Cleaning and painting the engine bilge

[Jak]

16 hours ago, rusty69 said:

Yes put a tub beneath the leaking gland with a bilge pump in, or a separate pump/pipe.

 

If Its Rainwater, find the leak and fix it. 

Thanks for this. I've mopped dry and tightened up the greaser. I know the rainwater gets on from the drainage channel under the access plate to the weed hatch.  Design is cr*p and drain always getting blocked...

[WotEver]

17 hours ago, Froggy said:

why hack away at rust scale that isn't easily removable rather than neutralise the rust then paint over it?

Because thick layers of rust won't all get neutralised because the treatment can't get at it. 

[Froggy]

On 07/08/2017 at 15:53, WotEver said:

Because thick layers of rust won't all get neutralised because the treatment can't get at it. 

So are you saying that it will continue to rust even though oxygen and water no longer reach it? Even the instructions for Vatcan say to scrape away loose rust with a wire brush and don't mention hacking away at anything beyond that.

[dmr]

13 minutes ago, Froggy said:

So are you saying that it will continue to rust even though oxygen and water no longer reach it? Even the instructions for Vatcan say to scrape away loose rust with a wire brush and don't mention hacking away at anything beyond that.

Rust is strange and destructive stuff. I don't fully understand the mechanism but from much experience have observed that it appears to hold its own supply of water and oxygen and so the rusting process can continue for some time after it has been sealed by painting over it. If you do a 99% job of removing the rust then it should be ok and the rust will stop. If you leave too much rust behind then new rusting  continues and this perforates the paint surface and lets new water and air in and all your effort was in vain. A related phenomenon is the way that rust progresses under seemingly intact paintwork, bringing in its air and water from a perforation some distance away. When you rub down a tiny paint blister you often find the rust below it to be quite extensive. It ain't called tinworm for nothing, it digs itself a burrow.

................Dave

[BEngo]

12 minutes ago, Froggy said:

So are you saying that it will continue to rust even though oxygen and water no longer reach it? Even the instructions for Vatcan say to scrape away loose rust with a wire brush and don't mention hacking away at anything beyond that.

Rust continues happily to grow under the best coatings in the world. There is enough moisture trapped by the coating to keep the chemistry going. Get off as much rust as you can woth scrapers and other mechanical means then treat what is left.  Ensure you use enough to soak the rust in yhe bottom of any pits then prime and paint. 

N

[Froggy]

18 minutes ago, dmr said:

Rust is strange and destructive stuff. I don't fully understand the mechanism but from much experience have observed that it appears to hold its own supply of water and oxygen and so the rusting process can continue for some time after it has been sealed by painting over it. If you do a 99% job of removing the rust then it should be ok and the rust will stop. If you leave too much rust behind then new rusting  continues and this perforates the paint surface and lets new water and air in and all your effort was in vain. A related phenomenon is the way that rust progresses under seemingly intact paintwork, bringing in its air and water from a perforation some distance away. When you rub down a tiny paint blister you often find the rust below it to be quite extensive. It ain't called tinworm for nothing, it digs itself a burrow.

................Dave

 

15 minutes ago, BEngo said:

Rust continues happily to grow under the best coatings in the world. There is enough moisture trapped by the coating to keep the chemistry going. Get off as much rust as you can woth scrapers and other mechanical means then treat what is left.  Ensure you use enough to soak the rust in yhe bottom of any pits then prime and paint. 

N

Many thanks for this advice.

[Grassman]

On 05/08/2017 at 16:37, WotEver said:

Because of the requirement to wash off Fertan and the fact that 1) this introduces water into exactly the place you don't want it and 2) if you don't do a thorough job of washing it off the paint won't stick... I much prefer Vactan. 

Tony

I always use Vactan used it last year in my engine bilge when the engine had been removed. I painted over it when it was dry and so far it appears to have done the job. Last month after having burnt off all the old blacking I applied it to my hull before re-blacking with 3 coats. I'll let you know in a couple of years time whether it's worked or not .

I knew you could apply paint on top of it wasn't sure about bitumen, so before I did it I checked with the very helpful chap at Vactan and he said it should also be fine applying bitumen based blacking on top of it.