Issue 48

C. Bellini et alii, Frattura ed Integrità Strutturale, 48 (2019) 740-747; DOI: 10.3221/IGF-ESIS.48.67 746 Figure 6 : Mapping of the elements in the GS500-Coating interface. Figure 7 : Thermal crack and graphite dissolution. C ONCLUSION n this work, a traditional DCI is used to investigate the kinetic formation of the intermetallic phases in coatings obtained by traditional Zn bath. The investigated dipping times (15, 60, 180, 360 and 900 s) are chosen in order to investigate the thicknesses of each intermetallic phase and of the whole coating, both at lower and at higher dipping time. The results in terms of achieved thicknesses are very interesting. The minimum coating thickness is more than two times bigger than the thickness of steel coating in traditional dipping time (60 s). For all the investigated dipping times, the main phases observed is the ζ one, and mainly for the highest dipping time the η phase is negligible. The presence of graphite nodules in the DCI generates a sort of migration of nodules from the substrate to the coating. In many cases the graphite migrates without other phenomena, but in a few cases the graphite derogates generating voids or voids with low content of carbon. The thermal damage observed is due to the brittle behaviour of the δ phase, but all the thermal cracks propagate in the δ toward the δ-ζ interface that is a crack arresting. R EFERENCES [1] Vitkova, St., Ivanova, V., Raichevsky, G. (1996). Electrodeposition of low tin content zinc-tin alloys, Surf. Coat. Tech., 82, pp. 226-231. DOI: 10.1016/0257-8972(95)02662-2. I