At the Twister meeting in February I scribbled a few notes during the afternoon discussion session.
One reads "Vitamin C powder to remove brown stains from hull" .
Can this be true or did I have too much beer with my lunch?
If it is true, is it better than oxalic acid and how do you apply it?
And where can you buy it?
You can buy it in bulk from the web. I found this link: https://www.tradeingredients.com/ascorbic-acid-powder
Having looked it up I note that in the presence of oxygen it will decompose; one of the decomposition products is oxalic acid.
You'd apply it as a concentrated solution in warm water. Probably be good to add a splash of washing up liquid. If you have waxed the hull you'd need to wash that off first.
Trouble is that most suppliers will supply a pharmaceutical grade. This adds cost to the basic product.
I'm pretty sure it will work. I know it will remove rust stains - but so will phosphoric acid. That's cheap on the web.
I use Star Brite Hull Cleaner. It's very very good at removing the yellow brown stain that appears. Tip: it will discolour any antifouling - so if the boat is out of the water clean topsides first. Just wipe it on. Wait, then rinse off. Use gloves. It's acid. It's expensive but one bottle last several years.
I've looked up the composition of the Star Brite product by looking at the Material Safety Data Sheet. It's basically a 5 to 10% solution of oxalic acid with a surfacant. [i.e. a detergent. This is to 'wet out' the solution] plus a few other secret safe compounds present in very low quantities that they don't need to declare.
John MacMullen said
So what's wrong with Oxalic acid? A tub of crystals at around £11 generally lasts us for 4 seasons and we clean quite a lot.
Nothing wrong with oxalic acid.
I have used at least once a year during the 23 years I have owned "Tammie Norie"; more frequently since I began keeping her on the River Vilaine, where brown staining is a problem.
But someone mentioned using Vitamin C at the February meeting and I would like to know if there any advantages in doing so.
For example, would it be more effective at low temperatures, and might it be less damaging to the environment than oxalic acid? The authorities in the part of Brittany where "Tammie Norie" is kept are beginning to clamp down hard on activities that they think might cause environmental damage.
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