Very bad rust on gelcoat through grinding, best removal.

[JOHNPEET]

I had a very similar experience last winter. I chose to do the clean myself as I didn’t want to take the chance that the damage may have been made worse!
I had great success with Y10. Paint the gel on, leave for a good ten mins, agitate with a paint brush, leave for another ten mins then rinse off. Only problem I had was the Y10 was occasionally drying in the breeze and became ineffective, so kept having to reapply. Also needs to be used above 10 degrees I think. I used it on all surfaces, 2 pack paint, alloy window frames, glass, stainless and acrylic sheet (hatch windows)
It’s not a quick job! Obviously depends on the extent of the contamination, but it took me about four days in total - 12m fly bridge motor boat.

 

[oldgit]

Many many years ago somebody was doing a serious bit of grinding on steel tug moored next to my Princess 33.
All the flat surfaces aquired an interesting speckly pantina after the first rain fell.
Applied a coat of Oxylic Acid and left to dry.
It took several weeks before the rusty specs became virtually impossible to see and all vanished eventually with second coat.

My brother was responsible for coating a posh Gin Palace with a really heavy coating of grinder dust.
He contacted a local valeting and polishing company and they sorted it within mornings work.

Suspect a common problem .
DIY or get somebody else to sort it.
Fast or slow your choice.

 

[wonkywinch]

See my recommendation here, it did a great job removing rust from gelcoat after I'd sawed through an anchor chain ..

Cleaning / repainting oily lockers and bilge

 

[PetiteFleur]

I've used Y10 successfully when I managed to get some rust stains when I did some angle grinding...

 

[ducked]

Maybe supplement above treatments with a few intervening passes with a really strong magnet?