I think that besides potential faking-off and causing particulate problems, there could be some sort of galvanic-series issues to investigate.
I know that in the case of our turbines, zinc is to be avoided. Something to do with silver alloy in certain bearings and corrosion problems.
I'm not an expert in delivering a solid technical repsonse to your question.
However, from a practical side, your recommendation for carbon steel appears to be appropriate, since that is the primary material used in oil applications. Stainless steel might even be better if you are trying to combat a "wet oil" problem. I would assume this is why the vacuum dehydrator was added, unless you had a budget to work with and wanted to enhance your system(s).
I personally don't like galvanized piping for much of anything (Water or oil). Carbon steel, stainless steel, or copper tubing (where appropriate) are my materials of choice.
You might see some zinc or other strange things show up in oil analysis in the future with the galvanized pipe installed.
Be careful!!!
Good Luck.