Definition - What does Controlled Atmosphere mean?
A controlled atmosphere is an environment that is artificially produced, in which the oxygen, nitrogen and carbon dioxide concentrations as well as the temperature and humidity are regulated.
Corrosion rates are directly influenced by the atmospheric conditions. In uncontrolled atmospheric conditions, the corrosion rate increases because there is an imbalance in the constituents of the atmosphere (e.g., sometimes high temperature, high humidity, etc.).
Corrosionpedia explains Controlled Atmosphere
Atmospheric conditions can cause corrosion and erosion of metals and nonmetals. Earth's natural environment of oxygen and condensed water vapor is itself sufficient to cause the gradual corrosion of iron and steel surfaces, producing iron oxide (rust).
The vital factor that causes corrosion in the uncontrolled atmosphere is the presence of moisture due to fog, dew, precipitation and relative humidity. In a completely dry atmosphere, oxygen and carbon dioxide do not cause corrosion. Salts of sulfur and chlorine can aggravate corrosion by forming electrolytes in industrial atmospheres. Ambient temperature and air pressure also affect corrosion. At higher temperatures some electrolytes become highly reactive.
The corrosion rates can be manipulated in controlled atmospheric conditions for testing or specific production requirements.