Mechanisms of formation and growth of intermetallic layer during hot dipping of iron in Zn–3Al and Zn–6Al baths

Abstract

The formation of the intermetallic layer during the hot dipping of iron in Zn–3Al and Zn–6Al baths has been studied using X-ray diffraction and scanning electron microscopy (SEM) techniques. Compositional images obtained by SEM proved to be essential for the detection of the initial, so-called inhibiting layer, which was detected even at the shortest dipping time (2 s at 450°C). The localized and abnormal growth of this layer causes it to break away from the iron surface and change the freezing characteristics of the adjacent liquid by creating a localized depletion of aluminium. At long dipping times, a columnar-like intermetallic of composition near that of the inhibition layer was detected.

MST/386