Oxalic acid concentration for hull cleaning
- Thread starter Simon 420
- Start date
VicS
Well-Known Member
Somebody been using a grinder nearby to grind or cut steel ......... The little hot particles can imbed themselves into the surface of grp and then rust, You clean away the rust stains but the particles remain and the rust stains reappear.
MM5AHO
Well-Known Member
I add powdered oxalic to warm water until no more will dissolve. Then I add about 5% by volume dishwash liquid. I then use this mix to scrub the deck with a brush until it foams. The foam slows down evaporation and also does some cleaning. Rinse in water.
alancollins
Well-Known Member
Other younger boats next to mine in the boatyard are not affected. I hadn't thought of using a detergent with the acid solution. Could it be that simply flushing the decks is not enough?
KREW2
Well-Known Member
On a horizontal surface only an acid solution should do it. The soap just lets it adhere a little longer to a vertical surface.
Poignard
Well-Known Member
In hot weather, be careful not to add too much wallpaperpaste to thicken the oxalic acid solution. If you're not quick enough washing it off you can find yourself with extra work scraping off the residue.
How do I know this?
How do I know this?
Humblebee
Well-Known Member
Good tip, thanks for that Refueler.
Refueler
Well-Known Member
The main point of using Oxalic - is you REDUCE the amount of work needed to remove stains / clean surface.
Personally I prefer Oxalic removing the stains than my rubbing with a Cutting agent ....
oldgit
Well-Known Member
Any "cutting back" agent will use some sort of grinding agent reducing the thickness and scoring the surface of the Gel coat, probably over time allowing staining to penetrate the gel coat even further.
Difficult to avoid any boot lines, painted or vinyl and have frequently managed a blue or red smear over adjacent white hull when using a abrasive paste.
Do use "Silky" a very mild cleaner . Budget priced paste which does not have the words Marine or Star ***** anywhere on the container.
Refueler
Well-Known Member
For mild staining ... any of the Toilet Bowl Cleaners will usually shift them ...... Cilit Bank Lime and Rust was really good until formulation was changed.
Even T-Cut ... Bluebell .... Silverin ..... will cut a tiny amount of surface away ..... not a good idea with Gelcoat. But I think we've all done it.
Even T-Cut ... Bluebell .... Silverin ..... will cut a tiny amount of surface away ..... not a good idea with Gelcoat. But I think we've all done it.
Poignard
Well-Known Member
What's the best way of dealing with this black staining around the exhaust skin fitting?
I think it occurs when the boat pitches, submerging the skin fitting and washing muck out of the exhaust pipe.
Oxalic acid won't shift it. I usually get it off with elbow grease and CIF, but CIF is mildly abrasive and I am not entirely happy using it.
I think it occurs when the boat pitches, submerging the skin fitting and washing muck out of the exhaust pipe.
Oxalic acid won't shift it. I usually get it off with elbow grease and CIF, but CIF is mildly abrasive and I am not entirely happy using it.
Refueler
Well-Known Member
My Transom is often black for large area due to the soot thrown out if I over-rev .... I use Toilet Cleaner ..... Harpic or similar.
Its interesting that even at our 'slow speeds' .... I can see the exhaust 'smoke' curling back towards the transom same as the crap that gets into that area behind your car dirtying up the rear window....
Its interesting that even at our 'slow speeds' .... I can see the exhaust 'smoke' curling back towards the transom same as the crap that gets into that area behind your car dirtying up the rear window....
Mistroma
Well-Known Member
I was always surprised to find people trying to clean a dirty boat with oxalic and I'd point them towards Cif or just plain detergent for light dirt.
My old Southerly 95 was prone to soot build up around the exhaust on a flat stern. Cif usually did a decent job if used regularly during the season when the soot build up wasn't too bad. I was lucky enough to have quite a large exhaust, able to take a section of plastic pipe. I sanded it slightly to allow it to slide in about 1" and cut the outer end at 45 degrees. It worked well on a flat upright stern with the point near the water, pushing water away whenever it became submerged. Soot build-up was hugely reduced and I only needed to clean it one each season. Might not work as well with your transom as it might just end up with soot higher up above the waterline.
My old Southerly 95 was prone to soot build up around the exhaust on a flat stern. Cif usually did a decent job if used regularly during the season when the soot build up wasn't too bad. I was lucky enough to have quite a large exhaust, able to take a section of plastic pipe. I sanded it slightly to allow it to slide in about 1" and cut the outer end at 45 degrees. It worked well on a flat upright stern with the point near the water, pushing water away whenever it became submerged. Soot build-up was hugely reduced and I only needed to clean it one each season. Might not work as well with your transom as it might just end up with soot higher up above the waterline.
Poignard
Well-Known Member
Might be worth a try if I can find a suitable bit of tube.
Refueler
Well-Known Member
I did just that ..... added an extension tube to try and reduce the soot staining .... TBH - did not make much difference ... over time tube has got shorter !! No different !
Here's immediately engine started .... you can make out the extra tube .... (rubbing strake is ordered for replacement in spring)
Here's after an Oxalic clean ... ready to be 'polished' .... you can see the pipe ...
Mistroma
Well-Known Member
I had a piece of spare white pipe from a sink drain and it was a tight fit. I was planning to cut a slot if it was oversize but was so close that I only needed some light sanding. I think it was in place for many years. I sold that boat in 2009 and my wife's memory is that it stopped most of the heavy soot around the exhaust. However, her memory is that the entire stern still got a light covering and became grey. I'd forgotten that but do now remember cleaning it with detergent a couple of times during the season. It came off easily and wasn't ingrained an longer. Worth a try as it's cheap and easy to do but I imagine shape of stern and exhaust location will have a big effect. Mine was close to the waterline, well away from the centre and exposed to any wind.
Refueler
Well-Known Member
My pipe is that plastic white pipe that has a wire spiral in it ... so its ribbed. It literally screwed into the existing exhaust pipe hull fitting.
It doesn't have to be heat resistant as you have cooling water through it as well.
It doesn't have to be heat resistant as you have cooling water through it as well.