Although bronze bars and other
copper alloys are highly valued by artisans and architects for their decent
resistance against corrosion, they can still be subject to tarnishing and
discoloration. This is especially true for copper-based metals placed outdoors
and are constantly exposed. Common types of bronze like architectural bronze, commercial
bronze and statuary bronze, for instance, have particularly poor resistance
against some elements found naturally in urban settings. Under such conditions,
a bronze structure will deteriorate gradually over long periods of time.
If you want your
bronze craft to retain its distinctive appeal and hold up against corrosion,
you need to be aware of some environmental risks they could face. Be sure to
take precautions against these problems.
Urban Pollution
Heavily populated
cities have a high concentration of pollutants, especially sulfur
compounds, in the atmosphere. With continuous exposure, you can
expect bronze to corrode at higher rates. It usually begins with the appearance
of patches of light green on horizontal surfaces where rains and water run-off
flow through. Over time, the effect spreads over the entire surface, making the
metallic construction appear bright green instead of reddish gold.
Bird Droppings
Bird droppings,
as well as other animal droppings, are virtually unavoidable for fixed outdoor
structures. They not only obscure the appearance and message of your installation,
but they unfortunately also tend to be highly acidic in nature. When they
accumulate on the surface, they accelerate localized corrosion and
deterioration. The bronze will start to turn darker, and without applying
special cleaning procedures, the metal will eventually take on a light green
color.
Plant Debris
Decaying plant
debris such as leaves, cones, needles, twigs, bark, seeds and flowers may
create quite a beautiful scene during autumn, but they can cause considerable
damage to bronze. This is because the ammonia produced naturally when plants
die can darken the metal. In fact, ammonia in chemical form is used by many
metal workers to produce an artificial patination on copper, brass and bronze.
The good news is
that you can protect bronze statues or architectural structures by applying
coating systems and coating additives. Some great examples of basic coatings
include nitrocellulose, acrylic, epoxy, silicone, alkyd, urethane, cellulose
acetate butyrate, vinyl and polyvinyl fluoride film. Coating systems can make
bronze much more resilient against humidity, pollution, sunlight, abrasion, and
the regular wear and tear.
Note that
coatings differ in terms of resistance they offer against certain elements. It
is therefore ideal to ask suppliers, such as Rotax Metals, whether finishes
were already applied to the raw material. This way, you can determine if
applying coatings or additives to bronze is necessary. Remember as well that
protective coatings need to be reapplied once they wear off to preserve bronze.
About Rotax Metals
Founded by Ronald
Rosenthal in 1947, Rotax Metals is now a renowned supplier of high quality
copper, brass, and bronze products for a variety of industries. We offer an
extensive inventory as well as special services. As a family-owned business, we
make it our mission to provide great customer service while we assist you with
all your metal needs.
Sources:
Clear Organic
Finishes For Copper and Copper Alloys, Copper.org
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