What Causes Rust Spots in the Dishwasher on Stainless Steel Silverware?

Stainless steel is not always stain free or rust proof, particularly when the stainless steel is flatware for the American home. Stainless flatware must endure acidic foods, prolonged soaking, dishwasher temperatures and strong detergents. The composition of stainless steel determines the likelihood for rust. Care for your quality stainless flatware, and it will last a lifetime.

Sauce pans
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Stainless steel pots.

Quality

Close-up of a fork
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Close up of stainless steel fork.

The quality of your stainless steel makes a difference in the way it reacts to dishwasher use over time. Stainless steel flatware is made of steel, chromium and nickel, and the composition is on the original box or on the backs of the utensils. The Nickel Institute reports that 10 percent or more chromium is essential to rust avoidance. Stainless steel marked 18/10 or 18/8 is 18 percent chromium and 8 or 10 percent nickel, both metals that help protect from rusting, reports the Silver Superstore website. Stainless steel marked 18/0 has no nickel content and may rust more easily. Stainless steel knives are often made of 13/0 or 13 percent chrome and are the most likely utensils to rust. The box may also indicate that the stainless steel is type 304 or S30400, the most common grade of stainless for use in the home.

Foods

Mayonnaise
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Mayonnaise can stain.

Mayonnaise, vinegar, coffee and tea, mustard and eggs left on stainless steel may cause corrosion on stainless steel flatware. Minerals in the tap water may also affect the surface, according to the Oneida website. Do not leave stainless steel flatware in contact with these foods to help prevent rust and corrosion. Soaking flatware overnight may add to corrosion.

Dishwasher Detergent

Tablets for dish-washing machine
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Dishwasher detergent.

Use of lemon or orange citrus dishwasher detergents can cause corrosion on stainless flatware, the Oneida website suggests. Oneida recommends powder dishwasher detergent that is not highly chlorinated. Do not pour dishwasher detergent so that it gets onto stainless steel, warns the Flatware.org website. Changing detergents to find one compatible with the tap water may improve stainless steel flatware results.

Care for Stainless Steel

Dishwasher contents
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Utensils in the dishwasher.

Care for flatware to avoid rust and corrosion. The hot air dry at the end of the dishwasher cycle is not good for stainless steel flatware. Oneida recommends removing stainless steel after the last rinse cycle and drying with a soft cloth. White vinegar is a suitable cleaner for stainless steel according to the University of Arkansas Cooperative Extension Service, but rinse the flatware after cleaning. Oneida suggests using stainless steel cleaner followed by rinsing.