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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
- Cast Iron
- Wrought Iron
- Mild Steel
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.