Why Is There Rust on My Stainless?

Dear Home-Ec 101,

My very nice, very expensive stainless steel Mikasa silverware is picking up rust spots. I know it’s not rusting, because it’s stainless, and the spots appear to be surface. How do I get rid of  the rust spots on my flatware? I’m so tired of them looking icky, it happens to my good knives too. Could it be coming from my dishwasher?

Signed,
Rusting in Rutherford

Heather says:

I’m going to let you in on a secret. There’s a reason stainless steel is called stain LESS and not stain FREE. The stainless steel we see so often in our homes is corrosion resistant, not corrosion proof.

Let’s start by thinking about what steel is. Steel is an alloy – not too get into too many details, a blend, if you will- of iron and usually carbon. When the steel cools, the carbon atoms fit into the lattice / matrix structure of the iron atoms and give it slightly different properties. Sometimes other elements are used in addition or instead of carbon, with stainless it’s chromium and sometimes nickel. The exact blend is what determines its susceptibility to rust.

What you are seeing on your flatware is a tiny bit of surface rust. It’s pretty harmless, but my old standby – Bar Keepers Friend – is a great solution. Just follow the directions on the can.

Never try to remove the surface rust with steel wool, you’re just going to exacerbate the problem. At first it will look better, but given time the problem will be back and look much worse. If you must use an abrasive, use something like a Scotch Brite pad and only rub with direction of the brushing.

Now, keep in mind that stainless steel is different from the carbon steel you’ll find used to make some knives. I highly recommend you stay away from carbon steel. Check out this post on how to sharpen your knives for the full explanation.

Send your questions to helpme@home-ec101.com

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Comments

  1. says

    I used to work in the metal industry, and a lot of people don't know that stainless steel can be contaminated by carbon steel. If stainless touches regular carbon steel, the iron molecules from the carbon steel can rub off or adhere to the stainless's surface and that's what's rusting. You're right that it's on the surface and not throughout the piece. Stainless steel is an alloy (in expensive flatware, it's an 18/10 alloy of iron, chromium, and nickel) and the "contamination" just sits on the surface.

    Cast iron, iron woks, grills, carbon steel knives, or steel wool are all common items in the kitchen that can contaminate your stainless merely by touching it.

    In the industry we'd use acid cleaners to get rid of the rust. You can also use a grinder or dremel fitted with a NEW stainless brush or flapper that hasn't touched carbon steel to remove it (go with the 'grain' of the stainless (that's an industrial solution- I'd try a product made for the home firs!) DEFINITELY do not use steel wool!

    • says

      Very interesting. Seems I remember my mother telling me once not to put the knives (carbon steel) next to the silverware. Why had I forgotten that? lol

      K, so my BK friend comes out this evening, and I'm polishing away those nasty spots. Then I'm going to keep my flatware separate….

      Thank you both for the awesome tips!
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  2. jackindigo says

    To add to this, I have stainless steel piers under my house from a company called RamJack. But they rusted immediately. I complained, and the response I got back was, "You have to understand — there are two kinds of stainless steel. The kind for silverware, and the kind that rusts a protective patina on the outside. Of course, the kind for silverware would cost everyone a fortune for steel pier construction, so we use the kind with the protective rust patina. Do not worry — your piers will last you more than a century."

  3. says

    There's actually 3 main kinds of stainless steel but the third kind is a specialty product. Your piers are probably ferritic stainless (flatware, appliances, sinks, etc. are austenitic stainless). Flatware is 18/10 (18% chromium, 10% nickel) and the other all purpose stainless is usually type 304. Another FYI- if you are renovating your kitchen you can save a ton of money by skipping the home improvement/decorating stores and going to a metal distributor and getting 304 sheets (specifiy brushed finish) instead.

  4. Keter Magick says

    Brasso removes rust and has just enough acid to remove the carbon steel contamination. Don't let it sit, though, wash thoroughly after you are done. Some stainless – particularly stainless sinks – will discolor with dark spots after exposure to acid. (Milehimama might know why; I bow to her metallurgical alpha-geekitude.)

    BTW, one source of potential carbon steel contamination that you might not think of is the common copper mesh scrubber, which are decreasingly made of copper; they are mild steel with a copper overlay, and rust like mad.

  5. says

    Most household acids (i.e., vinegar, etc.) won't discolor stainless steel, it takes a pretty heavy duty acid to do that. However, the chromium content in it creates a coating or patina of chromium oxide and chlorine can remove it, as can too much abrasion/rubbing. Where do you find chlorine in the kitchen? Heavily chlorinated water ,table salt, or bleach (BTW- Cascade contains bleach!) Brief contact won't mess things up, but over time if it sits on the surface for a while it can cause corrosion. (So, don't brine your turkeys in your stainless steel sink.)

    Also, if ammonia gets mixed with a very strong acid it can corrode, but I doubt that's what's happening to your sink (unless you clean with nitric acid and Windex… in which case, sink stains are the least of your worries!)

  6. says

    And within these comments is just another reason I love Home Ec 101. Heather has not only built a great resource, but seemingly has managed to pull together one fabulous community, where no matter the topic, there is always somebody that has some great new knowledge to share with the rest of us.

    Thanks Milehimama for teaching me more than I ever thought I would care to know about steel., It has explained a lot of issues that have vexed me over the years.
    My recent post Home Ec-101- Skills for Everyday Living Review and Giveaway

  7. says

    Stain-LESS has nothing to do with "less stains". It really does mean it shouldn't ever stain (unless contaminated as described in the other comment). Think of the suffix -less as meaning the same as the French prefix sans-, e.g. sans-culottes.

    • Tim says

      "Stainless" steel is a general classification of steels that have a high chromium content. Nickel, molybdenum, niobium, and titanium are sometimes also added to aid in corrosion resistance depending on which grade of steel is being produced. 420,440C,ATS-34, S30V, CPM T440V, and 8cr14mov are just a few types of stainless steel used in knife production.
      Gavin, all steel (yes, even "stainless") is susceptible stains, rust, and corrosion (that's chemistry for you)… albeit at different rates depending on composition.