Wok patina comes off I got a flat-bottomed iron wok a few weeks ago at a local Asian supermarket. I seasoned it on my electric stove, based on information I googled up: heated it up, put a thin layer of peanut oil on it, turned the heat down and let it sit for 15 minutes. This worked pretty well and formed a nice dark layer, but even after cooking in the wok a couple of times, I thought the seasoning could be better, so I decided to start over.

I used soap and a sponge scourer to get most of the patina off. To get more off, vinegar seemed like a good idea, so I boiled vinegar and water in the wok for about five minutes, let it cool, and scraped most of the remaining patina off. The wok looked (almost) good as new, so I dried it and proceeded to re-season it.

I applied my original seasoning procedure, which went well, but then the trouble started. I rinsed out the wok with hot water and rubbed it with a kitchen towel. In the center (where the metal gets the hottest, presumably), some of the patina stuck to the towel, and left iron-colored spots. I tried again twice, but the problem remained.

I thought maybe cooking in the wok would build up some patina, so I stir-fried some vegetables. Then, I rinsed and wiped it, and unfortunately, black flakes came off again. I can't seem to keep the entire bottom covered in patina.

So, any thoughts? Did I ruin my wok? Did the vinegar maybe form an oil-resistant layer or something? Anything I can try, or should I just get a new wok? Thanks.
You have overcooked the seasoning. I have done this once or twice too. Especially smooth surfaces (e.g. carbon steel) are very prone to this problem, unlike rough cast iron. 

What you want is not a dark layer. The layer will darken with time and start looking like usual. But on a freshly seasoned metal utensil, the layer should be yellow-brownish. The stove may be too hot for this, especially a gas stove, I do my pans in the oven, for maybe an hour at 200 Celsius or somewhat lower. A burner under thin metal can cause hot spots of much higher local temperature, where the oil chars instead of polymerising. 

There is also the type of oil you use. Generally, unsaturated oils polymerise easiest, but the final layer stays somewhat sticky. Saturated fat can give you some more trouble, but will have a smoother finish. I do multiple layers, starting with 1-2 layers of flaxseed oil - this gives a good basis, it is so unsaturated it can practically dry out by itself in the air - and finishing with cocos fat or lard, again 1 or 2 layers. For the first few time in a new pan, I try to fry with saturated fat too, for your wok you will probably find that the taste of cocos fat has a good harmony with Asian dishes. 

And a word to the cleaning before: Vinegar was not such a good idea. Woks are made from reactive metals (that's why they need seasoning) and metals react with acid. Using acid to clean naked reactive metal will result in invisibly small pockets of reaction products on the surface of the wok, mostly rust. You can do this as an early step in cleaning, but afterwards you have to use something to make sure you have removed this too. To peel off the seasoning before reseasoning, you are much better off using a base, as it does not react with the metal. This will ensure that the new seasoning sticks to the metal itself and not to impurities which can be dislodged over time.