The Ferritic Solution - Euro Inox

oxidation ReSiStance
unlike the two above types of corrosion, high-temperature
cyclic oxidation is “dry corrosion” occurring at high
temperatures (>500°c) and in oxidizing atmospheres, with
or without thermal cycle.
when stainless steels are heated, their chromium content
forms a protective chromium oxide surface “scale” that
delays further oxidation. the scale and the metal substrate
will have different thermal expansion behaviour, which can
affect the scale’s stability, especially in service conditions
of frequent thermal cycling. the expansion coefficient of
the scale is very low and if that of the metal is too high,
excessive scale will be generated, which will spall or crack
when the metal cools and contracts.
thanks to their lower thermal expansion coefficient,
ferritic grades are much less prone than austenitic alloys
to high-temperature cyclic oxidation scaling. where there
is no spalling or cracking, there is no new oxidation. this
is a particular advantage in applications such as heating
systems, burners or exhaust systems, including manifolds.
bRoad appLication poSSibiLitieS
these interesting corrosion-resistance properties are far
from being ferritic stainless steel’s only attractions. they
are already enough, however, to win friends for ferritics in
the current climate of high material costs.
close examination of the properties of ferritics tends to
pay dividends. Some existing austenitic users might find, on
examining their specification, that a ferritic grade is actually
highly appropriate for their application.
Gymnasium roof, in grade 445, S. Korea.
…ferritic grades are much less
prone than austenitic alloys
to high-temperature cyclic
oxidation scaling.
potential stainless steel users may be surprised by the
exceptional qualities of ferritics – and discover that stainless
steel is a viable option after all!
Life cycLe coStinG: an invaLuabLe Guide
the value of carrying out a life cycle costing study on any
potential application cannot be stressed too highly. Such
a study will often reveal that stainless steel – generally
seen as a costly solution – is actually the lower-cost option,
viewed long-term.
Stainless steel’s corrosion resistance means longer life,
less maintenance, higher resale value, better appearance,
etc. it renders painting or galvanizing unnecessary. and as
if this were not inducement enough, the lower investment
cost of ferritic grades can be a clinching argument in favour
of stainless steel as a material choice.
already widely used and respected, ferritic grades are
nonetheless still being “discovered”. the numerous well-
proven existing applications, however, light the way to many
exciting new possibilities for these fine steels.
Burner, in grade 430.
…the lower investment cost of
ferritic grades can be
the clinching argument in
favour of stainless steel…
Manifold, in grade 441.