I agree with Fred. I always use a blend of these two dry acids, and a pinch of neutral cleaner as a surfactant, maybe 5% of muriatic and a 80 grit brush, pressure wash and it will be beautiful. I like Miricle Sealants 511 which will enhance a bit and is  comparable with slate. 

Sent from my iPhone

On 4 Mar 2015, at 8:36 pm, Fred Hueston <fhueston@gmail.com> wrote:

I would start with a good cleaning with a mild acid such as sulfamic. To attack the rust you can use some oxalic acid. be sure to rinse. I would not seal it. Not a big fan of sealing exterior stone..too many issues. Just selll them on maintenance

On Tue, Mar 3, 2015 at 10:45 PM, Randy Frye <rfrye@comcast.net> wrote:

Just a thought

http://www.drytreat.com/cleaners/regular/hanafinn-eff-erayza.html

> On Mar 3, 2015, at 6:58 PM, Justin <justin@jmcstoneandtilecare.com> wrote:
>
>
> I'm putting a estimate together for this slate patio and also around the pool. It's got combinations of efflorescence and rust stains. I'm looking for suggestions on a good aim of attack. They understand it wasn't the best choice but want to keep it maintained and sealed I'm hoping to get them on a maintenance program suggestions would be greatly appreciated.
> Thank you
> Justin
>
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> <IMG_1403.JPG><image1.JPG>
> Justin Cameron
> JMC Stone and Tile Care
> Justin@JMCStoneandTileCare.com
> 951-972-6997

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Frederick M. Hueston
www.stoneforensics.com

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