Rust vs. Stain

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.

Trouble-Shooting Stain Guide for Surgical Instruments

Stain Color: Brown/Orange

Cause:    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.

Stain Color: Dark Brown

Cause:    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.

Stain Color: Bluish Black

Cause:    Reverse plating, when instruments of different metal (e.g., chrome and stainless steel) are ultrasonically processed together.  Additionally, exposure to saline, blood, or potassium chloride will cause this bluish black color.

Stain Color: Multicolor

Cause:    Excessive heat by a localized hot spot in the sterilizer.  The rainbow-colored stain can be removed.

Stain Color: Light- and Dark-Colored Spots

Cause:    Water droplets drying on the instruments.  With slow evaporation, the minerals sodium, calcium, and magnesium left behind can cause this spotting.

Stain Color: Bluish Gray

Cause:    Liquid (cold) sterilization solutions being used beyond manufacturer's recommendations.

Stain Color: Black Stains

Cause:    Contact with ammonia or a solution containing ammonia.

Stain Color: Gray

Cause:    A liquid rust remover being used in excess of manufacturer's recommendations.

Stain Color: Rust

Cause:    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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