Rust stain on GRP

[brians]

I have some serious rust staining on white GRP hull. Fortunately it is not a big area but is unsightly none the less. What is the best product to use? As it is a serious (deep) stain my usual cleaners have minimal if any effect.

 

[fisherman]

Oxalic acid. There is a particular seaweed, green, long thin flat leaves, that will do the job, alginic acid I think.

 

[TQA]

OXALIC ACID !

Find something with that in it and it will do the trick. You can buy it in powder form and make your own.

At the chandlers ON OFF works as does Starbrite rust remover.

 

[richardbrennan]

Y-10 is the stuff that they sell in chandlers, it's basically an oxalic acid gel, which is useful on vertical surfaces as it stays put. It's obviously more expensive than making it up yourself, but as you say the area is small, I'm assuming this will not be a major factor. I think it's about £10 for a pot.

 

[VicS]

If you have any in the kitchen cupboard well worth trying Cillit Bang Grime and Lime. Rust stains are one of the stains they claim it will remove.

If it does not work then you probably wont beat Y10, oxalic acid or another oxalic acid based cleaner.
If you opt for oxalic acid thicken a near saturated solution with wallpaper paste for use on vertical surfaces.

Remember oxalic acid is toxic and is also harmful buy skin absorption. The odd person has also suffered a very severe reaction to splashes on the skin too.

Gloves and goggles essential kit. Wash splashes off immediately. Dispose of residues responsibly. Label anything you keep clearly too

 

[richardh10]

Following advice on here I used oxalis acid, and it certainly did the trick. I bought a tub on eBay for next to nothing

 

[nigelmercier]

Another vote for Oxalic Acid. I normally dilute at about 10:1, say 100g in a litre of water.

You can thicken with a little wallpaper adhesive, I plan to try xanthan gum next time.

 

[AngusMcDoon]

After the oxalic acid treatment, wap on some polish for GRP to stop it getting a pale brown stain over the next season.

 

[C08]

Having had a number of old boats with rusting rubbing rail bolts and bad stains on the hull and also some "stainless staining" I have tried all sorts of stuff including oxalic acid. The best I have found (but not the cheapest) is Starbrite Rust Stain Remover in a spray bottle. I do not know what is in it but I have done sample areas with Oxalic Acid for comparison and the Starbrite Spray and the Starbrite is quicker and more effective in my experience.

 

[rbmatthews]

+1 for oxalic acid with a dash of wallpaper paste to make it stick to vertical surfaces. I bought 1kg thru ebay for £6, postage free. Mixed at around 140 g per litre, 1 litre was more than enough for our 5.5 m LOA up to the rubbing strake. Painted on with a wallpaper brush. It took about 3 minutes to work, but I left it on for about 15 minutes, then hosed it all off with a high pressure hose. The difference was unbelievable. Gloves and goggles recommended as it is difficult not to splash a bit as you put it on. Marvellous stuff.

Rob.

 

[nigelmercier]

... Starbrite is quicker and more effective in my experience.

It has a surfactant in it, so if the surface is greasy, add a bit of pH neutral liquid soap.