not worried about the chlorine on stainless?
It's free chlorine that's the concern, and even then only when it gets above ~25 ppm. In alkaline solution the chlorine remains bound - I want to say the threshold is ~11 pH, but I can't recall offhand. As long as the caustic is mixed appropriately and not allowed to dry on the surface, and there's no residual beer or CO2
to acidify it, there's no risk of pitting.