Hull waterline stain removal

[Denek]

Hi all.
can anyone recommend something to remove the stains from the waterline on my scanmar 33. This was an issue last year too and I ended up having to leave some of it as I just could not remove it. Polished most out with a t cut type product for boat hulls but would rather not do that continuously.
I read somewhere ( possibly on here) that brick acid works but I tried this today and it was hopeless. Any suggestions gratefully received.

 

[XDC]

Y10

 

[VicS]

Hi all.
can anyone recommend something to remove the stains from the waterline on my scanmar 33. This was an issue last year too and I ended up having to leave some of it as I just could not remove it. Polished most out with a t cut type product for boat hulls but would rather not do that continuously.
I read somewhere ( possibly on here) that brick acid works but I tried this today and it was hopeless. Any suggestions gratefully received.

As said Y10 but it is oxalic acid based which does not work at low ambient temperatures

The alternative to Y10 is an oxalic acid solution thickened with wallpaper paste

BUT read the safety data for oxalic acid

 

[johnalison]

One of the oxalic acid versions, or the stuff itself if you want. One problem is that once you start, you may find that you need to do the whole hull to match. I use Yachticon 'Anti-gilb' which is much the same as Y10 but comes in a bigger bottle and is more liquid. Rinse off after use, then wax or polish.

 

[Bran]

Harpic, extra strength, get the ten times extra strength version. Excellent for all waterline buildup. Contains HCl acid, will not damage gel coat or fibreglass. Have used it for years, cheap and effective. Cover the area needed, leave few minutes then rinse off, repeat as necessary, it’s so cheap.

 

[LadyInBed]

I've been using Harpic for 20 odd years, wipe it on, you think nothing is happening but leave for about 15 mins and the brown stain has disappeared, then wash over with clean water.
At a £1 a bottle, what's not to like, and you can use it in your toilet!
Note that it doesn't work on green organic growth or black rubber scuffs.

 

[William_H]

I get that brown stain on my little boat after 2 months in water. If your stain is the same it is easily removed with an acid. A half lemon will move it but mostly I use a stain remover (oxalic acid like) . I fill a squirty bottle and swim around spraying. Yes the snorkel takes my breathing air from away from the spray mostly. Needs it now. ol'will

 

[Denek]

Thanks guys I will try one of these options.

 

[Graham376]

Loads of oxalic on ebay, 500g pack lasts for years but, as others have said, needs warm weather to work properly.

oxalic acid crystals | eBay

 

[pessimist]

I've been using Harpic for 20 odd years, wipe it on, you think nothing is happening but leave for about 15 mins and the brown stain has disappeared, then wash over with clean water.
At a £1 a bottle, what's not to like, and you can use it in your toilet!
Note that it doesn't work on green organic growth or black rubber scuffs.

Any idea what might work on green organic growth above the waterline? We have a considerable quantity between the hulls. Pressure washing didn't touch it and it's now dried on.

 

[Moodysailor]

A tip we got from someone else recently that worked a treat was the "magic erasers". Bought a large pack for dirt cheap of Amazon, they work a treat. I'm not a fan or harsh acids on GRP. We had the boat out of the water so at the same time compounded back and re-waxed the hull to make it a bit less sticky next season.

 

[XDC]

Green growth: A small sponge with an abrasive side, Jif/Cif type of kitchen cleaner, water and lots of rubbing ?

 

[pessimist]

Green growth: A small sponge with an abrasive side, Jif/Cif type of kitchen cleaner, water and lots of rubbing ?

Thanks, I'll give it a try.

 

[harvey38]

Just had a compound cut and wax....

 

[Graham376]

A tip we got from someone else recently that worked a treat was the "magic erasers". Bought a large pack for dirt cheap of Amazon, they work a treat. I'm not a fan or harsh acids on GRP. We had the boat out of the water so at the same time compounded back and re-waxed the hull to make it a bit less sticky next season.

Magic sponges are abrasive melamine and work by sanding so don't use in the same area too often.

 

[Graham376]

Green growth: A small sponge with an abrasive side, Jif/Cif type of kitchen cleaner, water and lots of rubbing ?

Or Scotchbrite pads. I found some coarse ones with a plastic backing and handle.

 

[RJJ]

Loads of oxalic on ebay, 500g pack lasts for years but, as others have said, needs warm weather to work properly.

oxalic acid crystals | eBay

Any views on the best way/ratio to make it sticky? I tried wallpaper paste last year and it went lumpy straight away. Thanks!

 

[Graham376]

Any views on the best way/ratio to make it sticky? I tried wallpaper paste last year and it went lumpy straight away. Thanks!

We have much higher winter temperatures than UK so just brush on as liquid and it works quickly enough without being a paste. Maybe if you make up wallpaper paste first with warm water then add dilute oxalic, it may not go lumpy? Oxalic by the way dissolves best in hot water.

 

[LadyInBed]

Green growth: A small sponge with an abrasive side, Jif/Cif type of kitchen cleaner, water and lots of rubbing ?

? That's how I do it.

 

[VicS]

Any views on the best way/ratio to make it sticky? I tried wallpaper paste last year and it went lumpy straight away. Thanks!

I found this recipe on the Ribnet forum for rust stain removal

1 litre of luke warm water
200g Oxalic acid powder (ebay)
50mls car wash detergent (any mild liquid detergent)
Wallpaper paste powder (to required consistency)

Add the acid to the water. Slowly add paste powder until mix starts to gel. Go short and leave it a while - it thickens for a few minutes. Then add detergent. Brush on, leave 10-15 mins and pressure wash off. Avoid galvanised metals, chrome etc. Wear PPE. Safe on stainless steel.

But oxalic acid is not as soluble as this suggests. Some will crystallise out as it cools I am sure Therefore reduce it to between 100g and 150 g / litre