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.
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, 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.
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