Sand and paint

[Amphibian Man]

Hello everyone,

When I got my boat a few months ago the roof was covered in years of bird poo and moss and mould. It was caked on. I have eventually cleaned it off but what's left looks terrible. Sand and paint mix I think plus patches of rust. I can't chip away at the sand and paint. It is solid. Can someone tell me what to do please. Do I get rid of the visible rust and just sand and paint over it all, including existing sand and paint? Or do I have to get the whole roof down to bare steel again? And if so, how? I feel clueless. Any advice would be very welcome.

Cheers.

[cuthound]

I've seen professional boat painters use a needle gun to remove the sanded paint. Alternatively a scabbler can be used.

 

However unless you remove all of the sanded area and repaint, any repairs will be obvious.

Edited April 25, 2023 by cuthound

[Tracy D'arth]

 A Rotary Scabbler will take it all off but take the bulbs out of your roof lights first!  Hire from the tool hire shops.

They look like this    https://www.travisperkins.co.uk/cleaning-and-floor-preparation-hire/concrete-scabbler-hand-held-110v/p/142138    or you can just buy the tungsten carbide wheels on a 4" angle grinder disk.  Wear lots of protection for eyes and face and body.

You will have to chip out the corners by hand with a chisel.

 

It all has to go or you will just be painting every year over the mess.

 

Good rustproofing like Vactan then prime and undercoat and top coat as soon as you can. Primer is porous, the rust wil break through if you don't get top coat on fast.

[David Mack]

I used flap discs in an angle grinder to take multiple coats of paint and rust off my cabin roof back to bare metal. The flap disc leaves a slightly rough texture surface to the steel which is good for a paint bond, but don't let the disc linger longer than necessary in one spot as it will continue to grind away the steel. The process is however very slow.

Awkward corners where the flap disc wouldn't fit were cleaned off with a cup wire brush in the angle grinder. This gets loose paint and rust off, but not that which is firmly attached, and it tends to polish the steel surface.

https://www.toolstation.com/flap-disc/p60521

[BEngo]

Remove it all, to bare metal.  Use a scabbler, with carbide wheels, not HSS, a needle gun or a Tercoo rotating blaster in an angel grinder.  Good PPE essential. An old chisel and elbow grease, or an electric chisel,  are good for corners.

 

If it is rusty, remove all the roof furniture, like mushrooms and vents, of the rust will come back from beneath them.  Treat rust.    Prime, paint.  Try not to get overnight condensation on the primer or undercoat.  If you want a low slip surface then try the top coat with rubbery granules.  A lot easier to get off than sand.

N

[IanD]

17 minutes ago, BEngo said:

Remove it all, to bare metal.  Use a scabbler, with carbide wheels, not HSS, a needle gun or a Tercoo rotating blaster in an angel grinder.  Good PPE essential. An old chisel and elbow grease, or an electric chisel,  are good for corners.

 

If it is rusty, remove all the roof furniture, like mushrooms and vents, of the rust will come back from beneath them.  Treat rust.    Prime, paint.  Try not to get overnight condensation on the primer or undercoat.  If you want a low slip surface then try the top coat with rubbery granules.  A lot easier to get off than sand.

N

I'm not sure this lot would be very helpful as far as removing paint is concerned -- unless their sound is *really* terrible... 😉

 

https://www.facebook.com/AngelGrinderMA/

[Tracy D'arth]

1 minute ago, IanD said:

I'm not sure this lot would be very helpful as far as removing paint is concerned -- unless their sound is *really* terrible... 😉

 

https://www.facebook.com/AngelGrinderMA/

Thankfully I am one of the brighter ones on here who does not do Face book rubbish so can't see what it was.

[IanD]

10 minutes ago, Tracy D'arth said:

Thankfully I am one of the brighter ones on here who does not do Face book rubbish so can't see what it was.

You can read their name though, can't you? 😉

[Tracy D'arth]

8 minutes ago, IanD said:

You can read their name though, can't you? 😉

No, I don't have an account.  Never heard of it, is it a spelling mistake?

[IanD]

1 minute ago, Tracy D'arth said:

No, I don't have an account.  Never heard of it, is it a spelling mistake?

<sigh> no, that was the joke -- of course you don't  need any FB account to read the name of the link in the post... 😉

[Higgs]

As others have said, use a scabbler. No messing about. Efficient. Doesn't create lots of dust, but larger pieces. I also use several good quality rigid scrapers, kept with an edge. These will get right under the paint, in tight areas the scabbler can't reach. A scabbler will clear a roof in a couple of hours. The teeth should be good enough for concrete. After you've cleared the roof, you can begin to clean the surface with sanders, etc. 

 

I wouldn't bother with a needle gun, they're too bloody noisy.

 

 

Edited April 25, 2023 by Higgs

[Amphibian Man]

Hi all,

Thanks for all the advice. Does Vaclan take the place of red oxide or primer? Can you paint over vaclan without the need for red oxide or primer?

[LadyG]

1 hour ago, Amphibian Man said:

Hi all,

Thanks for all the advice. Does Vaclan take the place of red oxide or primer? Can you paint over vaclan without the need for red oxide or primer?

With all these things the best thing is to read the data sheet, and if it is same as forum opinion you've nailed it.

[Tony Brooks]

2 hours ago, Amphibian Man said:

Hi all,

Thanks for all the advice. Does Vaclan take the place of red oxide or primer? Can you paint over vaclan without the need for red oxide or primer?

 

As Vactan leaves a coating on the surface, any primer then is supposed to react with the steel is unlikely to react, but according to Vactan an ordinary primer should stick.