Sodium Sulphate: Pipeline Corrosion Inhibitor?

Well, sodium bisulphite is an oxygen scavenger. Does that help?

There's tons of stuff on these two materials in Wikipedia.

Sodium Sulphate is not used in isolation as a corrosion inhibitor. Sodium Sulphate along with Sodium Chloride or Sodium Phosphate can be used as corrosion inhibitors. But, you have to be careful, as imbalanced Sodium sulphate can lead to pitting inside pipeline if used alone.

Sodium chloride? Chlorides are usually the main component measurd to determine the corrosivity of a solution to attacking ferrous materials. Iron Chloride is highly soluble, would not expect it to form a thin layer and remain, similarly iron sulfate is fairly soluble, which leads to the pitting. Sodium Phosphate reacts to form a thin layer of metal phosphate, which is exceedingly insoluble, and thus a protective layer against corrosion. Bisulfite is a oxygen scavenger thus reducing potential for oxidation of the reduce metals. I would suspect a solution of Sulfate and Chloride would be about as bad a combination as you would want to see in a pipeline.

What you mentioned is logical. However, the studies show otherwise and the combination I mentioned is not uncommon for use in pipe lines.

Hmm, I'd like to see some of this research. As most corrosion inhibitors, such as various phosphates, are tested against chloride or chloride+sulfate. Addition of Chloride+Sulfate still seems less than preferable, but I would be interested in seeing these studies.