Aloha,
SORRY- just saw this topic.
I don't get online everyday, so I can miss some things. It's to bad so many repeat topics are constantly being started. It would help everyone if we got the habit of replying to existing topics, as there are enough to cover any situation.
I see no corrosion with Robic, I use 1/8 tea. per gallon with one coil, 1/2 tea. with two in series. Some of the pics are with Robic.
304 is fine, I honestly don't agree with all the particularities with s.s. Get what you can, at the best price. Mine is always free. I just got two commercial restaurant refers free, that we are cutting up.
No noticeable changes switching polarity.
Watch your timing. You likely do not have to change it at all, unless you are making lots of hydrogen.
With a 1.5 motor, two cells in series, 1/2 tea. lye, full vacuum into intake will give you 20% or more increase in economy, in my experience.
Bill