The Repair of Wrought and Cast Iron Work - Dublin City Council
The Repair of Wrought and Cast Iron Work - Dublin City Council
The Repair of Wrought and Cast Iron Work - Dublin City Council
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IRON THE REPAIR OF WROUGHT AND CAST IRONWORK<br />
3. <strong>The</strong> Deterioration <strong>and</strong> Decay <strong>of</strong> <strong>Iron</strong>work<br />
<strong>The</strong> deterioration <strong>of</strong> ironwork is caused by three factors:<br />
> Chemical corrosion (rusting)<br />
> Galvanic corrosion (also known as electrochemical<br />
or bi-metallic corrosion)<br />
> Mechanical action<br />
underside <strong>of</strong> rails where drops <strong>of</strong> water hang for<br />
long periods <strong>of</strong> time before falling away<br />
> Vegetation can trap <strong>and</strong> transfer moisture, <strong>and</strong> has<br />
the added disadvantage <strong>of</strong> hiding corrosion from<br />
view. Acids <strong>and</strong> chemicals in plants can also be<br />
harmful to ironwork <strong>and</strong> their growing roots <strong>and</strong><br />
tendrils can damage structures<br />
Additionally, more general factors that set up the<br />
conditions necessary for deterioration <strong>and</strong> damage<br />
include:<br />
> Inherent faults in the original manufacture<br />
> Lack <strong>of</strong> maintenance<br />
> Moisture<br />
> Poor workmanship<br />
> <strong>The</strong> use <strong>of</strong> substitute materials<br />
> Inappropriate alterations<br />
> Disuse, neglect <strong>and</strong> v<strong>and</strong>alism<br />
CHECKING FOR CORROSION<br />
When checking for corrosion pay particular attention<br />
to the following areas:<br />
> Water traps are vulnerable spots for corrosion to<br />
occur. <strong>The</strong>y are <strong>of</strong>ten caused by design flaws, particularly<br />
where hollow or cupped details are not<br />
filled, pr<strong>of</strong>iled, or pierced to shed water. Water traps<br />
can also be created by flaking paint or exp<strong>and</strong>ing<br />
rust<br />
> Water can seep into joints <strong>and</strong> so care should be<br />
taken to ensure that all joints are properly caulked<br />
(filled), either with traditional red lead paste or a<br />
polysulphide mastic. Traditionally, bolts <strong>and</strong> screw<br />
heads were caulked to protect them <strong>and</strong> to hide<br />
them from view<br />
> Masonry sockets can be vulnerable if lead holding<br />
the ironwork in place begins to break down. <strong>The</strong><br />
gudgeon (also known as the heel cup) <strong>of</strong> a gate is<br />
the hole that receives the foot <strong>of</strong> the gate which<br />
swivels as it opens <strong>and</strong> closes. This can be prone to<br />
corrosion as water tends to lodge there<br />
> Horizontal elements <strong>of</strong> ironwork tend to suffer more<br />
corrosion than other parts. This is because water<br />
<strong>of</strong>ten lies on the flat surface, or may drip continuously<br />
from above. Corrosion may even occur on the<br />
An oxide layer has developed on this wrought iron<br />
h<strong>and</strong>rail which protects it from further corrosion<br />
Broken, flaking paint traps <strong>and</strong> holds water to the<br />
iron, preventing it from drying out properly, <strong>and</strong> can<br />
lead to corrosion. Areas <strong>of</strong> chipped paint are not as<br />
significant a threat so long as the iron is in an<br />
exposed location <strong>and</strong> is able to dry out. Nevertheless,<br />
such chips should be treated as soon as possible to<br />
prevent rust from forming<br />
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