Typhus Corrosion vs Primer Black

How close are they?

ΔE 31.5, loose: different enough that you should pick on purpose. Primer Black is noticeably darker, much more muted than Typhus Corrosion.

Can I use Primer Black instead of Typhus Corrosion?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 31). Primer Black is noticeably darker, much more muted than Typhus Corrosion.

Can I use Typhus Corrosion instead of Primer Black?

The same difference applies the other way round: Typhus Corrosion 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.