Definition - What does Bronze Disease mean?
Bronze disease is the permanent and almost unstoppable corrosion process that takes place when chlorides react with bronze or other alloys containing copper. It appears as a fuzzy green or dark green coating present on bronze, copper and other copper-bearing alloys.
It can be due to salt water contamination or a result of being buried in dirt, since soil contains chloride salts at a certain degree. If it is not treated, total deterioration of the infected material is most likely. The transport of chloride from a contaminated object to other objects could spread this form of corrosion.
Corrosionpedia explains Bronze Disease
Signs that a material is experiencing bronze disease include powdery, light green or brown spots or growth on bronze. It is a type of active corrosion, which means that the item is not protected and is constantly corroding, leading to severe damage.
Bronze disease is produced by the following reactions:
- Copper undergoes oxidation to cuprous ion.
- Cuprous ion forms a reaction with chloride ion to produce salt cuprous chloride.
- The residual copper undergoes oxidation through air to cuprous ion.
- Cuprous ion reacts with chloride ion to form salt cuprous oxide.
- The reaction repeats, which results in fuzzy green spots or appearance.
- Cuprous chloride reacts with oxygen and atmospheric moisture to form hydrochloric acid, hydroxide compound and cupric chloride.
Bronze disease can be controlled through surface treatments and cleaning, such as using sodium sesquicarbonate. If the chloride ions have penetrated beyond the metal surface, internal treatment is required. Waxes that are capable of binding to the surface can also be used to prevent bronze disease from occurring.