The Effect of Si on the Intermetallics Formation during Hot Dip Aluminizing

Abstract:

When applying an aluminium coating on a steel substrate, the corrosion resistance of aluminium is combined with the mechanical properties of steel. There are different ways to coat steel among which hot dipping is the most applied because it is technically feasible in large volumes and economically the most beneficial one. Although aluminized steel accounts for about 5% of the total world production of all hot dip coated steels, the interactions between the molten aluminium and steel substrate are not yet completely understood. During hot dipping, several intermetallic layers are formed between the outer nearly pure aluminium layer and the steel substrate. These layers mostly comprise of a thin FeAl3 and a thicker Fe2Al5 layer. The thickness of these intermetallic layers must be kept minimal since they embrittle the coating. Thickness reduction of the intermetallics is mainly realized by silicon addition to the aluminium bath. In this work, the formation of intermetallic layers was investigated for a deep drawing steel grade which was hot dipped in aluminium baths with six different Si contents ranging from 1 to 10 wt%Si. The Si-addition was demonstrated to lead to a decrease in the thickness of the intermetallic layers and a flattening of the intermetallic-steel interface. An increase in Si also led to the formation of other intermetallic compounds, which are investigated by a systematic analysis by scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD) on multiple samples and discussed in terms of the Si-effect on a possible formation mechanism for the intermetallics.

• Periodical: Advanced Materials Research (Volume 922)
• Pages: 429-434
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.922.429
• Online since: May 2014
• Authors: Babs Lemmens*, Beril Corlu, Joost de Strycker, Kim Verbeken
• Keywords: Aluminum (Al), Hot Dipping, Intermetallic, Silicon, Steel

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