efflorescence

[esox247]

Hi all been preparing previously painted pebbledash (will have to try saying that down the pub after a few bevvies ) ready for first coat tommorow but in 3 small places it has been patched up with cement these areas had white powder over them, efflorescence me thinks! so i figure i need alkali resisting primer but is this ok outdoors as all the references i can find on here talk about it indoors

many thanks
esox

 

[JohnD]

All the pebledash will be alkaline, probably made with lime and cement. I expect the masonry paint you are using is used to it. Brush off what you can of the salts crystals. (I would have said use a wire brush, but if it's pebbledash you might knock the stones out).

Don't use water as you will wash the salts back into the wall and they'll come out later.

 

[esox247]

Nice one! Cheers for the advice john.

 

[Third_Eye]

Yep, it can be used externally