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

IRON THE REPAIR OF WROUGHT AND CAST IRONWORK
APPLYING PAINT
If paint is not properly applied to ironwork, or if the
surface has not been correctly prepared to receive the
paint, the new coating will be less effective and may
even fail. Ironwork can usually be cleaned and painted
more effectively in workshop conditions. However,
budget and time constraints may prohibit this, and it
may be unnecessary if there is little corrosion or
damage to the existing paint. The decision to remove
ironwork should also be balanced against the
potential damage that its removal could cause to
adjoining masonry or to the ironwork itself. This is
particularly relevant with regard to wrought iron, as it
is usually necessary to break many of the joints in
order to dismantle wrought ironwork.
Whether ironwork is painted indoors or outdoors, it is
important that it is absolutely dry before paint is
applied. If there is any moisture within the iron (due to
rainfall, dew, or even high relative humidity) this will be
trapped beneath fresh layers of paint and is likely to
cause corrosion within a short period of time. In
general, ironwork should not be painted outdoors
between December and February, as damp conditions
and low temperatures can hinder the curing of paint.
Painting in windy conditions must also be avoided as
wind-blown dirt and dust may damage fresh coatings
of paint.
For larger projects, it is essential to get the paint right.
The specification of paint should be chosen carefully,
and, whatever system is chosen, it should be applied in
a controlled environment. This will ensure that the iron
is completely dry before the paint is applied, and will
also prevent any wind-blown dust and dirt from
damaging the paint while it is drying. Generally, handapplication
of paint by brush is better than spraying as
it is more effective at reaching sections that are out of
the line of sight. For paint to be effective, an adequate
number of coats must be applied. When painting bare
metal, use at least two coats of primer, followed by at
least one base coat and a top coat. Several layers of
primer can be far more effective than an expensive
top coat.
Coats must be applied in thin layers, allowing each to
dry thoroughly before the next coat is applied. This
prevents solvents evaporating from the layer
underneath and damaging subsequent coats painted
on top. If paint is applied too thickly it obscures detail,
is unlikely to cure properly, and will be less effective as
a result. Paint that is improperly applied to uneven
surfaces may bridge depressions and hollows instead
Over-thick application of paint will obscure detail
and result in less effective protection
of adhering to them. This causes air to be trapped
between the paint and the metal, making the paint
more prone to cracking and flaking. When dealing
with traditional galvanised corrugated iron, a mordant
wash or chemical etching primer is required to help
the paint to adhere to the galvanised surface.
If ironwork has been painted off-site, a final inspection
should be conducted once the ironwork has been
reinstated. This will ensure that any localised areas of
damage that may have occurred during transit and
assembly are identified immediately and can be
repainted in situ to prevent these becoming weak
points in the new coating.
This photograph shows a set of railings a month
after they were painted. Corrosion material was not
thoroughly removed before the application of paint
resulting in the localised failure of the new paint
18