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Red oxide paint vs hull blacking


jenevers

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Not sure how effective red oxide paint is underwater. Given a fresh steel hull I would have been tempted to use a fit for purpose product such as International Primocon as the undercoat at least.

I used to use Primocon as an underwater primer before I had the whole lot grit blasted off to epoxy it. It's good stuff and will extend the time between blackings.

 

As for using red oxide, I thought it was common knowledge that as a porus paint it was unsuitable for underwater applications. We've all seen primed topsides of boats that have been left too long and rust has bloomed through the paint. If it has helped to prevent corrosion under the waterline in some cases then it's only because bitumen itself is so poor as an underwater hull coating system.

Edited by blackrose
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OK, my 10 cents worth. Red oxide or almost any primer seems to stick quite well. New steel often comes ready primed with `red oxide` as a holding coat. This needs painting as it is certainly porous and if you don't you will have a big job after a month or so. My boat, brand new with primed steel was painted with a two pack primer followed by two pack epoxy tar (Sigma) . This seems pretty good but where the coating has disappeared the red primer has gone as well. I think there is a lot more yet to be discovered about coatings. The Ironbridge - just up the road from here, has been painted in some sort of grey paint with sparkly bits in it and I would like to do a trial with that on a bit of steel dropped in the water, Bitumen? probably ok with lots of coats. We need a scientific trial, I bet two coats of B&Q white gloss wins.

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OK, my 10 cents worth. Red oxide or almost any primer seems to stick quite well. New steel often comes ready primed with `red oxide` as a holding coat. This needs painting as it is certainly porous and if you don't you will have a big job after a month or so. My boat, brand new with primed steel was painted with a two pack primer followed by two pack epoxy tar (Sigma) . This seems pretty good but where the coating has disappeared the red primer has gone as well. I think there is a lot more yet to be discovered about coatings. The Ironbridge - just up the road from here, has been painted in some sort of grey paint with sparkly bits in it and I would like to do a trial with that on a bit of steel dropped in the water, Bitumen? probably ok with lots of coats. We need a scientific trial, I bet two coats of B&Q white gloss wins.

I've received some advice from a paint specialist about over coating the red oxide on my project boat.

"If the red oxide is oleo resinous or alkyd resin based the film won't be very strong or solvent resistant and when over coated the weak point will be within the red oxide paint film"

So over coating with a high bond strength product means the red oxide will come off with the top coat, as you have experienced.

Traditional solvent based blacking has lower bond strength, but the solvent can affect the red oxide.

Think I'll just go with a relitively low solvent blacking product, if such a thing exists, and see how it goes.

Edited by Eeyore
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Red Oxide Paint is great for corrosion prevention but it's only meant to be used as a Primer, it has a low micron count and is more permiable to water and oxygen compared to top coats such a 2k/Tar based coatings.

 

Tar Based/Epoxy 2k's are currently the best imo.

 

Red Oxide is not a top coat it's a Primer.

 

I've done a bit of work for a North Sea Wind Farm company painting 8ft wind turbine bearings and we only used 1k etch primer followed by 2k primer and 2k topcoats. Imo 2k is the best surface coating for metal surfaces open to the elements at the moment.

Edited by GreyLady
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As said before, using the term 'red oxide' is in my eyes largely pointless, like 'blacking' 'primer' or 'paint' its such a broad and miss used term it could mean anything.

 

Some will be talking about great paint, some will be suitable for use underwater, some will be cheap muck little more use than milk.

 

Without a brand name, spec, or some.other information it tells you only the colour!

 

 

Daniel

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OK, my 10 cents worth. Red oxide or almost any primer seems to stick quite well. New steel often comes ready primed with `red oxide` as a holding coat. This needs painting as it is certainly porous and if you don't you will have a big job after a month or so. My boat, brand new with primed steel was painted with a two pack primer followed by two pack epoxy tar (Sigma) . This seems pretty good but where the coating has disappeared the red primer has gone as well. I think there is a lot more yet to be discovered about coatings. The Ironbridge - just up the road from here, has been painted in some sort of grey paint with sparkly bits in it and I would like to do a trial with that on a bit of steel dropped in the water, Bitumen? probably ok with lots of coats. We need a scientific trial, I bet two coats of B&Q white gloss wins.

There have been plenty of technical trials of different paint systems. The literature is all out there in the public domain.

Red Oxide Paint is great for corrosion prevention but it's only meant to be used as a Primer, it has a low micron count and is more permiable to water and oxygen compared to top coats such a 2k/Tar based coatings.

 

Tar Based/Epoxy 2k's are currently the best imo.

 

Red Oxide is not a top coat it's a Primer.

 

 

And it's not a primer for underwater applications.

I've done a bit of work for a North Sea Wind Farm company painting 8ft wind turbine bearings and we only used 1k etch primer followed by 2k primer and 2k topcoats. Imo 2k is the best surface coating for metal surfaces open to the elements at the moment.

I don't know what 2k is, but I've done a lot of work restoring the hulls of old steel steam boats and in my opinion the best product on the market for the DIYer is the Jotamastic 87 range of two pack epoxies because they're fairly surface tolerant and easy to mix and apply, as well as high performance. You'll still need to grit blast the steel through.

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I don't know what 2k is...

It's another way of saying two pack, typically used in the automotive industry, originally appears to have inferred for defined twopack isocyanate based paint but now appears to be used for anything coming in two pots and requiring mixing before application/hardening.

 

 

Daniel

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Red Oxide is not a top coat it's a Primer.

 

And it's not a primer for underwater applications.

Red oxide that can be used as top coat:

http://www.amazon.co.uk/250ml-Carplan-Genuine-Brush-On-Primer/dp/B00BHYFD3W

 

Red oxide that can be used underwater:

https://www.thepaintshed.com/products/teamac/teamac-metaclor-cr-primer/c-24/c-298/p-816/cs-1494

 

 

 

 

Daniel

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I've never seen red oxide used as a top coat because it is historically known to be pourous to water and oxygen, without seeing the data sheet on the carplan link or using it i can't comment.

 

(Carplan in general is crap)

 

Saying that the few boats I've seen painted with red oxide on their roofs and decks look great. ☺

Edited by GreyLady
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Carplan in general is crap.

Indeed so, my point however is simply that using the 'red oxide' to detail paint spec is false, because it details is the painta colour. Both of the above links where found in 30secs googling on my phone and only very loosely vetted.

 

 

Daniel

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Indeed so, my point however is simply that using the 'red oxide' to detail paint spec is false, because it details is the painta colour. Both of the above links where found in 30secs googling on my phone and only very loosely vetted.

Daniel

I see your point their Daniel, I guess we're all guilty of generalising.

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Indeed so, my point however is simply that using the 'red oxide' to detail paint spec is false, because it details is the painta colour. Both of the above links where found in 30secs googling on my phone and only very loosely vetted.

 

 

Daniel

Except that it doesn't even seem detail the paint colour. The red oxide underwater primer in the link you posted is actually grey.

 

Anyway, you're right that there are a lot of different red oxide coloured paints. I've used Bonda Primer for above water on steel and unlike regular red oxide primer it's alkyd resin based and impervious to moisture. It just happens to have a red oxide colour, but I wouldn't describe it as a red oxide primer.

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I agree the examples are extreme and or somewhat tenuous, and neither well fit the descriptor 'red oxide primer' however I continue to stand by the statement that one red oxide primers performance has no real bearing on the next.

 

 

Daniel

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Even 2 pack high build primers such as sickens/ice and dupont are all porous, I've yet to come across any primer that isn't.

 

When I worked on aerospace parts that i painted they all came with air worthiness job spec sheets Far/Cs, maybe I was guilty in generalising all red oxide brands on this thread maybe because of its reputation of being an old skool coating.

 

I stand by what I say too red oxide primer is not a top coat nor does it have final coat protection qualitys.

 

Daniel I am sure you know Fermec, they subcontracted a lot of JCB work to Richmond Metal Refinishers and I've probably painted 1000s of Hydraulic rams and pipes for JCB in that crap Epoxy yellow they supplied us which does not cover very well.

 

God I hate JCB yellow. Pffft.

 

I've delivered them too which was amazing going inside the JCB grounds. :-)

Edited by GreyLady
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I agree the examples are extreme and or somewhat tenuous, and neither well fit the descriptor 'red oxide primer' however I continue to stand by the statement that one red oxide primers performance has no real bearing on the next.

 

 

Daniel

Yes, I don't think that anyone would disagree with you on that.

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Even 2 pack high build primers such as sickens/ice and dupont are all porous, I've yet to come across any primer that isn't.

 

Jotamastic 87 two-pack epoxy doesn't require any primer. It can go straight onto properly prepped steel, so in that sense I suppose it could be called a primer, but it isn't porous. It can be over painted with Jotamastic Hardtop if required but the Hardtop is mainly cosmetic. After consulting Jotamastic technical support, on my boat I used 2 coats of Jotamastic 87 with aluminium, plus 2 coats of Jotamastic 87 black. I didn't use any Hardtop.

Edited by blackrose
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i still think zinger is best as it is designed for the job ie being underwater the blacking they supplied however has gone silver grey but is tough it takes a serious knock to remove it and the zinger underneath seems to remain intact. whilst it was expensive [the same as 2 pack] i do believe its better but time will tell if i am right or wrong

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I suspect "primer" is now used for any paint (one or two pack) that is designed to stick directly to bare metal (or wood or whatever), so its no longer true to say that all primers are porous, though many are.

Our hull is blacked in a two pack (the one that Midland Chandlers sell). Its data sheet describe it as a primer but so far ite done pretty well.

The "red oxide" thing is of course a lovely bit of history, most good metal primers were based on lead oxide ("red lead") and they did work well.

Metal primers are now zinc oxide and so are grey but the makers add pigment to make them red to please the old farts who remember the real stuff.

 

Another vote for Bondaprimer, its not porous but if used as a top coat it does change colour in the sun. It paints on lovely, dries quick, and looks good.

Did my well deck in epoxy primer then a coat of Craftmaster raddle but it was a bit slippy so I put a couple of coats of Bondaprimer on top!

 

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

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Interesting

I use Rustins (great name eh?)

http://www.rustins.eu/Details.asp?ProductID=791

 

Seems good to me. Anyone else used it?

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I use Rustins (great name eh?)

http://www.rustins.eu/Details.asp?ProductID=791

 

Seems good to me. Anyone else used it?

 

Depends what for!

 

I have sloshed Blackfriers QD90 on the inside of my diggers cab, their red oxide primer (gotta love it) followed by the grey enamel. Went on lovely, really nice finish, hopefully will last well, which the internet suggests it will.

 

Wouldn't use it it on the hull of a narrowboat however, although it might be grand for the cabin.

 

 

Daniel

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Jotamastic 87 two-pack epoxy doesn't require any primer. It can go straight onto properly prepped steel, so in that sense I suppose it could be called a primer, but it isn't porous. It can be over painted with Jotamastic Hardtop if required but the Hardtop is mainly cosmetic. After consulting Jotamastic technical support, on my boat I used 2 coats of Jotamastic 87 with aluminium, plus 2 coats of Jotamastic 87 black. I didn't use any Hardtop.

I read the data sheet on that although it's not a primer as such more of a one coat application it does sound to be good stuff.

 

I still don't care what anyone says red oxide primer is Crap as final coat and well behind the times in protective coatings even just as if only used as a primer, i made the massive mistake of painting a bare metal landrover chassis in it and rust spots bleed after 12 months.

 

 

I will stick to what I trust and been taut.

Edited by GreyLady
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