Patinization

Patinization is the process by which a surface develops a patina—a thin, durable film of corrosion products, mineral deposits, or surface oxides. Patinas form naturally through exposure to air, moisture, and pollutants, or can be produced intentionally to achieve an aged appearance or to protect underlying material. The resulting color and texture vary with material and environment.

On metals, patination commonly involves copper alloys and iron. Copper and bronze forms verdigris or green-blue layers; iron develops brown to black oxides. Patinas can be several micrometers to tens of micrometers thick and may slow further corrosion by limiting access of water and aggressive species to the metal surface.

Artificial patination is used in art, architecture, and artifact conservation to create a controlled, desirable finish. Techniques include chemical baths that promote specific oxides or sulfates, heat patination to create oxide layers with color changes, and the application of organic or inorganic coatings to stabilize the patina or modify sheen. Process control is important to prevent pitting or overly thick layers.

In conservation and archaeology, patina is sometimes considered part of the object's authenticity; researchers may prefer stabilizing existing patina rather than removing it. Patination can also be used intentionally in replicas to imitate antique surfaces, though ethical standards vary by field.

Care and handling of patinated surfaces depend on the material and patina composition; harsh cleaners can damage the patina. When restoration is involved, professionals aim to preserve or reproduce the patina and may apply protective coatings to balance appearance and durability.