MoxVib

Q: I have lots of stainless steel in my kitchen: the sink, refrigerator, dishwasher door, pots and pans. But a lot of it is stained and dull — even my Oneida teaspoons, which I have had for more than 40 years. How do I make the metal look shiny and new?

A: It’s easy to think of stainless steel as stain-proof because it is one of the most durable materials used in kitchens. But the word actually reveals the truth: It stains less — but that doesn’t mean the risk is zero.

Luckily, because the protection against rust and stains is built into the nature of stainless steel, the trick to restoring a like-new look is to strip away the corrosion or stains on the surface to reveal the stainless steel immediately underneath. Usually only a microscopically thin layer needs to go.

Stainless steel is an alloy, or mixture, of iron, chromium and other metals that vary depending on the type of stainless steel. Chromium, which needs to comprise at least 10.5 percent of the mixture for the alloy to be considered stainless steel, protects the iron from rusting. Chromium atoms at the surface readily combine with oxygen in the air or water and form a layer that blocks other oxygen atoms from combining with the steel and forming rust. When that layer is compromised, removing it allows the stainless steel to self-heal by forming a new chromium oxide layer.

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There are more than 100 types of stainless steel. Manufacturers select the type to use based on cost and the characteristics that their products need. Each grade has a three-digit number: first to identify its broad category; second, the specific alloy within that category; third, the carbon content.

Flatware, many kitchen appliances and sinks are usually 304 stainless steel, which contains 18 to 20 percent chromium and 8 to 10 percent nickel. The nickel is what makes the metal look silvery and lustrous, so small differences in that percentage can be significant. Oneida, for example, uses 18 percent chromium in all its flatware, but the nickel content varies, with Fine Flatware styles using 10 percent and Everyday styles, just 8 percent. Knife blades need to hold an edge, so they are often made with a different alloy that is stiffer but not as corrosion-resistant, which is why blades often show signs of rust or discoloration when the rest of the flatware looks fine.

Although Type 304 alloys are protected against rust, they remain susceptible to corrosion caused by salt and other chemicals, including bleach. To protect against that, 316 stainless steel, which also contains molybdenum, is better. High-end cookware and stainless steel appliances that will be used outdoors are often 316 stainless steel.

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It’s not necessary to identify the specific type of stainless steel to figure out how to restore its like-new look, but knowing there is great variety in the formulas helps explain why some surfaces stay looking good with little care while others get dull — and why it makes sense to test a small area before you try a new cleaning routine.

Spoons, forks and knives can become dull if food scraps, especially ones with salt or acids, are left on for long periods or if they are left to soak in water overnight. A stainless steel sink can rust if a cast iron pan (made of iron without rust-preventing additives) or silverware with salty food scraps is left in the sink to soak. Cleaning products containing bleach can also dull sinks because chlorine eats away at the chromium oxide layer, leaving iron in the metal susceptible to corrosion. And don’t use steel wool because bits can break off, become embedded in the fine grooves left from polishing the stainless steel at the factory, and rust.

To restore dull or rusted stainless steel, try scrubbing with a paste made of water and baking soda, a mild abrasive that will help remove the compromised chromium oxide layer so that a new protective layer can form. Or use Bar Keepers Friend or Zud, bleach-free scrub powders that contain oxalic acid, which helps remove the chromium oxide layer with less scrubbing.

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Here are tips for cleaning specific surfaces:

· For sinks, the Bar Keepers Friend website suggests dampening the surface, sprinkling on the powder, and rubbing in the direction of the grain. (These are the fine lines left from polishing the metal at the factory; in a sink, they usually go in a circular direction, following the outline of the bowl and drain.)

The website warns not to leave the powder on the sink for more than one minute before rinsing with warm water, and says that it’s okay to repeat the process, using more elbow grease. Why the one-minute limit? Jeffrey Hicks, the brand’s vice president for research development and a chemist by profession, said it’s a caution because sinks, especially lower-cost imported models, are sometimes made with less desirable stainless steel alloys.

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The time limit is “just to make sure it’s not going to react with the metal in a bad way,” he said. “Some alloys are not as good as others.” If left too long on stainless steel with low corrosion resistance, the oxalic acid can make the metal dull and gray. “It usually takes longer than a minute, so we say one minute.”

· Pots and pans, even imports, are usually made with stainless steel that’s reliably stain-resistant, Hicks said. So the advice is slightly different: Make a paste of the powder and water, apply it with a clean cloth, wait no more than one minute, then scrub in a circular direction. Rinse and repeat as needed. The Bar Keepers Friend website shows before and after pictures of the main problems that occur with stainless steel cookware: scorch marks and burnt-on food.

· For spoons, forks or knives that look dull and stained, Oneida’s website recommends using “a quality metal polish” to remove discoloration. But a customer-service agent for Oneida said the updated advice is to use Bar Keepers Friend or Soft Scrub.

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· Cleaning refrigerator and dishwasher doors is different because these often have a clear coating over the stainless steel. It’s designed to make fingerprints less noticeable, so you don’t want to scrub it off in an attempt to make fingerprints disappear. The bits of food that fingers can leave are easy enough to wipe away with warm or soapy water. But fingerprints are also oily and getting that off is more problematic.

One solution is to fight oil with oil — a bit of mineral oil will dissolve the oil in the fingerprints and allow you to buff the surface with a clean paper towel or cloth, going in the grain direction (which is usually crosswise on doors). But that leaves a light oily coating, making the surface a magnet for dust.

Hicks said he spent years developing Bar Keepers Friend Stainless Steel Cleaner & Polish, which is formulated to work well on appliances, regardless of whether the stainless steel is bare or coated. It has no oxalic acid but instead contains mineral oil in a water emulsion, plus a polymer that stays slightly soft and moldable even when it’s dry and shiny. Just spray it on and rub in the grain direction with a paper towel or cloth, Hicks said. Then, if someone leaves new fingerprints, you can just rub and the film will reform to make the fingerprints disappear.

Have a problem in your home? Send questions to localliving@washpost.com. Put “How To” in the subject line, tell us where you live and try to include a photo.

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