Bronze sculptures, renowned for their durability and artistic beauty, often face degradation over centuries due to various natural and human-induced factors. Understanding these causes helps in preserving these invaluable artifacts for future generations.

1. Environmental Exposure: Bronze sculptures exposed to outdoor elements suffer from rain, humidity, and pollutants. Acid rain, in particular, accelerates corrosion by reacting with the metal, leading to surface pitting and loss of detail.

2. Oxidation and Patina Formation: While a natural patina (greenish layer) can protect bronze, excessive oxidation weakens the structure. Chlorides and sulfides in the air react with copper in bronze, causing irreversible damage over time.

3. Biological Growth: Lichens, moss, and microorganisms thrive on moist bronze surfaces, secreting acids that erode the metal. This biological activity is especially harmful in humid climates.

4. Improper Handling and Maintenance: Human touch, cleaning with harsh chemicals, or incorrect restoration techniques can strip protective layers, exposing the bronze to further degradation.

5. Pollution and Industrial Contaminants: Urban environments with high levels of sulfur dioxide and carbon monoxide accelerate bronze corrosion, leading to discoloration and structural weakness.

By addressing these factors through controlled environments, regular maintenance, and advanced conservation techniques, the longevity of bronze sculptures can be significantly extended.