The steel type 1.4571 / (X6CrNiMoTi17-12-2, ASTM: more or less 316Ti) is commonly used in wastewater applications due to it's good corrosion resistance. An alternative is 1.4404 / (X2CrNiMo17-12-2, ASTM: 316L), which is often said to be inferior. Several steel plants published information materials to the following effect (don't have an english source, so I summarize the key points):
Heat treatment of carbon steels would lead to the formation of Chrome-Carbides, these are attack angles for corrosion. Ni and Ti are added to form 1.4571 because these elements form carbides and so prevent the formation of Chrome-Carbides.
Current (since a few decades ...) manufacturing technology allows lower carbon content in steel production, so that addition of Ni & Ti are no longer neccessary to have corrosion resistance as good or better as 1.4571 in many cases.
1.4571 is clearly superior in applications with T > 350°C
All information about the comparative corrosion resistance of these steels I found so far comes from steel plants and traders who have a vested interest in pushing 1.4404: 1.4571 is commonly used in Germany, Austria and some eastern European countries, apparantly the rest of the world moved on to 1.4404 et. al. This means german steel traders need to warehouse two types of steel.
Is, according to an independent assessment, the corrosion resistance of 1.4404 same or better than 1.4571 in most conditions?