Strange black spots on cockpit non-slip sole

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BelleSerene

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Over the past few months my cockpit sole has developed strange tiny black marks, which tend to sit in the tiny valleys of the non-slip texture. They won't wash away with deck cleaner and a sponge, but you can scratch them away with a sharp knife. Of course, I don't want to damage the sole by lots of sharp scratching. If you told me it was some fungal infection I'd believe you.

Does anyone know what it is and how to treat it please? Here's a photo. (Yes, this is a grubby bit of the cockpit - the boat's in London and she attracts grime like a magnet at the moment - but it's those black specks that I'm concerned about, and they won't go away.)

View attachment 62166
 
BelleSerene said:
Over the past few months my cockpit sole has developed strange tiny black marks, which tend to sit in the tiny valleys of the non-slip texture. They won't wash away with deck cleaner and a sponge, but you can scratch them away with a sharp knife. Of course, I don't want to damage the sole by lots of sharp scratching. If you told me it was some fungal infection I'd believe you.

Does anyone know what it is and how to treat it please? Here's a photo. (Yes, this is a grubby bit of the cockpit - the boat's in London and she attracts grime like a magnet at the moment - but it's those black specks that I'm concerned about, and they won't go away.)
Click to expand...

Mould or Mildew ? If so Patio Magic or Polycell 3in 1 Mould killer will kill it but it may take a while to get rid of the black spots.

If that's a GRP surface then some diluted domestic bleach, or a bleach based mould killer ( eg HG mould killer from B&Q or Dettol Mould & Mildew Remover), will also kill it.
 
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BelleSerene said:
Over the past few months my cockpit sole has developed strange tiny black marks, which tend to sit in the tiny valleys of the non-slip texture. They won't wash away with deck cleaner and a sponge, but you can scratch them away with a sharp knife. Of course, I don't want to damage the sole by lots of sharp scratching. If you told me it was some fungal infection I'd believe you.

Does anyone know what it is and how to treat it please? Here's a photo. (Yes, this is a grubby bit of the cockpit - the boat's in London and she attracts grime like a magnet at the moment - but it's those black specks that I'm concerned about, and they won't go away.)

View attachment 62166
Click to expand...
Next step up in boat cleaning chemical warfare would be Gif bath cleaner cream plus a stiff toothbrush.

Given the city location could it be some tar fallout deposit? Does a dab of petrol on a cloth lift the marks?

After that we are talking organic oxidizer.
 
jonjo5 said:
Next step up in boat cleaning chemical warfare would be Gif bath cleaner cream plus a stiff toothbrush.

Given the city location could it be some tar fallout deposit? Does a dab of petrol on a cloth lift the marks?

After that we are talking organic oxidizer.
Click to expand...

Thanks. The problem arose over months in Hamble. The City location is just temporary as she's in London for a couple of months. Accounts for the general grime but not that black-spot phenomenon.
 
BelleSerene said:
Thanks. The problem arose over months in Hamble. The City location is just temporary as she's in London for a couple of months. Accounts for the general grime but not that black-spot phenomenon.
Click to expand...

I'm on the Hamble and I've seen similar. I put it down to being downwind of Fawley oil refinery - oily deposits. I doubt it is fungal.

It should come off with a good scrub.
 
Although it looks a bit like mould, I've not had this on GRP. We occasionally get muck from Harwich and I don't think London is the cleanest place on the planet. I would try some white spirit on some and see if this removes it.
 
Angele said:
I'm on the Hamble and I've seen similar. I put it down to being downwind of Fawley oil refinery - oily deposits. I doubt it is fungal.

It should come off with a good scrub.
Click to expand...

You might be right. If the power station was still operating I'd have suggested smuts from there but I would have wanted them under a microscope to look for coked oil droplets.

Theres an awful lot of them to be fallout from the refinery ( or the powerstation)
 
johnalison said:
Although it looks a bit like mould, I've not had this on GRP. We occasionally get muck from Harwich and I don't think London is the cleanest place on the planet. I would try some white spirit on some and see if this removes it.
Click to expand...

Fantasie 19 said:
+1
Click to expand...

The OP has said, " The problem arose over months in Hamble. The City location is just temporary as she's in London for a couple of months. Accounts for the general grime but not that black-spot phenomenon."
 
To expand on what I said before, I had exactly what you describe and it was some kind of mould. One boat was out in the country away from any close source of pollution. I know other owners who had the same thing. I bought another boat from down Solent way, that had the same thing. In all cases, Patio Magic got rid of it. Easily.
 
I'm on the Hamble too and get the black spots. Scrubbing never seemed to do it so I tried with a pressure washer and it comes off beautifully
 
I too am on the Hamble and this is a regular appearance on my and other yachts- right up to the Swanwick marinas,where Moodys used to reside. Pressure washing will get them off, but you need to go alongside for the mains power to do that. Does not occur so much in the summer months but maybe because the boat is used more then, or Fawley not so busy.

ianat182
 
I get the same thing on Kiwi Deck, you can pick it out with a toothpick, but that's rather tedious! As others have said, a pressure washer is the answer but don't use more power than you have to; I bought the smallest Karcher just for this job.
 
I have the same problem. When I scratch it and rinse with water the 'run off' goes a dark green. Patio magic will be used later in the year as the pressure washer didn't really touch it last year.
 
Thanks to all. I tried some diluted Patio Magic on it, left it for a week and it was still pretty immovable. I tried with some 'Starbright instant hull cleaner' (an oxalic acid product), diluted, and with a good scrub I got the stuff off the cockpit sole.

I honestly don't know which product it was. Perhaps I should have diluted the Patio Magic less.

But anyway, thanks to all. Now for some patches of non-slip on the coachroof and the decks. Perhaps I'll try Patio Magic on one side and hull cleaner on the other to find out what the effective chemical is!
 
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