In general SS will not fail by general corrosion.
When it corrodes it is almost always localized pitting attack.
So there is no corrosion rate per se.
If you select the correct alloy then corrosion is Zero.
Adding thickness does not improve life with pitting failures.
In all of these cases you are better off with a welded system than a mechanically joined one.
Do not use threaded pipe, you will regret it.
When you weld you must ID purge so that there is no weld discoloration.
In 316L systems the welds are usually autogenous (no filler).
In 304L systems it varies.
-What concentration of caustic? What temp? what are the impurities?
While this isn't generally difficult with SS the details mater a lot.
-How clean is your demin water? Do you want to keep your demin water clean? If it is high purity and you want to keep it that way use 316L instead of 304.
-Is you diesel fuel clean? Is there any water in it, ever?
TBE can probably tell you horror stories about storing fuel and either getting salt water into it or biological growth.
This is one of those cases that you have to watch out for.
-Air. SS will usually hold up very well.
We used 316L for our entire plant air system (as well as pure N2, Ar, H2, and He).
We did have very dry plant air.
-Potable water is usually handled in 316L because of variations in chlorination.
There is world wide experience using 316L in distribution and well as domestic applications.
With all of these you need to think about the external surfaces also.
If you are near the sea coast (20km or so) you may need to paint the outside of the pipe to prevent external pitting.
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P.E. Metallurgy, consulting work welcomed
