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This is a simple question, although I don't have any exact numbers.

I was looking to buy a food-safe stainless steel sieve, and one of the reviewers showed the sieve they purchased heavily rusted and "punctured" after testing it in "hydrogen peroxide with salt as a catalyst", claiming it thus cannot be 304 stainless steel as stated by the seller.

I don't know what salt concentration that person used (let's assume >1%) and for how long was the piece submerged (probably no longer than several hours), but from what I read online – while it should be hydrogen peroxide-resistant, 304 stainless steel is not considered salt-resistant.

So considering a sieve's large relative surface area, plus the presence of salt (whose corrosive function is augmented by the hydrogen peroxide or not?), is it safe to presume the reviewer did not use a suitable test to claim the material is not 304 stainless steel?

The photos provided by the reviewer

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  • $\begingroup$ related chemistry.stackexchange.com/questions/139905/… $\endgroup$
    – Mithoron
    Commented Oct 25, 2022 at 14:13
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    $\begingroup$ Of course it's not a suitable test? To tell what a material is you need to test for composition, structure. People are imagining that stainless steel cannot corrode - they are wrong. $\endgroup$
    – Mithoron
    Commented Oct 25, 2022 at 14:15
  • $\begingroup$ @mithoron I'm not saying that this test could equate to a molecular level of testing, but as a general assessment how incompatible are the results for 304 stainless steel verification? The salt alone, unless used in huge amounts, probably shouldn't corrode that much that quickly, but I wondered if combined with the hydrogen peroxide it does create a more prominent corrosion effect that's expected to dissolve a sieve very quickly. Also related, several reviewers mentioned it is quite magnetic, unlike 304, but I know 304 is usually slightly paramagnetic so could the threaded form increase that? $\endgroup$
    – TLSO
    Commented Oct 25, 2022 at 14:38
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    $\begingroup$ Go to a nice, local kitchen products store. Buy a good sieve. If it rusts, return it. $\endgroup$
    – Jon Custer
    Commented Oct 25, 2022 at 17:03
  • $\begingroup$ @joncuster I need something with a very fine mesh in order to smoothen liquid solutions, and all those available locally seem to have the regular >1mm holes. $\endgroup$
    – TLSO
    Commented Oct 25, 2022 at 22:28

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Depends on specifics. The bulk of food processing facilities are 316 and 304. The 316 and 317 are more resistant to pitting but the equipment is cleaned and dried on various schedules. All these alloys will rust exposed to salts. I am unaware of many higher alloys being used for food as in the chemical industries but I have no direct experience in food industry. PS : a magnet will indicate the austenitic stainless like 304 and 316.

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  • $\begingroup$ I understand they are more or less salt rusting-prone, but the issue is whether the extreme rusting and dissolving demonstrated in the reviewer's images could be due to the hydrogen peroxide reacting with the rust. Because otherwise, even if the solution had several dozen % of salt, how quickly should a 304 sieve dissolve? Also regarding (para)magnetism, I did mention in a comment a couple of reviews said it was uncharacteristically magnetic, but the sieve is probably made of drawn wires and it is written this could induce paramagnetism. $\endgroup$
    – TLSO
    Commented Oct 25, 2022 at 22:33
  • $\begingroup$ The austenitics are not ferromagnetic when annealed ( 316 may show a trace). They become increasingly ferromagnetic as they are cold worked/strain hardened. It is very difficult for me to imagine 304 dissolving in salts at ambient temperatures. $\endgroup$
    – blacksmith37
    Commented Oct 26, 2022 at 15:58
  • $\begingroup$ The drawing process is a colf working one, no? The question is whether the high surface area of a sieve + the presence of hydrogen peroxide (I read it interacts with rust, but I'm not sure if it's true for 304) could cause quick dissolving. $\endgroup$
    – TLSO
    Commented Oct 26, 2022 at 16:19
  • $\begingroup$ Small particles may dissolve , but I am expecting a sieve to be about 1 mm thick ; it would only have surface rust. $\endgroup$
    – blacksmith37
    Commented Oct 26, 2022 at 19:38
  • $\begingroup$ Well, I've added the pictures added to that review, if that provides any information. I found several videos demonstrating instant rusting using hydrogen peroxide, salt and an acid of sort, but I didn't find a video demonstrating the effect without an acid. $\endgroup$
    – TLSO
    Commented Oct 26, 2022 at 19:59

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