Red Ecstasy vs Corrosion

How close are they?

ΔE 59.2, loose: different enough that you should pick on purpose. Corrosion is noticeably darker, much more muted than Red Ecstasy.

Can I use Corrosion instead of Red Ecstasy?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 59). Corrosion is noticeably darker, much more muted than Red Ecstasy.

Can I use Red Ecstasy instead of Corrosion?

The same difference applies the other way round: Red Ecstasy is noticeably lighter, much more saturated.

ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.