Oxalic acid not removing all waterline stains. recommendations please

capetown

capetown

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Y10 has removed most but there are a couple of areas where it's only partially worked.
Don't want to use any abrasives/cutting compounds.
That's the background.
So, what's worked for you guys?
Cheers
 
Just a thought, I don't know what the UK temperature is just now but oxalic acid is very temperature sensitive. The rate of reaction drops off very quickly and is very very slow below 10C. Increasing the temperature will make it work a lot faster. You can dissolve it in fairly warm water and preheat the stained areas with hot water before applying the oxalic.

You can watch most stains vanish as you watch if temp above 25C or leave it to soak for a week at 10C (slight exaggeration)). Might be worth trying and if stains still won't budge it's time for something a bit more aggressive (i.e. abrasive).
 
I used to use EasyClean which had been recommended in the mags. Mrs Poecheng laughed when I said how easy it was to get rid of stains - just spray it on and they disappear before your eyes. She laughed as it looked like water. Then she saw it work !
It was great and got rid of everything (including the non-reflective layer on my spectacles !)

Looks like it has disappeared now as the website goes to a webhosting thingy. Shame
 
I use a mixture of oxalic and phosphoric which has been effective on black stains which oxalic doesn't remove sometimes.

http://www.wickes.co.uk/Wickes-Grout-Film-Remover-1L/p/166088

"A concentrated, biodegradable cleaner for removing cement film and grout bloom residues from glazed floor tiles, quarry tiles, unglazed floor tiles and natural slate. Will not damage the grout or tiles|
• Approx coverage between 20-50m2 per litre depending on dilution used.
• Removes cement grout film after installation without damaging grout
• Suitable for use on glazed ceramic, quarry, slate, granite and terracotta tiles
• Can be used to neutralise efflorescence, white salt stains from brick, flags or terracotta tiles and remove rust and oxide stains from other surfaces such as chrome and stainless steel
• Not to be used on marble or other acid-sensitive materials
• Does not give off fumes"

I use it neat on a sponge or cloth it is a very dilute solution. see the coshh data sheet in the link.

cheaper than any marine equivalent!
 
I usually use Oxalic acid, as strong as I can make it. Keep adding the powder until no more will dissolve in a small amount of warm water. That has always removed any stains I have had on the water line. I usually leave it for about 20mins before washing it off especially if the temperature is a bit lower than ideal. I did use Brick cleaner last year to remove the East Coast mud scale/staining that we get on drying mud moorings. Whilst doing that I wiped it over the water line stain and it took that off as well. However I did end up with a definite mark on the hull about a foot or so up where I had ended the Brick cleaner that I couldn't then seem to get rid of. I haven't noticed it recently so hopefully it has faded back in. I guess if you have some form of oil staining, some form of solvent as already suggested or White spirit may shift it.

I have just noticed you said you have used Y10, which probably isn't as strong as mixing your own Oxalic solution. Oxalic acid powder or crystals is quite cheap to buy on ebay and it will last for ages.
 
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All the above are good suggestions and would normally work very well.

That said there's more that can be done to make life a little easier.

When stains are 'holding' it is usually down to the surface itself.

Imagine looking at the surface close up under magnification and likening it to your fingers spread apart. The stains that are refusing to shift are closer to the palm of your hand.
Normal cleaning would be effective but only down as far as the finger nail level. If you do manage to clean out the full depth of the stains with an effective cleaner, a vacancy opens up.

This cycle can be broken, but it would involve correction techniques.

As you don't want to go down the correction route (can I ask why?) I would suggest that you determine what it is that has actually caused the staining, if it is something that Y10 (whiten) wouldn't touch.

Think of getting two stains out of a shirt, one weetabix the other lipstick, both would require a different technique. It's no different on a hull, some cleaners only work on certain contaminates and are useless on others.

Just a note: Plenty of fake / cheap Oxalic out there, some will work well and others not so much.

Also it might be worth pointing out that I don't carry any Oxalic acid on board and haven't used any for ages. Read into that what you may.

I would normally clean a hull with 2 or more different types of cleaner depending on what I thought was on there and conditions / work plans etc.

Rather than force one cleaner to struggle with the things it can't get, just concentrate on the things it can and switch over to the other for the second pass - much faster despite two washes.

Taking oxalic as an example, if a hull had severe water spots all over, then a simple wash with shampoo won't work at all, there is almost no point in trying, where the oxalic will cut through and dissolve the TDS in seconds, as will vinegar etc.
Now considering you would need to wash off the oxalic residue anyway with the shampoo, it makes sense to start with the oxalic and follow with shampoo.


Personally I would want it corrected and pop a 'no vacancies' sign up. But that would involve correction.
 
nigelmercier said:
My best results have been with an Oxalic based cleaner with added Oxalic crystals to saturation. Most cleaners have surfactants which allow the acid to soak into the stains better.
Click to expand...

I mostly stick with oxalic and add a dash of something like Fairy liquid (being a natural cheapskate). I'd expect that to have a mix on anionic and non-ionic surfactants as it would be expected to function over a range of water types (hardness). Sound principle and remember temp. as well if it's UK weather. Reaction is very slow below 10C and I try to get around 20C+ (pre-heat surface with hot water and use warm solution, or move to Spain :D).
 
Hi Guys, been in Hospital, back on the mend now.
Thanks for all the replies.
Okay, i've tried, neat household bleach, Hydrocric acid @ 36%, white vinegar but as Marine Refletions noted it seems to be the surface, 2000 w/d removes it.
I removed all the waterline tapes as they were tatty with the intention of replacing them, I didn't realise how difficicult it is so gave up, so I'm going to raise the waterline instead.
Didn't want to abraide at the time as the untaped gel coat was eroded so much that you could see and feel the ridges. Just thought it might be too thin.
 
I have tried oxalic acid no joy, probably to cold to do it. Tried bleach farcela on a buffer, rubbing compound hardly touched it.
Down the yard today a kind gent told me to use spirit of salts, nipped home came back with some.
Spirit of salts neat on a green scourer came off so easy.
Then washed the salts off did a cracking job.
 
What Mistroma says is right. Buy oxalic crystals at a fraction of the price of Y10 and dissolve in hot water then apply promptly.
 
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