Thanks to this forum, learned a lot about water, which unfortunately pulled me down to a new rabbit hole

Anyways, I ended up liking this custom water recipe:
20 GH - Epsom Salt concentrate
50 KH - Baking Soda Concentrate
RO Water as the base

Above recipe seems to be scaling resistant based on some research within the forum.
Does above recipe likely to cause corrosion?
How high can GH be before corrosion is likely (from sulfate Epsom)?

Found somewhere that Sulfates (from epsom salt) are slightly corrosion inducing, although less than chlorides (which hopefully RO system reduced significantly).

coolguy121 wrote:20 GH - Epsom Salt concentrate
50 KH - Baking Soda Concentrate

Your 20 mg/L as CaCO3 of magnesium sulfate works out to only 19 mg/L of sulfate ion. Not enough in my opinion to worry about.

There is no hard cuttoff where sulfate starts/stops being a corrosion factor, but where you have good alkalinity I don't think you need to worry at levels even two or three times what you have here. Chloride is a lot worse than sulfate, especially for brass and copper, and the most conservative advice about avoiding chloride is from Synesso, who use 15 mg/L as the level where chloride ion is worth special treatment consideration.

The cautious advice here is that if the Epsom does not noticeably improve your espresso's taste, then just don't add it. The rpavlis water that many people use in espresso equipment has 50 mg/L KH and zero GH.