Abstract
The reaction mechanisms and the structures of the phases formed during the hot dipping of iron in 0 to 10 pct Al-Zn alloy baths at temperatures of 450° to 700°C were studied by X-ray diffraction and electron microprobe analysis techniques. A new mechanism for the inhibition reaction between iron and zinc is proposed. At bath temperatures below 600°C, a thin layer of an Fe-Al-Zn ternary compound forms on the iron surface and inhibits the growth of Fe-Zn phases. Breakdown of inhibition occurs during the dipping process when the ternary compound becomes rich in aluminum and transforms to a more stable structure which is isomorphous with Fe2Al5. While this breakdown is occurring, the zinc atoms react with iron and form the conventional Fe-Zn phases.
In 1 to 10 pct Al-Zn baths at temperatures≥600°C a very violent, highly exothermic reaction occurs during hot dipping. This type of process is due to the electronic bond rearrangements which occur during the formation of the intermetallic Fe2(AlZn)5. This intermetallic forms from the reaction of aluminum-bearing FeZn7 with the Zn-Al alloy bath.
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Ghuman, A.R.P., Goldstein, J.I. Reaction mechanisms for the coatings formed during the hot dipping of iron in 0 to 10 Pct Al-Zn baths at 450° to 700°C. Metall Trans 2, 2903–2914 (1971). https://doi.org/10.1007/BF02813270
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DOI: https://doi.org/10.1007/BF02813270