Preparing Concrete for Paint.

[CYWALL]

Hi everyone,
the underside of our bedroom balcony is in desperate need of re painting, it's all flaking off and looks really scruffy.
It's been on there for around ten years so can't complain.
However I'm looking for some advice on what to treat the underside/concrete with before I commence painting,
assuming it should be treated first.
Any advice would be gratefully accepted.
Thanks for reading.

[WHL]

Go to someone like orinos/ DIY store, and get a stabilizer , give the wall a coat of that then paint.

[Mighty Sprite]

a 50/20 mix of PVA and water

So what is the rest of it?

[Aargent]

Surely if it is a ratio, rather than a percentage, there is no more. Percentage was not mentioned in DB's first post.