On Sat, 01 Nov 2003 11:29:23 -0800, Koz wrote:
The caustic acts as a protectant of some sort and prevents
corrosion rathern than causing corrosion as stated (on mild steel).

What we said was that using caustic soda, or baking soda, or any
other alkali metal base to *neutralize* HCl remaining on the steel
from an acid dip produces a salt (in this case NaCl, table salt).
Unless the water is very hot, some of that salt residue will settle
in any pores, cracks, threads, or other feature of the part. *That*
will promote corrosion of the steel.

Obviously, if there is no HCl present, for example your potato
conveyor, adding caustic to the water does not produce salt,
and thus doesn't leave a residue on the steel which promotes
corrosion.

In combination with the starch in the potatos, caustic *should*
produce a carbonate scale on the metal which will in fact offer
some protection from rusting. But scale is what the original
poster is trying to remove, he wants bright metal ready for
galvanizing. So caustic is not advised.

Gary