On Monday, 24 July 2017 15:17:34 UTC+1, wrote:
My workshop floor has been power floated and I believe I need to etch
the surface before painting. Is this just a case of wetting it, brushing
on some hydrochloric acid, and then hosing it out after about 20 minutes?
How can I estimate the amount of acid for 30 m2 floor area?
How do I know when it's sufficiently etched?

The main thing to be aware of is to be sure there is a damp proof membrane beneath the concrete.
If not,forget it, the paint will flake off due to trapped rising damp.