tarnishes

Tarnish is a dull or discolored film that forms on metal surfaces as a result of chemical reactions with substances in the environment, such as oxygen, sulfur compounds, or chlorides. It is usually a superficial layer created by oxidation or sulfidation and can often be removed to restore the metal’s original luster.

Different metals tarnish in characteristic ways. Silver tarnishes when exposed to sulfur compounds, forming silver sulfide that appears black. Copper and copper alloys commonly develop copper oxide or copper sulfide, producing a range of colors from brown to red to green patina. Aluminum tends to form a thin, protective layer of aluminum oxide that dulls the surface but can slow further deterioration. Precious metals like gold and platinum are highly resistant to tarnish, while chromium and stainless steel form stable oxide layers.

Tarnish is generally reversible through cleaning, polishing, or chemical cleaners designed for the specific metal. In some cases, a patina may be purposefully developed for aesthetic or protective reasons. Preventive measures include storing metals in low-humidity environments, using anti-tarnish packaging or coatings, and avoiding exposure to sulfur- or chloride-containing substances. Regular maintenance can extend the visual appeal of metal objects.

Tarnish differs from corrosion in that it is typically a surface phenomenon that does not always compromise structural integrity, whereas corrosion can involve deeper, more damaging material loss. Some patinas are stable and long-lasting, while others are easily removed to restore appearance.