Conservation problems in terms of metal sculptures generally result from reaction in metal due to atmosphere and environment. As metals are reactive with their environments, it is important to maintain safe and controlled storage and exhibition space. The environment of outdoor metal sculpture like bronze cannot be controlled. But it can be protected by a suitable surface coating. Metal sculptures may also suffer mechanical damage such as cracks or breaks, and they have to be repaired. Undesirable degradation or corrosion in metal artworks, due to environmental agents, should be prevented. Humidity and moisture are serious environmental hazard for metal works. In the presence of atmospheric humidity copper brass and bronze corrode, iron rusts and silver tarnishes more quickly. Most stable polished or painted materials can endure a humidity level of up to 55% RH, and they are not damaged. But lower level of humidity is preferable. On the other hand, corroded, unstable iron and bronze need an even drier environment. And the relative humidity in storage area of such art works should not be above 45%.
Metal artifacts become instable and damaged when salts that have come into metal objects during burial or exposure react with the metal and with water from the atmosphere. As a result, these reactions can disfigure and distort the image and surface. In time, they can lead to complete disintegration of the sculpture. Useful treatments for unstable iron and bronze have been developed. They consist of either the application of chemical moisture barriers to the metal surface or chemical removal of harmful salts. By reducing humidity as much as possible, these fragile materials can be stabilized against further degradation and damage. This is one of the simplest and most reliable ways.
It is very important to preserve the artist’s patination from a bronze sculpture on ethical, aesthetic and practical grounds. The same rules apply to some naturally acquired sculpture patinas. Such practices not only enhance an objects beauty but may preserve the form and details of the art works as much of the original metal has been changed by corrosion. Furthermore, some controlled and restrained cleaning and other surface treatments are quite useful in order to display metal sculptures to create best effect.