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After just 2 days of using my new carbon steel wok pan, I noticed something suspicious inside it:

Burnt oil?

Looking back on it, it was probably just burnt oil and nothing to worry about. However, I mistook it for rust, and began my arduous journey to get rid of it. (Let me know what you think it was and what to think of it in the future, please)

First I scoured the spots with water and plastic scouring wool, then added some dishwashing liquid and continued the process, but it had practically no effect on the spots even after tens of minutes of work. Eventually I just chose to nuke the pan and start the seasoning process all over again.

I decided to try soaking the pan in acid and filled it up with water, adding some grams of citric acid into the mix. After some 20 minutes of waiting and haphazard scrubbing, the inside of the pan looked shiny enough for me even though there were still some bits of crud left. I removed the acidic solution and, just to be safe, filled the pan with water and some grams of baking soda in order to neutralize the acid. (Looking back, I do not think this was enough)

After that, following the guidance of numerous internet guides (e.g. 1, 2), I wanted to temper the wok again. I assumed that the protective oxide layer formed while bluing the pan for the first time had been erased along with the rest of the seasoning.

However, after I had blued the pan and waited a couple of minutes for it to cool down, a horrible sight awaited me:

Flash rust?

I am almost certain that this was rust—the infamous flash rust.

I was petrified. Too demotivated to start the process all over again, I tried to season the pan, hoping that the "rust" was just a harmless byproduct of the bluing process. (Though I had not seen it when tempering the pan earlier)

This ended just about as well as anyone could expect:

...

I had clearly botched the seasoning. In hindsight, I think I may have tried to polymerize the thin coat of rapeseed oil over heat too high.

Thus, my main problem is as follows: how do I prevent flash rust from appearing after tempering the pan? I quite clearly cannot just rub oil on it to protect it while it's at 350 degrees celsius (≈660°F)... Do I just have to cool it down really quickly with water? Also, what caused it? Acid residue?

In general, how should I proceed? Can I, or should I, even repeat the bluing process again while reseasoning the pan? How acidic should the initial nuking solution be; is more acid better, or less?

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  • Er, given that the pan is new, why does it have so many scratches? (this may be relevant to your rust problem)
    – FuzzyChef
    Jul 31 at 3:44
  • @FuzzyChef The scratches came to be due to the plastic scouring pad that I used—it has a sharp metallic head meant for removing particularly sticky pieces of crud. Initially I was wary of using it, but I had read that scratches don't really matter when it comes to carbon steel pans and went ahead with it. It's the best I have available as of right now.
    – Otso
    Jul 31 at 13:16
  • 1
    Unfortunately, scratches do matter, particularly when you're trying to fight rust.
    – FuzzyChef
    Jul 31 at 18:44
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Your first picture might be the beginnings of a seasoning layer, though a bit lumpy & uneven from poor technique.
"it was probably just burnt oil and nothing to worry about" - yeah… but that's what you actually want. That's the seasoning, or the very beginnings of it.
In the later photos, I see no evidence of any seasoning remaining… nor, in fact much blueing. Personally, I think the blueing* is a waste of time so long as you make sure to get rid of any industrial oil from the surface before you season it. I'm sure the thrashing you've given it will have done that. What's left is an unseasoned pan that will rust if you so much as look at it askance.

It's the seasoning that prevents rust. You can scour it all you like, but until you get a proper polymer coat on there it will just keep rusting again. Seasoning is not oil - it's what oil turns into after heating to a high temperature for a long time, almost a plastic; a polymerised coating. The first layer or two will look yellowish to brownish [but not red like rust]. The more layers you get on it, the further towards black it will go. Many very, very thin layers are far better than one thick layer, which will just peel or chip off.

Neither of those links gives me much confidence, tbh. Try What's the best way to season a cast iron skillet? instead, & just do it upside down in the oven, 5 or 6 times… once you've got the rust off again.

*heating mild steel until it goes blue isn't really 'blueing', which is a chemical process, it's case-hardening - similar to what a swordsmith would do. It has two purposes, to harden & to resist rusting. Unless done properly it actually achieves neither.
By far the best way to protect an iron pan or wok is to season it. Do it properly, use it often & you'll never need to do it again.

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  • After I had initially tempered and "seasoned" the pan, it looked like this from afar. Thus, I of course assumed that the rather dark new color of the pan was the seasoning and the orangeish spots were but an anomaly. Well, you learn something new every day. I will give your advice a try and report back! (As you can see from the photo, my pan has wooden handles and it cannot be placed in the oven. I will just try to heat it under lower heat this time.)
    – Otso
    Jul 31 at 13:25
  • Don't use lower heat, you need it as hot as you can get it, but you need oil on it, as thin as you can get. Your earlier photo looks like you managed to case-harden it [which is the bit I've never bothered with in 40 years;) but shows no real signs of seasoning - I'd have expected the rivets to get seasoned too; it's hard to really tell on the dark surface, but it looks way too blue-black for that to be a good coating of seasoning.
    – unlisted
    Jul 31 at 14:44
  • A more reliable way to season any iron pan is to heat it to 500F/250C (or slightly hotter) and then rub it with oil on a paper towel or cloth rag. You're going for a very thin coat, like 0.1mm, the thinnest coat you can get. Then you let it cool, then heat it up and do it again 2-3 times. Pouring or spraying oil gets too much oil and you get gummy blobs.
    – FuzzyChef
    Jul 31 at 18:46
  • @FuzzyChef After nuking the pan once again with acid (this time for longer—that clearly helped) it took me about 3 hours to achieve this look. (I think I took that pic after washing it though) I probably applied a new coating of oil some 30 times. Perhaps the scratches made it more time-consuming ¯_(ツ)_/¯Do you reckon I should blacken it more or just trust that the uneven seasoning will get better with time? I did try to fry an egg with a smallish to moderate amount of oil and it stuck to the pan like crazy.
    – Otso
    Aug 9 at 22:29
  • That honestly looks like a pretty good coating to start with. But ... if an egg is sticking, that's the real test. FWIW, if I get my wok hot (400F) then eggs don't stick at all. I can easily scramble in the bottom of it. Maybe open a new question?
    – FuzzyChef
    Aug 9 at 23:24

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