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What
is Bronze?
Bronze is an alloy that contains mostly copper, tin and some lead .
It’s introduction over 5,000 years ago revolutionized metal work and
launched the Bronze Age. By adding tin to copper, workers created a
metal that was stronger and impervious to corrosion. Bronze artifacts
have been found dating from as early as 3,500 BC.
How is Bronze
gate hardware different from Brass gate
hardware?
Brass is also an alloy of copper, but differs from bronze in that its
primary additive is zinc instead of tin. Brass is similar to bronze in
hardness but suffers from the process of ‘dezincification’. This
process that begins upon exposure to heat and humidity is the leaching
of zinc from the metal. As the zinc migrates from the copper it leaves
a porous structure susceptible to cracking and corrosion. As a result,
brass hardware may eventually exhibit persistent red spots (zinc oxide)
and become more brittle and crack as they age.
Brass is commonly used for door hardware because
the melting temperature is lower than bronze making it easier to cast
in an automated production. The high melting point of bronze
necessitates casting in sand (a more difficult process) since the metal
molds used in brass production would melt. A new sand mold is created
for every individual casted part for Coastal Bronze.
Understanding Why Corrosion Happens
Corrosion of door hardware and gate
hardware occurs through several mechanisms that
are electrochemical in nature. In other words, chemicals react with the
metals to produce an electric current. This current changes the
structure and composition of the metal and results in pitting, flaking,
chipping and cracking.
The following chart illustrates how various metals found in door and
gate hardware compare in their resistance to corrosion:
Least Subject to Corrosion
- Stainless Steel
- Bronze
- Copper
- Brass
- Cast Iron
- Wrought Iron
- Mild Steel
- Aluminum
Most Subject to Corrosion
It should also be noted that while stainless steel is more resistant to
corrosion than bronze, it may be more susceptible at its edges, creases
and at points where it contacts other metals.
In an attempt to prevent corrosion, manufacturers use various coatings
(e.g. powder-coat, paint and sealers) on the more susceptible metals.
These coatings invariably fail to prevent corrosion since even
microscopic gaps or inconsistencies in the coatings expose metal. This
provides points of corrosion that can rapidly grow. The result is that
the coatings are undermined, separating them from the surface leading
to cracking and chipping.
Is Bronze gate hardware
more Beautiful?
Moving from the scientific to the aesthetic, we can assess the
superiority of bronze as a feature in the landscape. Bronze has a long
history of use as the preferred material for outdoor gate hardware,
partly because of its durability but mainly because it weathers so
beautifully.
Once installed outdoors, the metallic bronze
gate hardware darkens to an old-penny brown then
eventually to a greenish/blue patina. These colors compliment the
browns and greens in nature and do not distract from the natural beauty
of the landscape.
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