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Some very powerful analytical tools have been developed within this project to characterize galvanized and galvannealed coatings:
-Selective chemical dissolution technique in combination with depth profiling.
-Transmission electron microscopy (TEM) on cross sections with a special preparation technique.

In terms of galvannealing behaviour and galvannealed-coating adhesion, a model was developed to explain the interaction between steel chemistry, Zn-Fe reactivity and coating adhesion respondent powdering behaviour. The validity of this model was proven by using a new phosphate treatment to control the galvannealing reactivity and powdering behaviour. This was done at an industrial hot-dip-galvanizing line. However, before this technology can be transferred to hot-dip-galvanizing lines on a regular basis, different aspects have to be clarified.

The formation of the Fe-Al interface layer was studied in detail. A strong correlation between zinc bath aluminium concentration, strip entry temperature, zinc bath temperature and dipping time on the thickness, structure and zinc content of the Fe-Al interface layer was found. Based on these results, samples with distinct coating properties were produced at an industrial line. The investigation of the spot weldability of these samples indicated that there is a significant influence even for slight variations. These results, based on one trial, have to be confirmed in future investigations.

Hot-dip-galvanising simulation experiments performed on three different simulators proved the good comparability of different laboratory simulation facilities in terms of the formation of the Fe-Al interface layer and the Zn-Fe growth at the interface.erface.

Additional information

Authors: ESSING A, Thyssen Krupp Stahl AG, Dortmund (DE);SCHUHMACHER B, Thyssen Krupp Stahl AG, Dortmund (DE);DAVIES D, British Steel, Port Talbot (GB);ANGELI J, Voest-Alpine Stahl Linz GmbH, Linz (AT);STRUTZENBERGER J, Voest-Alpine Stahl Linz GmbH, Linz (AT);FADERL J, Voest-Alpine Stahl Linz GmbH, Linz (AT)
Bibliographic Reference: EUR 20042 EN (2001), pp.89. Euro: 13.00
Availability: Available from EUR-OP sales agents. URL:
ISBN: ISBN:92-894-2064-2
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