The fact is you never clean copper awnings. The beauty of copper is formed by a green patina that naturally occurs on its own. However, it can be chemically enhanced to quickly generate the patina. Additionally, with the right protection, it can be treated to never develop a patina. To develop a quality patina on any item made out of copper requires exposure to the elements. If you prefer that it never develops its own patina, it is essential not to clean the copper unit with any harsh chemicals that might strip away the protective coating.
Environmental Conditions Can Oxidize Copper
When copper is exposed directly to the environment, it causes a natural reaction with oxygen. However, the reaction can take place when moisture, condensation, rain, or water allows oxygen to be dissolved during direct contact with the metal. Traditionally, copper will exhibit optimal resistance to corrosion in marine, urban, and industrial environments. Any major aspect that will control the initial rate of environmental attack on copper will cause it to turn green. This can include pollution, temperature, and moisture.
A Natural Reaction to Oxidize
Once copper has been exposed to the atmosphere, it quickly begins to oxidize. The once bright, shiny surface will quickly take on a duller, tarnished-tan appearance. Within a few years, the once shiny copper will quickly turn to a dark brown or black. During the later stages of corrosion, the copper will turn green. This is a result of the formation of copper sulfate, chloride salt, and carbonate in various concentrations.
Naturally developing the formation of green patina of copper roofs, cupolas, copper awnings, and gutters often takes years. However, there are several effective methods that have been developed that can produce identical results through artificial means, using specific reactions of chemicals to the metal.
Optimal Resistance to Corrosion
It has been shown that copper displays good resistance to corrosion when in contact with a variety of elements including fresh water. The corrosion rate of copper when in contact with water saturation, which includes carbon dioxide and air, tends to be of a greater magnitude than the corrosion rates of contact with distilled water. When around seawater, copper has also been shown to have good resistance. It is often used to protect surfaces that are directly exposed to seawater. Patina on copper is a naturally produced layer that develops to protect the copper underneath. Whether it develops a patina on its own, the patina is chemically induced, or the reaction has been chemically halted, copper lasts for decades outdoors, virtually maintenance free.