On 8/8/07 12:26, in article ,
"Barb" wrote:

Nope, the Steradent didn't work, Mike. Worth a try though. Just went to
Halfords, in passing, and they didn't have anything.

Just tried some vinegar and a bit of elbow grease on one spot with a brush,
and it's shifted some of it, probably the stuff on the surface. And it's
left a nice really, really clean ring round it!!!! Can't win.

I might experiment with the vinegar over a wider area, actually. It's cheap
enough and not nasty.

Barb
snip

I can't think why I didn't think of this before! Here's the relevant
section from Cormaic's page with all the gen:

Removing rust stains
Rust stains arise from water running over metal fixtures and fittings then
depositing iron particles on the paving and/or from the oxidation (rusting)
of iron-rich compounds in the aggregate of the paving. There's also a danger
of accidental staining when weed- and mosskillers containing ferric sulphate
are applied to lawns and gardens next to paths, patios and driveways.
Rust stains are probably the most difficult to remove from most types of
paving. Many of the dyes used to colour concrete paving are based on iron
oxides, so many chemical agent may affect both the rust and the dyes. The
'patio cleaners' sold at the DIY sheds are based on a hydrochloric acid, and
these usually have no effect on rust, although the stronger acid dilutions
can sometimes make the stains darker.
Due to enormous differences in the type, nature and porosity of any
substrate, there are a number of possible 'solutions' that may work. It
should be noted that just because a particular 'solution' works well on, say
yorkstone flags, that does not mean that it will work on imported stone, or
on concrete flags. Similarly, any particular solution may have different
effects on wet-cast and pressed concrete flags. Whatever is used, it's best
to try it out in a small, discreet area first, as it's impossible to predict
just how any of these will react with any given stone or concrete.
€ Lemon Juice - genuine lemon juice, fresh from a lemon, not from a
bottle or a plastic imitation lemon. Squeeze directly onto the stained area,
allow it to react for 5 minutes or so but don't allow it to dry out. While
still wet, scrub the stained area with a nylon/polypropylene bristled brush
(an old toothbrush is ideal), working the lemon juice into the surface of
the paving. Wash off with plenty of clean water after 5 minutes and repeat
as necessary.
€
€ Vinegar - use a clear or white vinegar (spirt vinegar) rather than
a coloured vinegar (malt or balsamic). Some readers of this site have
reported that cider vinegar gives good results on some concrete surfaces.
Use in exactly the same way as described above.
€
€ Oxalic Acid - nasty stuff, as it's highly toxic, and it's not easy
to find. It's more commonly used in the woodworking trades to bleach or
whiten wood, but it is quite effective at removing heavier rust stains from
concrete and some types of stone. It may come as a proprietary "rust
remover" in which case you should follow the manufacturer's instructions to
the letter. The efficacy of these products is highly variable and they MUST
be tested on an inconspicuous area prior to use to ensure that the paving is
not damaged or discoloured by their use.
General purpose concrete cleaners may also help to remove rust stains, but
again, they are incredibly variable in effect, and it might be as well to
use just a simple detergent and hot water.
All this leaves mechanical action as the only non-chemical remedy; vigorous
scrubbing with a wire brush can sometimes remove the worst of the staining,
as can 'buffing', a process where a hard stone or abrasive is used to 'sand
down' the surface of the paving, removing the rust, and revealing a clean
surface beneath.
As ever, prevention is better than cure. Although rust staining does not
pose a threat to the structural integrity of the paving in the way that oils
do to tarmac, it can be unsightly and detract from the aesthetics. Removal
of rust sources and/or use of drip trays will keep most of the stains off
the pavement. If using a mosskiller, then ensure any adjacent concrete
surfaces are covered and protected.
http://www.pavingexpert.com/stains.htm

--
Sacha
http://www.hillhousenursery.co.uk
South Devon
(remove weeds from address)
'We do not inherit the earth from our ancestors, we borrow it from our
children.'