The Repair of Wrought and Cast Iron Work - Dublin City Council

IRON THE REPAIR OF WROUGHT AND CAST IRONWORK
used, stainless steel (which can be joined mechanically
or by welding) is preferable to mild steel due to its
superior corrosion resistance (although it is harder to
work by hammer).
Repairs that use mild steel may be less effective and
are not likely to last as long as a similar repair using
wrought iron and appropriate traditional detailing. In
the long term, using mild steel for conservation work
does not make sense. By saving in the short term,
higher costs are likely to be incurred at a later date
because of mild steel’s inferior corrosion resistance
and it should therefore only be used as a last resort.
Mild steel has the added disadvantage of being
manufactured according to the metric rather than the
imperial measuring system which means that
replacement mild steel bars for railings, for example,
will not exactly match existing wrought iron bars.
However, the reality is that wrought iron may be
beyond the budget of many private individuals. The
simplest solution in such cases is to carry out only
those repairs that are absolutely necessary, for
example where an element or missing element is
causing or contributing to structural unsoundness. The
condition of the existing ironwork may often be
stabilised without replacing any of the historic
wrought iron.
removed and that the quality of the casting is good
(for example, that the two halves of the casting align
correctly) before being put in place.
It is advisable to inspect patterns before they are used
for making castings to ensure that the detailing is
accurate and that the surface finish is smooth
(Image courtesy of Historic Scotland)
Where a different metal has to be used, it should be
isolated wherever possible by an inert insulating
material such as nylon sleeves or washers. Future
maintenance should take special care to keep such
areas well-painted to guard against corrosion.
REPLICATING CAST IRONWORK
New castings should be cast using the traditional
green sand mould technique. Original ironwork should
not be used as the pattern for making a mould as this
is likely to reduce the sharpness of detail and surface
quality of the resulting casting. Cast iron shrinks by
approximately 1%, therefore the resulting casting
would also be smaller than the original component it
was meant to replicate. Original ironwork can instead
be used as a reference or template for a new pattern
to be made. Hand-carved timber patterns are
preferable, although some foundries also make
patterns out of different materials such as resin.
Patterns should be checked before the castings are
made to ensure that the surface finish and detailing is
of good quality. Once the castings have been made,
they should be checked to ensure that any flashing
(sharp edges of waste iron that can form around the
joint line of the mould during casting) has been
Castings should be checked before they are put in
place to ensure that they are of acceptable quality.
The casting illustrated above is deformed because the
two halves of the mould were not aligned correctly
during the casting process
Aluminium is not an appropriate substitute for grey
cast iron
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