Its a common misconception that SS does not rust. There are different types of SS with different corrosion resistant levels. Even the most higher resistant once corrode under specific conditions and exposure to certain chemicals like Hydrochloric and Sulphuric acids.
For example SS 303 is one of the worst SS in terms of corrosion resistance. 304 is good to great, 316/316L are excellent.
The main cause of corrosion is the Chloride ions commonly found in salts, which we have in the nutrients. That is the reason why you cant use 303/304 in marine applications as it will rust super fast.
316/316L contains 2% to 3% of molybdenum, a hard, silver white metallic element used to toughen steels and increase corrosion-resistance in nickel alloys.
I’m planning to use a mixed diluted nutrients solution (not a concentrated one) in AAA system. So it will not be as concentrated as a normal hydroponic solution, but may be 1/3 to 1/2 of a normal concentration that one would tipically use.
Found this: https://hayata.com/stainless-steel-chemical-resistance-chart-m-o/ - could be very useful for anyone that wants to compare the elements in the hydro solution against the corrosion chart.