spotty decks

[muscey]

We are currently in NW Spain in the middle of an extended cruise, having left UK a few weeks ago. Since leaving we have noticed a rapid build up of what appear to be v small (pin prick-sized), rust coloured spots on the decks. They are mostly located towards the foredeck, although are also on the sides and on the coachroof. The deck is GRP, the boat is 1972 (decks probably original), and there was no evidence of these spots before we left Falmouth.

They are impossible to remove with hard scrubbing and detergent, and we haven´t used any unusual cleaning materials. They seem to be thriving on their new diet of sun and salt, and are multiplying by the day, and we havent got a clue what is causing them!

Has anyone got any idea about what might be causing this unwelcome spotty rash, and how we might be able to remove it? Any advice much appreciated.

Nick

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[johna]

I would look for something ferrous in the fore triangle area. Shackle, bolt, nut or even tieing wire on or about the forestay, baby stay, roller reefing, pulpit, anchor mounts. Also look at the cross trees. Your extended cruising has allowed some extended chafing.

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[charles_reed]

Steel filings from chafe, probably the forestay tang.

Oxalic acid will remove the spots but I'd be more concerned about losing my rig.

Have you any slack in the rigging?

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[philip_stevens]

Has a steel boat been anywhere in your vicinity while in Falmouth, and using an angle grinder?? Or someone cutting steel with an angle grinder on the pontoon?

This was how rust spots got on my GRP decks while laid-up. A moron with a steel boat decided to remove a part of it with an angle grinder. My decks were in the firing line!! It took a long time to remove the spots.

As Charles says, use oxalic acid or a GRP cleaner with dilute sulphuric acid in it - as in B&Q Patio Cleaner (I know you are in Spain, but they may have something like that there), or any cleaner to remove rust stains.

Before you get more postings on the sulphuric acid bit, it is the main ingredient in a bottle of GRP cleaner gel I bought in Aussie made by KH Industries - Aussies will verify.

<hr width=100% size=1>regards,
Philip

 

[Drummond]

Have you tried to clean any stainless steel with a metal pot scourer?

We did last summer and before long the decks were covered in rust spots.

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[jfkal]

Must be rust, either from your own hardware or someone elses. Try Vitamin C. Buy as powder from the chemist. Work better than Oxalic acid.

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[mikeb]

Glad I'm not the only one to make that sort of mistake - I managed to clean the deck after by using that jelly that has an oxalic acid base Y2 or something like that name

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[Deep_6]

Have you sanded down your woodwork with wire wool prior to a lick of varnish? I aways use the nylon scouring pads after the same thing with my decks one season.

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