farmershort
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Is undercoat not just a first coat of top coat?
Red Oxide Primer. The Big Questions.
- Thread starter Bobsticle
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aaronmorris
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Yeah, so I'm confused now.
So what should we be looking for in a good undercoat?
So what should we be looking for in a good undercoat?
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Seems to be an unhealthy lack of undercoat talked about chaps.
Prime....... Undercoat.........Topcoat.......
Its a system used for the last 200 years for a reason..............
why undercoat a chassis?
the primers act as an undercoat for this purpose.
the only reason i could see for undercoating is to give a really smooth finish.. but it's a chassis battered by stones
In the mid 40s when my old man was apprenticed into the family painting company his first job was to take the bus to the local paint suppliers and bring back (in 14lb consignments) semi prepared oil paint. If he was polite the chap in the shop would wrap the wire handles in lining paper so they didnt take his fingers off on the way home.
The lead content was that high it used to putty up in the bottom of the cans and on his return to the yard the old boys would roll their sleeves up and kneed the lead back into the oils before even thinking about using a stick. Needless to say none of them had any hair or teeth and the poison would send them a strange colour.
It was then used to make paint by mixing it with oils, dryers, dyes and spirits In various combinations depending on its use. Primer, undercoat, topcoat, timber, steel etc etc. This is how they did it before DIY. One of the reasons a painter had a 7 year apprenticeship.
Primer for instance must be made slightly more oily and much thinner than undercoat. It has to go on fast and be cheap.
The problem with bare steel was, even if you got a coat of primer on it before it began oxidizing, within hours of becoming damp the tell tail signs of rust coloured blotches would start to seep through the porous primer. It wasnt until the undercoat and top coats sealed the steel that the bleed through stopped.
Thats why they they coloured it with oxide pigment. It didnt add anything to the paint apart from colour to hide the bleed. That way a steel beam could be lashed in and sent on its way and it still looked new when it arrived on site. The lead content was controlled by the painter and it wasnt cheap so very little was used.
Later when suppliers and shops began selling ready made paints, red lead was fantastic. It had a high lead content but was expensive compared to simple primers. Because of this industry tended to stick with red oxide primer. That is, simple primer in rust colour.
It makes me smile when people say Oh yea I took it right down to bare metal and gave it two coats of red oxide and a coat of ______?
So you blathered on a couple of layers of the cheapest porous crap available, missed out an undercoat system and hoped the top coat would do all the hard work.
Priceless.
And this makes you an eggspert on red oxide primer? Because of some old story of woe from the 40's?
Why reach for red oxide primer?
Red oxide reacts with iron and iron oxides to form insoluble compounds called plumbates, in which lead is part of the anion, (PbO₃
⁻². For instance, ferrous plumbate has the formula Fe(PbO₃, in which the cation is Fe⁺². That's why I and most other people who need to protect iron or steel from rust reach for it, I've got steel painted in it for 8 years now, the steel was rusty to begin with, its still just as it was the day I painted it , without a top coat.
jamesmartin
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And this makes you an eggspert on red oxide primer? Because of some old story of woe from the 40's?
Why reach for red oxide primer?
Red oxide reacts with iron and iron oxides to form insoluble compounds called plumbates, in which lead is part of the anion, (PbO₃
ehow ?
Bobsticle
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The formula of an undercoat is individual. Its nothing like primer and nothing like top coat.
Its not only a chassis that is steel. I started the thread to evoke thought into paint systems and why none painters like tin bashers and wood butchers think up their own reasons for painting a certain way. You only have to look at the DIY world of one coat paints. People love to take short cuts but in reality they end up having to second coat because the one coat doesn't work.
A primer coats job. Cover and flow into nooks and crannies. Adhere to the work surface to support other coats. Stabilise loose particles not able to be mechanically removed. Dry in a way so as not to need heavy preparation for other coats.
Undercoats job. Seal work surface. build and fill imperfections so further coats require less work to cover and adhere. Be soft enough to make fine sanding and further preparation easier than hard finishes. Supply a slightly softer foundation for brittle finishing coats to act as a buffer for impact and reduce chipping.
Top coats job. To look pretty. To slow deterioration and give longevity.
Its not only a chassis that is steel. I started the thread to evoke thought into paint systems and why none painters like tin bashers and wood butchers think up their own reasons for painting a certain way. You only have to look at the DIY world of one coat paints. People love to take short cuts but in reality they end up having to second coat because the one coat doesn't work.
A primer coats job. Cover and flow into nooks and crannies. Adhere to the work surface to support other coats. Stabilise loose particles not able to be mechanically removed. Dry in a way so as not to need heavy preparation for other coats.
Undercoats job. Seal work surface. build and fill imperfections so further coats require less work to cover and adhere. Be soft enough to make fine sanding and further preparation easier than hard finishes. Supply a slightly softer foundation for brittle finishing coats to act as a buffer for impact and reduce chipping.
Top coats job. To look pretty. To slow deterioration and give longevity.
farmershort
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Which is all interesting an everything, but what most of us want is a tried, tested, and proven system that we know will take care of our landies. Photo evidence is good too!
No, I used a brush.
Seriously , I was well surprised to see it lasting as long as it has done.
And some , perhaps not all , will neutralise any oxidisation and prevent more from appearing.
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blah, half rubbish. cba even talking about it
Turboman
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manor zinc rich is more than that
Manor Zinc Rich Primer
I don't think you need to go nuts on a farm building tbh.
i do fancy trying Electrox | Zinc Rich Corrosion Protection Spray next or their repair patch kit
The site of these steels is very wet, and it is a very salty environment, West facing coast. So the metal needs good protection. Shed upcountry a couple of any primer is fine. Unprotected mild steel here just dissolves!
Also, time is critical, I need to shore up the sheds to use them, before they come down
So I was hoping to get some good stuff, two coats and drying time, and get them up!
Going to the teamac place tomorrow.
Bobsticle
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And this makes you an eggspert on red oxide primer? Because of some old story of woe from the 40's?
Why reach for red oxide primer?
Red oxide reacts with iron and iron oxides to form insoluble compounds called plumbates, in which lead is part of the anion, (PbO₃
No expert nob. Any primer does the same to varying extents. Plumbate primer out performs a large percentage of red coloured primers. Its a shame you cant see the if the steel is oxidizing or not reaching for the red stuff. And yes it will be just the same as it was 8 years ago. Still rusty underneath
farmershort
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Jesus... Can we stop exhalting the virtues of crap with lead in it.... I know... Let's paint with radium rich paint... It'll be a cleaner death!
You rosey eyed old buggers... Lol
You rosey eyed old buggers... Lol
Turboman
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Careful prep, two of the best metal based primer you can get, two topcoat works well for me, and has done for decades. I spray Dinitrol inside.
Pic of the chassis in Members Vehicles, I think. It is twenty five years old, and never welded forward of the rear axle.
Bobsticle
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The site of these steels is very wet, and it is a very salty environment, West facing coast. So the metal needs good protection. Shed upcountry a couple of any primer is fine. Unprotected mild steel here just dissolves!
Also, time is critical, I need to shore up the sheds to use them, before they come down
So I was hoping to get some good stuff, two coats and drying time, and get them up!
I was talking to one of the Clerk of Works in Blackpool recently. The marine grade stainless steel bollards fitted on the front a few years ago are rusting... I feel your pain.
Just as a side note if your painting motorway bridges you sand blast for an hour then paint. No steel is to be left bare for longer than this as the rusting process has already begun and will carry on under the finish.
Bobsticle
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Love it............. :hysterically_laughi
Turboman
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I was talking to one of the Clerk of Works in Blackpool recently. The marine grade stainless steel bollards fitted on the front a few years ago are rusting... I feel your pain.
Just as a side note if your painting motorway bridges you sand blast for an hour then paint. No steel is to be left bare for longer than this as the rusting process has already begun and will carry on under the finish.
Yes, my mate lives in Blackpool, Pompey on the forum, and it is pretty salty. Not so bad as here, they get the protection of Ireland.
Not painted any bridges myself, but another friend has a contract painting company, and they paint all manner of interesting stuff.
Turboman
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Good plan!
Miss the old radium dial alarm clocks, used to glow all night!
And you could get a good tan if you slept close enough to the clock!
Bobsticle
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farmershort
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Which is already being done to my new chassis..... But I want morrrre!Hot Dip Galvanising................
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