Nature has painted my decks green - how to reverse .......... ??

[NormanS]

I mixed oxalic acid with wallpaper paste.

 

[Steve_N]

Any benzalkonium chloride based mould and mildew or patio cleaner will do the job effortlessly
eg
Patio Magic , which is widely available
Wet & Forget, from Screwfix and Robert Dyas etc
Barrenttine Knockout Mould and Mildew Cleaner, from Toolstation

Good for killing algae on ropes etc
AFAIK safe on hoods and covers etc but always test on a corner if in doubt.

As VicS says the active ingredient in all these cleaners is the same and at approximately the same concentration (7.5 - 9% typically), making W&F by far the most expensive way of buying benzalkonium chloride.
Cheapest by a good margin over these named cleaner cleaner products is 'BAC50' (available on ebay and elsewhere) at 50% concentration.

A quick price search online and a back of fag packet calculation gives the following approximate prices per litre of active ingredient:
- Wet & Forget £75/litre
- BAC50 £12.40/litre

I've been using BAC50 diluted accordingly for years on both boat and motorhome, sometimes even the patio, and it works as expected.

 

[jwilson]

Personally I won't let a jetwasher near my GRP decks, and using one on teak is a hanging, drawing and quartering offence. Moulded non-slip patterns on GRP decks are almost inevitably resin-rich, so more brittle than a flat moulding like your hull, and jetwashers can knock bits of GRP off. They are also remarkably good at finding (possibly by creating) deck leaks around windows/hatches etc.

Patio Magic or other benzalkonium chloride based product followed by local oxalic acid for rust stains. Then after each works hose off with a softish brush.

 

[Shaz77]

Personally I won't let a jetwasher near my GRP decks, and using one on teak is a hanging, drawing and quartering offence. Moulded non-slip patterns on GRP decks are almost inevitably resin-rich, so more brittle than a flat moulding like your hull, and jetwashers can knock bits of GRP off. They are also remarkably good at finding (possibly by creating) deck leaks around windows/hatches etc.

Patio Magic or other benzalkonium chloride based product followed by local oxalic acid for rust stains. Then after each works hose off with a softish brush.

There has been talk of industrial jet washes of very high pressure and osmosis.

 

[PabloPicasso]

Be careful with jetwashers. They can remove sealant around deck fixings, which in turn, allows moisture into cored decks.

Not what you want.

Patio magic and a deck brush is easy, gives good results, and won't do any damage.

Stops the green returning for a good length of time too

 

[PabloPicasso]

I mixed oxalic acid with wallpaper paste.

What type of wallpaper did you hang?

 

[lustyd]

Oxalic acid or an oxalic acid based cleaner such as Y10 will remove those.
.

Grunt, mentioned at the top of the thread is perfect for this. Premixed as a paste that stays put. We recently used it on our waterline while afloat and it’s by far the best product we’ve ever used.

 

[lustyd]

Thanks, it says its a regulated poison but available for business use, and not that expensive for 1 kilo. Cheers

Marine Bazaar in Plymouth sell it, as do some fibreglass suppliers.

Grunt is far easier to get and easier to use though, and no need to get wallpaper paste as it’s premixed

 

[RunAgroundHard]

Once you have cleaned the deck, regular dowsing with sea water will keep the green mould away. Rain and freshwater washing will not stop green mould.

 

[Slowtack]

Sorry ….. it is GRP …… I have never used patio magic - small areas only or the whole thing ??

Seawater...

 

[NormanS]

Once you have cleaned the deck, regular dowsing with sea water will keep the green mould away. Rain and freshwater washing will not stop green mould.

Yes, we only get the green, and plenty of it, when ashore for the winter. Dirt and mud at any time.

 

[Momac]

I do use patio magic and the like but I found it damages the windows on the canopy so I no linger use it on the boat.
I do have a jet washer but I don't use that on the boat and do not feel a need for it.

I use a snow foam type detergent in water and find that quite effective .

A little citric acid can help remove stains from GRP and wood

 

[dunedin]

Coincidentally put on some Patio Magic today after a nice sail.
Took a few minutes to apply, then go away and the green magically disappears before next visit.
PS. I am happy to use on the sprayhood etc but avoid getting on windows, or wipe off if any runs. No issues so far and been using on teak decks for nearly 20 years.

 

[Goldie]

I am thinking the following (it is pretty bad) ...........

1. Jetwash

2. Scrub using Ecover washing up liquid.

3. On stubborn areas, use oxalic acid/Y10

4. Jetwash again.

Does anyone have any better suggestion ? ............ many thanks

Sodium hypochlorite, as used for cleaning swimming pools and the like. We use it on north facing whitewashed walls which go green in winter and I’ve seen it used on grp with good results.

Dilute at approx 5:1, apply (I spray, but with mask, gloves and goggles) go for a coffee, come back, hose off job done .

 

[MoodySabre]

Yes, Patio Magic works brilliantly, on decks and canvas alike.
Personally I to brush on rather than spray on, my be wrong but feels less risk.

I brush it too.

 

[ducked]

I brush it too.

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