Rust specks on GRP

[barson]

Had to drill out some corroded bolts on a GRP deck and can't have cleaned up all the filings bits - because now I have a rash of tiny rusty specks in the textured GRP slip-free surface. Tried scrubbing with a brush and cleaner etc but they seem to be imbedded. Tried paste clener (Gumption). Any ideas for removal? Would scubbing with a stainless-wire or bronze-wire brush help?

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[Evadne]

Pressure washer or even a brass wire brush and hose pipe for the actual bits of metal, but are you sure its not just staining? Rust seems to seep into gelcoat and paint after a short period of contact. Oxalic acid (aka rust stain inhibitor) gets rid of the stains themselves very well.

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[kds]

Y10 paste is the expensive answer - or any of the acids. Don't use a wire brush on GRP gelcoat.
Ken

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[barson]

You're probably right - I suspect the metal bits are no longer there and its a rust stain from where they were. I'll try the oxalid acid - certainyl helped whiten up the deck when used previously. Still cursing for not cleaning up more better.

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[Evadne]

It's worth a try. On reflection Ken is probably right about not wire-brushing gelcoat, unless you're planning on painting it afterwards!

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[kireonriley]

just to remove stain use harpic limescale toilet cleaner cost about one pound just aply neat and wach the stain disapear and then rinse of ,it will also clean those awfull brown stains on youre hull KIERON

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[AndrewB]

Oxalic or even better dilute phosphoric acid. I believe that Starbrite boat cleaner as sold by all chandlers is a mix. Teak cleaner which is oxalic acid also works but is less effective. Expect to have to repeat this treatment a few times.

The filings were hot and will have embedded themselves slightly in the GRP. They cannot be easily removed by abrasion (wire-brushing, vim or similar), which in any case will do nothing for your finish. The stain, which is out of all proportion to the size of the filings, is impervious to bleach.

 

[VicS]

The trouble you may have, especially if you used a power drill, is that hot particles have melted their way into the surface of tha gel coat. If this has happened you will probably have to clean up the stains as they reappear until it has all gone. I have cleaner which contains oxalic acid which is very effective. It was probably expensive but in 25+ years I've still not used it up so its not expensive in the long run.

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[charles_reed]

Use an artists\'

paintbrush and saturated oxalic acid solution.

Mechanical abrasion will get rid of the marks and the gel-coat.

Put some solution on each of the marks and leave it there for about 15mins, then wash it off with lots of fresh water. repeat this as many times as are needed.

the marks will gradually disappear.

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[Rohorn]

Re: Use an artists\'

Hi...in other posts rhubarb has been cited as a source of oxalic acid...remember the inside of the saucepan after cooking the stuff up? I've never heard of the Harpic solution before..... I do have some unsightly grey-brown stains leaching out through the gel-coat on my cat....might try Harpic on that!. Cheers....R

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[pappaecho]

The best remover of all things iron is citric acid from the chemist, or your local firendly home brew shop. Citric is used in food, drugs food etc and is harmless - oxalic acid is not!
Citirc acid chelates the iron molecules so you can wash them off. Citric acid is also very effective at dissolving stainless steel, so wash off thoroughly to avoid staining.
Lastly a few drops in a G&T gives it added zing

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[doca]

I have'nt carried out any metal drilling on my deck but there are what looks like rust specks on it. I will try and remove them as part of the various winter tasks to be done but I am not sure what causes them. Maybe some airborne metal from somewhere in the harbour.

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[VicS]

Are you any where near an engineering works where they may be grinding or welding? Another source of tiny metal particles and rust marks is the sparks from train brakes so you get the problem if you are near a railway especially if the trains are braking as they approach a station. Its true!

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[doca]

No trains. The only commercial activity in the immediate area is grain loading from ships. Maybe the ships maintenance operations let off some sparks from time to time.

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[Evadne]

The grit used by our boatyard in their gritblaster is at least partly ferrous. I know because it landed on and stuck to some freshly painted toplac on the deck. /forums/images/icons/mad.gif

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