Abstract
Corrosion behaviour of Sn (0.0, 0.5, 1.0, 2.0 and 3.0 wt.%)-doped Zn 1.6 wt.% Al 1.6 wt.% Mg alloys exposed to salt spray testing was investigated. Intergranular corrosion was observed for all alloys in both as-cast and annealed states. However, due to microstructure spheroidisation in the annealed samples, potential intergranular corrosion paths are significantly reduced. Samples with 0.5 wt.% of Sn showed the best corrosion properties. The main corrosion products identified by XRD analysis for all samples were simonkolleite and hydrozincite. Occasionally, ZnO and AlO were identified in limited amounts.
Highlights
A wide range of commercial Zn-based hot-dip coatings are used for corrosion protection
There is an inherent difference in the open circuit potential (OCP) of these phases mainly compared to the η(Zn) phase (Figure 13)
There is an inherent difference in the open circuit potential (OCP) of these phases mainly compared to the η(Zn) phase protection to the η(Zn) phasethe dendrites
Summary
A wide range of commercial Zn-based hot-dip coatings are used for corrosion protection. Mg addition to binary Zn-Al alloys results in the formation of intermetallic phases such as Zn2 Mg and Zn11 Mg2 These phases are more corrosion active even compared to the η(Zn) phase, enabling the more effective cathodic protection of steel substrates [17]. They are formed within eutectics in the interdendritic areas of primary η(Zn) dendrites. These phases are enabling the cathodic protection of this Zn-based matrix, overall corrosion attack starts as the intergranular (IG)
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