For example 316 series are more resistant to environments (eg. underwater) with higher concentrations of Chlorine while 304 series are less resistant.
The other thing I would worry about in a acidic environment is pitting which wouldn't show up if you test the intact plate. Basically your steel backup will have letters "chiseled" on it which is a localized defect and in an acidic environment it could cause pitting which would increase the speed of corrosion.
My question is, do you think it's resistant in an environment with nitrogen (N), and/or potassium oxide (K2O)?
I'm not good at chemistry but these two have no effect on corrosion. I've seen potassium hydroxide be used as an etchant though (which is a solution we use in crystallography to selectively corrode part of the structure so that it can be viewed and analyzed).I then had a quick search (and clicked the first result 
) and found https://link.springer.com/article/10.1016/S1006-706X(10)60090-8.
That's about the existing nitrogen atoms in stainless steel that may be desorbed (removed) from the alloy while it is in a molten state in above 1550 °C which could affect the properties of SS such as its hardness. ) and found https://link.springer.com/article/10.1016/S1006-706X(10)60090-8.It is not about corrosion
