the role of different coating phases was examined.
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Dates et versions

hal-04123124 , version 1 (09-06-2023)

Identifiants

  • HAL Id : hal-04123124 , version 1

Citer

Aleksandra Cieplak, Ingrid Proriol Serre, David Balloy. Reduction of molten zinc corrosion of batch hot-dip galvanizing hooks thanks to zincophobic coatings. 12 th Asia Pacific General Galvanizing Conference (APGGC), Apr 2023, Yokohama, Japan. ⟨hal-04123124⟩
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