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I've owned a lot of stainless steel knives and tools of other kinds. I've never had any of them rust. I recently bought a set of stainless steel knives and the blades get rust spots every time they're cleaned.

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In this image, there are spots scattered around the blade (rust and blemishes from previous rust spots), but the significant new rust is next to the handle, along the bottom edge in the unserrated portion towards the handle, and on the top edge above the end of "Dynamic".

These knives happen to be steak knives (and the use they get is cutting food, then they're washed in a dishwasher). My question is on the metal, since the same metal can be used in tools used in crafting. Henkels is a reputable brand; I doubt they would make knives from carbon steel and label them stainless steel. And for comparison of usage, I've always used stainless steel eating utensils that get the same usage and cleaning, and none of them has ever rusted.

So I assume there is something different about the grade of stainless steel that is used in these knives, and some grades are prone to rusting like carbon steel. Obviously, people can't do metallurgical tests on a picture to identify the metal. I assume that characteristics like rust-proneness of various types/grades of stainless steel are known. Perhaps people might even be familiar with what type of stainless steel Henkels uses in their knives (through their own testing; Henkels doesn't release that information).

A lot of tools are made of stainless steel, and they get used with wet materials and water cleanup. Tools that rust like this example could require rust removal before use with many art/crafting materials to avoid contamination, discoloring, or other problems. When buying tools, is there a way to identify whatever this type of stainless steel is, by sight (some visible characteristic or manufacturer information stamped on it), or by asking the manufacturer about a spec, so I can avoid buying tools made from the same stuff?

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  • When they go in the dishwasher, are they touching anything else? Especially anything else metal, but also things that can hold water against them. I put my sharp knives in the dishwasher, but without other metal in the same compartment of the cutlery basket, to avoid the blade getting chipped against hard things. I've had a very few rust spots
    – Chris H
    Dec 7, 2022 at 16:05
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    @ChrisH, you're thinking maybe there's some electrolytic action going on with dissimilar metals? Great thought, but not in this case. I no longer wash them in the dishwasher, but when I did, each knife was in a separate divider. The rusting stood out because I have never gotten rust on any other SS utensils with identical treatment, indicating the metal in these is different. It's possible that the rack held some water on the knives, but they're the only ones that ever rusted from it (and there was rust on every knife every time).
    – fixer1234
    Dec 7, 2022 at 17:48
  • It was worth considering - but you already had by the sounds of things.
    – Chris H
    Dec 7, 2022 at 20:44

1 Answer 1

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What causes stainless steel to rust is salt and water. So, if washed and dried it should not rust. I agree Henkels has a good reputation and seems unlikely to use carbon steel. However there are many alloys used in "stainless" cutlery. Most are about 13 % chrome. Alloys with a minimum of 5% Cr are considered stainless, these would be resistant to rust but not as good as 13 % Cr but better than carbon steel.

No obvious answer. Possibly the cause is something very unusual like a faulty dish washer cycle or brackish water. Maybe Henkels will tell you the alloy they use. A commercial analysis will cost more that the knives. Maybe you know someone with access to a XRF portable element analyzer, they have become common and relatively inexpensive.

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  • Henkels says the information is proprietary (maybe because there isn't any Cr in it?). A few other people complained online about Henkels knives rusting. Nothing unusual with the water or detergent, and the dishwasher isn't faulty. The knives stand out because the dishwasher is full of cheap stainless steel cutlery and nothing else rusts. It appears that the stainless steel in the Henkels knives just rusts way more easily than any other stainless steel I've encountered. If I had one of those analyzers, I could take it with me when I shop for tools. :-)
    – fixer1234
    Nov 13, 2022 at 1:43
  • If we assume the problem is low Cr, is there a beneficial reason Henkels might use that other than because it's cheaper or maybe easier on their equipment? Like would low Cr SS have better characteristics for knives (e.g., hold an edge longer, be easier to sharpen, or some such reason)?
    – fixer1234
    Nov 14, 2022 at 7:07
  • If other people complained too, then maybe Henkels is not anymore what it used to be (I've never heard of them). On the positive side, rust is not only NOT toxic to the human body, but actually beneficial (in trace quantities). As long as the knife is clean, you can safely use it for food, even if there are rust spots. The discussion would be different if we would talk about rust scales instead of rust spots.
    – virolino
    Nov 14, 2022 at 14:08

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