Sodium Methlyate Material of Construction

The one that the suppliers of this material recommend on their Materials Safety Data Sheet, because they may decline to supply if the storage facility isn't up to scratch. After all, it is their reputation that is at stake.

Go grab the phone, and make the call.

This question makes it sound like you're into biodiesel. If that's the case, what you need to be asking is "What is the preferred material of construction for storing a liquid solution of 30% sodium methylate in anhydrous methanol"?

The general answer to that would be stainless steel- 304 is adequate, regular or L- for temperature up to the 65 C commonly encountered in these processes (as this is close to the boiling point of methanol you would now have much more important venting & pressure rating & relief concerns ). This is what would be most commonly used in industry, both biodiesel & chemical manufacturing. Cast iron is also a suitable material if trace contamination by iron is not a problem. Avoid any soft metals (aluminum, galvanized etc.) like the plague as the alkalinity will attack it & you could have serious leakage of what is essentially a highly toxic and flammable form of Caustic Soda.

Home brew biodiesel systems usually seem to use HDPE roto-molded tanks. These should be considered according to the compatibility of the SM solvent (since it can't be water!) and the expected storage temperature & pressure characteristics. Anything more will require you to post more info about your process & intentions.

Yes we are into biodiesel. My basic question should be, do we need to upgrade from carbon steel to 304L. Our supplier Evonik uses carbon steel at their manufacturing plant.

If there are no problems with catalyst impairment from any material pickup from the tanks (which can include flash rusting at +2 & +3 oxidation levels from atmospheric exposure due to level variations) then no. This is not your OP though, so cast iron or carbon steel should be fine from a point of structural compatability but may not be from a process point of view.

PS. Are you currently running? What is your crude glycerine disposal- I am working on a couple of projects that it is a optional raw material for.