Stained Water line on GRP Hull

[Geoff Wode]

Wear ppe when using oxallic acid. Consumer products contain “safe” proportions in solution.
It’s pretty toxic stuff in crystal form. Kidney failure with sufficient exposure.
Definitely don’t dry sand wood treated with OA.

 

[William_H]

I use oxalic ac id to clean the brown stain. However I have found also that a hlf lemon pressed onto the surface will shift the stain. Acid of any sort them is the answer. Oven cleaner as I understand is mainly caustic soda which is very goopd at cutting oil;s and grease. ol'will

 

[Refueler]

Increasingly hard to find
Internet price £12.00 for 500g . Use cheapo washing up liquid to get to adhere to vertical surfaces and chines etc £15.00 all in ?

"Y"10 at £16-"£20 per face cream sized container is only about 28g of Oxalic acid per pot, suspect the water base makes up most of the rest of the weight.

Over here Oxalic is sold as Concrete / Builders cleaner and is 6 euros a kilo.