INVESTIGADORES
ELSNER Cecilia Ines
artículos
Título:
Control of the growth of zinc-iron phases in the hot-dip galvanizing process
Autor/es:
J.D. CULCASI; P.R. SERÉ; C.I. ELSNER; A.R. DI SARLI
Revista:
SURFACE AND COATINGS TECHNOLOGY
Editorial:
ELSEVIER SCIENCE SA
Referencias:
Lugar: Amsterdam; Año: 1999 vol. 122 p. 21 - 23
ISSN:
0257-8972
Resumen:
Zinc-iron
phases may develop at the steel substrate/zinc coating interface during the
hot-dip galvanizing process. There phases are hard and brittle, and make the
material unsuitable for the forming process. Growth of the zinc-iron phases
could be controlled adding 0.18 to 0.30% of aluminium to the galvanizing bath,
which reacts with iron to produce a thin layer of intermetallic Fe2Al5. The
latter hinders alloying between the steel sheet and molten zinc, and is
therefore referred to as the inhibition layer since it inhibits or retards the
formation of Fe-Zn phases. Nevertheless, this layer is unstable and local
growth of Fe-Zn phases (out-burst) is found at longer immersion times. This
out-burst phenomenon depends on many factors, such as the chemical composition
of both the bath and the steel, and the immersion time.
The aim of
the work was to investigate the influence of both immersion time and a small addition
of titanium to the galvanizing bath on coating characteristics. Thus, plain
carbon steel sheets were galvanized with alloys A and B, which has different
chemical compositions. The immersion time was varied between 1 and 120s.
Cross-sections of samples were observed by scanning electron microscopy. The
analysis showed that, even for very short immersion times, samples galvanized
with alloy A developed out-bursts whereas those with alloy B showed, for the
same immersion time, bigger grains than the ones galvanized with alloy A.
However, for both alloys, the intermetallic development was greater for longer
immersion time. Such observations suggest that a small amount if titanium could
serve as a catalyst for the iron-aluminium reaction, allowing a greater
development of the inhibition layer and delaying growth of the Fe-Zn
intermetallic.