The Brew Cabin

On clearing the winter debris off my garden last weekend I noticed that there were a number of green stains on my newly build patio - ARGGGHHH!!!!!

They are all under the table and chairs which I purchased as they were advertised as being suitable to leave outside in all weathers. The only source for these stains that I can identify are the zinc galavanised stainless steel nails and bolts used in the furniture - but I thought these were supposedly corrosion resistant? I contacted the manufacturer but apparently they have not had this problem before!

The slabs are dyed concrete riven slabs and initial attempts at cleaning the stains had no effect. Have you seen this before and if so is there anything you can think of that might shift them?

In terms of prevention, do you think replacing the galvanised fittings with identical brass ones might help?

When I've seen 'staining' from galvanised items in the past, the 'stain' has been a light grey in colour, not green, which suggests a copper contamination or possibly a paint/dye. Technically, the light grey patches that are seen with some galavanised materials are not a stain, but a residue, and it usually washes away with a bit of scrubbing.

Hydrochloric acid or brick/patio cleaners would affect the flags and probably do nowt with the stain you describe but it might be worth a try, in a discreet corner. Have you tried the usual 'safe' options of hot, soapy water and/or a power washer?

Hi Tony,

Thanks for the quick reply. I tried hot soapy water but it had very little effect on it. I also thought that the green colour might have indictaed the presence of copper - I suppose it's possible that this batch of fittings might have been contaminated or something when they were galvanised.

I have thought of getting a power washer - there's a Bosch one which has a pulse jet which is apparently good for washing patios - but they're pricey.

Do you think a mild bleach solution would be safe or worth a go? I've a spare slab or two I could try out first!

You can hire a power washer for a day or a weekend from any decent hire centre. If you've a lot of paving, or you're one of those folk that likes to wash the car, the caravan, the kids' bikes etc each weekend, then a power washer can be a good investment, but for a one-off job, then hiring-in is the best route. It allows you to see if the stain will shift without splashing out (no pun intended) a big wad of dosh, only to find the damned spot will not out.

You could try bleach, or even a patio cleaner, but it's essential to test them out in a discreet corner, or on one of your spare flags, as some coloured concrete pavers can suffer a bad reaction to some cleaning products.

Hi Nigel

If all else fails try Resiblocks Patio Magic cleaner. Ive used it to shift alot of stains on patios in the past. You can get it from the Builders Center and if not in stock they will order it.

I like the reply from the furniture suppliers that they have never had that problem before..Sounds familiar.!!!

Kris......