Rust Versus Stain

Trouble-Shooting Stain Guide for Surgical Instruments

Stains can be removed, whereas rust will leave permanent damage. To determine if a brown or orange discoloration is a stain or rust, use the eraser test. Rub a pencil eraser over the discoloration. If the discoloration is removed with the eraser and the metal underneath is smooth and clean, this is a stain. If a pit mark appears under the discoloration, this is corrosion or rust.

Stain Color: 

Cause: 

 Brown / Orange  A result of high-pH detergents, Chlorhexidine usage, or improper soaking of instruments. This color stain can also be caused by soaking in tap water.
Dark Brown  Low-pH instrument solutions. The brownish-colored film may also be caused by a malfunctioning sterilizer. Similar localized stain spots can also be a result of baked-on blood.
Bluish Black Reverse plating, when instruments of different metal (e.g., chrome and stainless steel) are ultrasolically processed together. Additionally, exposure to saline, blood, or potassium chloride will cause this bluish black color.
Multicolor Excessive heat by a localized hot spot in the sterilizer. The rainbow colored stain can be removed.
Light & Dark Spots Water droplets drying on the instruments. With slow evaporation, the minerals sodium, calcium, and magnesium left behind can cause this spotting.
Bluish Gray Liquid (cold) sterilization solution sbeing used beyond manufacturer’s recommendations.
Black Contact with ammonia or a solution containing ammonia.
Gray A liquid rust remover being used in excess of manufacturer’s recommendations.
Rust Dried blood that has become baked on the serrated or hinged areas of surgical instruments. This organic material, once baked on, may appear dark in color. Also can be caused by soaking in tap water.


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