Bilge paint V Red Oxide

[Manxcat54]

I have been following the Youtube blog Narrowboat precious Jet, and in Winter update #12 he paints the base plate (inside) with red oxide, it looks the business, so have any of you self builds out there used this to any good effect rather than any other paint?

[rusty69]

I was  under the impression that red oxide is porous, so left with no top coat in a wet bilge will not last long. The water based red oxide of today is not a patch on the oil based stuff off old. 

 

I epoxy coated the bilge of our engine room a few years ago, and that has stood up pretty well, but does require good prep. 

[David Schweizer]

1 hour ago, rusty69 said:

I was  under the impression that red oxide is porous, so left with no top coat in a wet bilge will not last long. The water based red oxide of today is not a patch on the oil based stuff off old. 

 

I epoxy coated the bilge of our engine room a few years ago, and that has stood up pretty well, but does require good prep. 

It depends on which Red Oxide paint you choose, I painted my bilges with Finnigans Red Oxde, which is (or used to be) a non porous paint which worked well and showed no rust after more tha ten years. Nowadays I would probably choose Rustoleum Paint.

 

 

Edited February 21 by David Schweizer

[LadyG]

If I needed a good job done the engine would come out and engine hole prepped, then rust removal, then the tough red oxide as long as it will be undercoat to bilge paint. Or use two pack epoxy. Needs to be oil resistant.

Take technical advice from technical adviser of marine paint suppliers, I don't mean the local marina 

[David Mack]

2 hours ago, Manxcat54 said:

I have been following the Youtube blog Narrowboat precious Jet, and in Winter update #12 he paints the base plate (inside) with red oxide, it looks the business, so have any of you self builds out there used this to any good effect rather than any other paint?

Is this red oxide, as in red oxide primer, or a red oxide finish paint of some sort, or some other paint type completely which is the same colour as traditional red oxide?

[David Schweizer]

1 hour ago, LadyG said:

If I needed a good job done the engine would come out and engine hole prepped, then rust removal, then the tough red oxide as long as it will be undercoat to bilge paint. Or use two pack epoxy. Needs to be oil resistant.

Take technical advice from technical adviser of marine paint suppliers, I don't mean the local marina 

 

When the engine in Helvetia came out for a re-build, I cleaned and de-greased the engine box, after which I gave it two good coats of Finnigans Smoothrite. The manufacturers confirmed that the paint was both heat and oil resistant once cured, and as it was going to be a couple of months before the engind was reinstalled, the paint surface was fine, and had survived both heat and oil after more than ten years when we sold the boat.

[blackrose]

I made the mistake of painting my engine space with Vactan followed by two coats of Rustoleum. The prep was pretty good, it was all taken back to bare metal and my bilges have remained generally dry. However after only a couple of years some areas couldn't handle a bit of condensation and were starting to peel.

 

I'd never use Vactan again for anything and I'd never use any single part paint in an area subject to any significant moisture. Having made the effort to go back to bare steel I was stupid not to epoxy it. 

Edited February 22 by blackrose

[john.k]

I left two unopened drums of red oxide behind at the yard ......another mistake .....my opinion is that traditional red oxide is good is that its porous ............it seems to stop rust for years on sandblasted steel ,out in the open ,yet a scratch does not trap water and cause heavy rusting.

[David Schweizer]

7 hours ago, blackrose said:

I made the mistake of painting my engine space with Vactan followed by two coats of Rustoleum. The prep was pretty good, it was all taken back to bare metal and my bilges have remained generally dry. However after only a couple of years some areas couldn't handle a bit of condensation and were starting to peel.

 

I'd never use Vactan again for anything and I'd never use any single part paint in an area subject to any significant moisture. Having made the effort to go back to bare steel I was stupid not to epoxy it. 

 

I gave upon Vactan very early on, having found that it never seemed to work well as a primer, and started to peel after less than a year. On the other hand I found that both Rustoleum and Hammerite Smooth (formerly Smoothrite) did what it said on the tin. I have a cast iron bench in the garden which I painted with two coats of Hamerite Smooth more than ten years age, Apart from places where the paint surface has been damaged, there is no sign of any rust breaking through.

 

 

Edited February 22 by David Schweizer

[Manxcat54]

Has anyone used or heard anything about AQUA-STEEL Primer and rust inhibitor? it gets good reviews, I am going off Vactan after seeing the comments.

[agg221]

'Red oxide' is literally powdered rust. It is used as a pigment because it is cheap, however it is not of itself very effective as a barrier. Paint consists of the pigment and the binder - what you really want is for oxygen and water to have to work their way round the pigment particles through the binder, because the longer and narrower the path they have to take, the longer the paint holds up. Red oxide is therefore not great because the water and oxygen do not have to work their way around, they can go straight through.

 

Zinc phosphate is a much better pigment, as is titanium dioxide. You can then add colours of your choice to make it look like red oxide.

 

Epoxy is a particularly good barrier and bonds very well to the iron underneath, meaning that oxygen and water have a much harder job displacing it. Polyurethane is an exceptionally good barrier but doesn't bond so well. All of these make excellent paint systems for difficult or very long lasting applications.

 

More recently, epoxies have been blended with siloxanes - this is a matrix which is an even better barrier than standard epoxy and unlike amine epoxies which chalk and dull, polysiloxane epoxies remain with their final finish under UV and weathering so can be used as topcoats. I have found them to have a satin finish rather than gloss, rather an industrial look, but exceptionally durable and probably a very good choice for a bilge.

 

Alec

[dmr]

29 minutes ago, agg221 said:

'Red oxide' is literally powdered rust. It is used as a pigment because it is cheap, however it is not of itself very effective as a barrier. Paint consists of the pigment and the binder - what you really want is for oxygen and water to have to work their way round the pigment particles through the binder, because the longer and narrower the path they have to take, the longer the paint holds up. Red oxide is therefore not great because the water and oxygen do not have to work their way around, they can go straight through.

 

Zinc phosphate is a much better pigment, as is titanium dioxide. You can then add colours of your choice to make it look like red oxide.

 

Epoxy is a particularly good barrier and bonds very well to the iron underneath, meaning that oxygen and water have a much harder job displacing it. Polyurethane is an exceptionally good barrier but doesn't bond so well. All of these make excellent paint systems for difficult or very long lasting applications.

 

More recently, epoxies have been blended with siloxanes - this is a matrix which is an even better barrier than standard epoxy and unlike amine epoxies which chalk and dull, polysiloxane epoxies remain with their final finish under UV and weathering so can be used as topcoats. I have found them to have a satin finish rather than gloss, rather an industrial look, but exceptionally durable and probably a very good choice for a bilge.

 

Alec

 

Interesting stuff, thanks.

I think when most people refer to Red Oxide they are really thinking of Zinc Phosphate primer. Some Zinc primers, like Bondaprimer, are red rather than grey and I suspect this is only because a red pigment is added as older users have fond memories of red lead primers.

Proper red oxide is I assume lead based primer rather than rust particles????

 

.....and I note that red lead powder is still available if you want to make your own lead primer.

I personally think that this is a bit anti-social as a future owner or boatyard might sand it down and not expect to encounter lead.

[TandC]

I've recently used SML Paint's "Bilge Paint" for the inside cabin bilge - it's Xylene-based and dries incredibly quickly.  Two coats applied - easy to roll on and brush into corners.  Looks good and has not chipped or scratched with all the work involved in laying slabs, walking on it, moving timbers etc etc.   Where storm rain came in, the water drained back and pooled for a couple of weeks but did'nt lead to any rust breakthroughs.     Defo a better product than red oxide / blacking which is what I had in previous boat.

 

In the engine bay i've used Jotun epoxy-based Jotamastic 80.   This stuff is very hardwearing and waterproof - and if money had been no object then two coats of that throughout the cabin bilge would have been by option, but SML said it was probably overkill. 

 

[agg221]

14 minutes ago, dmr said:

 

Interesting stuff, thanks.

I think when most people refer to Red Oxide they are really thinking of Zinc Phosphate primer. Some Zinc primers, like Bondaprimer, are red rather than grey and I suspect this is only because a red pigment is added as older users have fond memories of red lead primers.

Proper red oxide is I assume lead based primer rather than rust particles????

 

.....and I note that red lead powder is still available if you want to make your own lead primer.

I personally think that this is a bit anti-social as a future owner or boatyard might sand it down and not expect to encounter lead.

'Proper red oxide' is rust particles. Red lead is a different thing, and a different colour - distinctively orange. It bonds far better and is also a better barrier, therefore gives better corrosion protection. It was always more expensive though. Lead was added to 'red oxide' as recently as the 1970s to improve it but pure red lead paints were also used. We recently had to remove some from a load of gas pipelines installed in the 1960s before we could test the material against hydrogen. The red lead paint was pure red lead, the red oxide contained around 10% lead.

 

Whether a modern paint is 'red oxide' or coloured zinc phosphate often depends on the price - rust is far cheaper!

 

Alec

Edited February 22 by agg221

[blackrose]

3 hours ago, Manxcat54 said:

I am going off Vactan after seeing the comments.

 

Some people have had good results and swear by it, others not so much. I don't think the tannic acid component of Vactan is the issue, but what's in doubt is the water based polymer matrix that it's mixed with. Like David said, I don't think that polymer is a suitable long- lasting primer. If you're going to use a rust converter, Fertan is more work as it needs to be washed off, but I think it's better as it's not being used as a primer.