Oxalic acid on a blue hull?

[westhinder]

The blue hull of my new (to me) boat has two bands of white gelcoat parallel to the waterline. The white bands show brown stains.
On my previous white boat I used oxalic acid to remove that kind of stains. If I use it on the white bands, do I risk discolouring the blue surface next to them if the oxalic acid touches it?

 

[pvb]

No, but if you don't believe me try a small test patch first in an out-of-the-way place.

 

[VicS]

+1

 

[westhinder]

Thanks guys

 

[SAMYL]

Sainsbury's Ceramic Hob Cleaner works quite well.

 

[gjgm]

The blue hull of my new (to me) boat has two bands of white gelcoat parallel to the waterline. The white bands show brown stains.
On my previous white boat I used oxalic acid to remove that kind of stains. If I use it on the white bands, do I risk discolouring the blue surface next to them if the oxalic acid touches it?

No, but I think you might find the blue also "cleans". When I clean the white deck with acid, it leaves streak marks through the blue hull. They do clean out, but they are pretty onbvious at first.
I think I would be careful along the blue/white line and save alot of grief

 

[ProDave]

Aldi Caravan Cleaner, £2.99 for 1 litre, cleand my hull a treat.

 

[BlueChip]

No, but I think you might find the blue also "cleans". When I clean the white deck with acid, it leaves streak marks through the blue hull. They do clean out, but they are pretty onbvious at first.
I think I would be careful along the blue/white line and save alot of grief

+1

 

[Marine Reflections]

The blue hull of my new (to me) boat has two bands of white gelcoat parallel to the waterline. The white bands show brown stains.
On my previous white boat I used oxalic acid to remove that kind of stains. If I use it on the white bands, do I risk discolouring the blue surface next to them if the oxalic acid touches it?

No, no danger there, but as pvb says a little test patch, always a good idea if not just for learning.

If the blue is very oxidised and chalky, then you will also be removing some of the 'dead' gel, blue & white, it will change the colour, but only to a more blue if anything, just as the white returns more.

The problem lies in not properly rinsing off the solution on occasion.

Common to find blue hulls that have had the teak decks cleaned with an oxalic solution but have allowed the solution to run down the hull, this will cause a problem over time as it will be almost an invisible assassin.

You can tell the difference as there will be 'runs' in the oxidation where it has prematurely aged.

Think it's all rinsed off and the strength of the solution has been neutralised?

If not and this dries it will accelerate the ageing / oxidation process.

Simply because it has removed any protection and continues to attack the surface.

It happens just the same on white hulls of course but it is not noticed as easily as blue and is not restricted to just oxalic, all cleaners need to be completely rinsed off until neutral.

When it's out or when you can, make sure you have a suitable wax / sealant layer on a decent finish to prevent staining in future.