Suitable primer for exterior concrete prior to painting?

[dpm_dpmartin]

I have a building with external concrete bits that require a repaint. I use Sandtex Ultra Smooth Masonry Paint to match.

I am not sure whether it's been done with a primer before. I've certainly not used a primer when I've touched-up areas. I doubt the previous owners did to be honest. This is possibly why I keep needing to touch-up areas (maybe, it is outside after all).

I'd like to prepare the surfaces properly, but I'm confused as to what primer I should purchase.

It's not a garage floor I'm talking about... and it's not totally bare concrete, as I say, there's paint on there already, but I'm looking to at least sand it down to, hopefully, create a good surface for a new coat, then prime, then paint with matching Sandtex.

I gather there's about lots(!) of primers I could choose - does anyone have any recommendation as to type and even specific product? I won't blame you if it goes wrong, but I don't know whether an acrylic primer, polyurethane primer, epoxy primer or silane sealer is the way to go...

Any thoughts as to what you may have used in the past, with good results, would be very welcome.

I am also having an area of concrete repaired, so that will then end up being bare, new, fresh concrete - and I will need to paint that properly.

 

[Robbie uk]

Any bare concrete, render etc will only need a thinned down coat of what ever your putting on to act as a primer. Then coat up with more full coats. If its flaking anywhere, scrape it off and apply a coat of stabilising solution to the affected areas prior to coating up with full coats. Do not use PVA or Silicon paints!

 

[Chri5]

I've used this on salted previously painted external walls with are flakey.

Use a flapper wheel in a grinder to remive the flakes, then coat with primer and then paint. First job I did 5 plus years ago still looks really solid.

http://www.screwfix.com/p/mapei-pla...tracking url&gclid=CNWAl4j2zc4CFRPjGwodFtcBfw

 

[misterhelpful]

What Robbie uk said.

Also, ensure the new concrete/render is thoroughly dried out before painting.