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rcx822
Joined: 31 Dec 2010 Posts: 112
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Posted: Tue May 31, 2016 12:38 pm Post subject: Metalwork/rust treatment |
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I've read a few posts and articles on dealing with rust already, but if anyone can point me to any more good ones I'd be grateful.
With using phosphoric acid to remove rust, is there any way of thickening it or using an alternative, so that it can be used on vertical surfaces and small areas that could be done "in situ" ?
When treating inside of box sections, so I understand that there's no way to clean and derust in there? So are the anti corrosion agents really strong enough to stop the spread of rust if they are blindly sprayed on uncleaned surfaces that may already have flaking paint or surface rust in there? Maybe it depends on how bad things are in the box sections?
I always thought that rust had to be entirely removed to stop it spreading but somehow all these classics are being preserved when I'm sure they all have box sections that rust from the inside.
I looked at e-coating but there's quite a few posts online saying that seams would start rusting just a few years after e-coating. I also think there's only one plant in the UK and they have a 135cm height limit which I'm well above. |
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Phil - Nottingham
Joined: 01 Jan 2008 Posts: 1252 Location: Nottingham
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Posted: Tue May 31, 2016 6:19 pm Post subject: |
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If anyone found one that worked it would be suppressed. Bare and even new steel has inherent tendencies to rust any post manufacturing application is doomed to failure especially in the damp & wet UK
Modern cars (=2000 on) have really excellent paint protection that stops the wafer thin steel corroding. A modest chip/scratch in its tough but flexible coating leads to rapid corrosion although with less tendency to creep underneath but it will do eventually. Older cars have much greater thickness but far inferior, if any at all corrosion protection
In the 50 years I have tried everything - the best way is too cut out corroded steel and replace with new. This still will rust however - I ham on 3rd & 4th times repairs with either method _________________ Rover P2
Rover P4
Rover P5 & P5B
Land Rover S2 & S3
Morris Mini Traveller Mk2 |
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MikeEdwards
Joined: 25 May 2011 Posts: 2479 Location: South Cheshire
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Posted: Tue May 31, 2016 7:10 pm Post subject: |
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I've read that mixing phosphoric acid with wallpaper paste can be a good way to make it work on vertical surfaces, but I've never tried it. One of the packaged products comes as a gel, that worked quite well for me but I can't remember the name of it. |
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Bitumen Boy
Joined: 26 Jan 2012 Posts: 1737 Location: Above the snow line in old Monmouthshire
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Posted: Tue May 31, 2016 7:28 pm Post subject: |
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MikeEdwards wrote: | I've read that mixing phosphoric acid with wallpaper paste can be a good way to make it work on vertical surfaces, but I've never tried it. One of the packaged products comes as a gel, that worked quite well for me but I can't remember the name of it. |
One thing that does work is using it to stick tissue paper to the panel - just with the wetness of it - then building up the thickness as necessary. Cheapy loo roll or similar works fine. |
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Lanchester 1953
Joined: 05 May 2016 Posts: 34
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Posted: Wed Jun 22, 2016 9:57 pm Post subject: |
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put some phosphoric acid in an old hand spray gun like a bug spray for plants and squirt it as a mist. You can also use an air pressure spray to blow it inside panels, chassis sections, doors etc. Then either paint over or spray with Waxoil, or any other sealant. |
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Miken
Joined: 24 Dec 2012 Posts: 544
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Posted: Tue Oct 18, 2016 8:22 pm Post subject: Rust treatment (yet again) |
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This may be of interest.
I found this picture of a bit I cut off and discarded from my old Morris when I was renovating the front wings. You can see that part of it has been shot blasted'
Before I cut it off, the entire wing was sprayed with this product:
http://www.frost.co.uk/por15-prep-metal-ready.html
Normally shot blasted steel will, quite literally, rust before your eyes if you take it outside on a damp day. I found this off-cut in my garden where it had lain in all weather (admittedly it was summer) for about 7 weeks. There is hardly any new rust formed on the blasted area apart from the edge where I hack sawed it off. Apologies if this sounds like and advert, but I was genuinely surprised and please to find the part had been protected so well.
Mike
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rcx822
Joined: 31 Dec 2010 Posts: 112
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Posted: Fri Oct 28, 2016 1:18 pm Post subject: |
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Quote: | This may be of interest.
I found this picture of a bit I cut off and discarded from my old Morris when I was renovating the front wings. You can see that part of it has been shot blasted'
Before I cut it off, the entire wing was sprayed with this product:
http://www.frost.co.uk/por15-prep-metal-ready.html
Normally shot blasted steel will, quite literally, rust before your eyes if you take it outside on a damp day. I found this off-cut in my garden where it had lain in all weather (admittedly it was summer) for about 7 weeks. There is hardly any new rust formed on the blasted area apart from the edge where I hack sawed it off. Apologies if this sounds like and advert, but I was genuinely surprised and please to find the part had been protected so well.
Mike |
Thanks I took a look at this product. I've read about zinc phosphate, which this uses, it's used as temporary rust prevention. I'd be interested if it's presence adversely affect the adhesion of the primer that would then go on top.
In the end I've decided to go with Jotun epoxy primer and topcoat. It's similar to Epoxy Mastic 121 but much cheaper as it's sold for industrial purposes. Only problem is that manufacturer says it should be applied by airless spray which is a problem as airless sprayers can't have the spray coverage set low and have big hopppers so are no good for painting car parts that are relatively small. But people are ignoring this, thinning it out, and applying with a LSPV spray gun set to 50psi (i.e. double what LSPV should use), which appears to work. |
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colwyn500
Joined: 21 Oct 2012 Posts: 1745 Location: Nairn, Scotland
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Posted: Fri Oct 28, 2016 8:18 pm Post subject: |
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[quote="rcx822"] Quote: |
Only problem is that manufacturer says it should be applied by airless spray . |
In most applications it's actually better to apply epoxy by brush because it needs a relatively thick coating in order to allow it sufficient time to cure. It also allows the paint to be pushed into awkward areas or crevices.
Airless allows high volumes and minimal thinning.
Thinners obviously make it spead thinly with the risk that it will simply dry by evaporation before it gets the chance to cure and properly bond tothe metal surface. |
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rcx822
Joined: 31 Dec 2010 Posts: 112
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Posted: Fri Oct 28, 2016 8:50 pm Post subject: |
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colwyn500 wrote: |
In most applications it's actually better to apply epoxy by brush because it needs a relatively thick coating in order to allow it sufficient time to cure. It also allows the paint to be pushed into awkward areas or crevices.
Airless allows high volumes and minimal thinning.
Thinners obviously make it spead thinly with the risk that it will simply dry by evaporation before it gets the chance to cure and properly bond tothe metal surface. |
Finally an explanation why they don't recommend air spray!
What if I brush on and then sand smooth before top coat? I tried brush but the finish showed brush strokes. Jotun says topcoat can be sprayed. |
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colwyn500
Joined: 21 Oct 2012 Posts: 1745 Location: Nairn, Scotland
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Posted: Fri Oct 28, 2016 9:59 pm Post subject: |
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rcx822 wrote: |
What if I brush on and then sand smooth before top coat? I tried brush but the finish showed brush strokes. Jotun says topcoat can be sprayed. |
It is impossible to brush on the epoxy without it dragging and leaving brush-strokes. It is also very important to give it at least two coats and the second needs to be done relatively promptly, say withing about 12 hours of the first. This is because if the curing process goes on for too long, an external layer will prevent full adhesion. This applies equally to any additional coats of conventional air-drying paint that you obviously intend to to put over the epoxy.
So sanding out any brush marks is a good idea because it also breaks down that layer allowing the next coats to adhere properly. The sanding should be done imediately prior to overpainting otherwise a new, cured coat will form.
I would go with a relatively light sanding with something like 320 grit and use a good high-build primer to take out any remaining imperfections. Apart from the fact that epoxy is not the best product to sand down, there is the risk that you may oversand the epoxy and reduce its effectiveness.
I have found that over most of my car body which was painted with epoxy over bare steel treated with phosphoric acid and then wiped down with a "desalting" liquid, it is almost as if it hs been galvanised.
I used a conventional spray but with a big nozzle and just enough of the correct No. 17 thinners to get it out of the gun. |
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rcx822
Joined: 31 Dec 2010 Posts: 112
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Posted: Sat Oct 29, 2016 9:05 am Post subject: |
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Good sounding advice Colwin. How did you learn this?
I bought the winter grade paint as it gets cold some nights. Winter grade can be applied in colder conditions. Also got ano infrared heater and connecting it to a thermostatic switch to keep the temp above 10 degrees. |
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colwyn500
Joined: 21 Oct 2012 Posts: 1745 Location: Nairn, Scotland
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Posted: Sat Oct 29, 2016 3:57 pm Post subject: |
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rcx822 wrote: | Good sounding advice Colwin. How did you learn this?
I bought the winter grade paint as it gets cold some nights. Winter grade can be applied in colder conditions. Also got ano infrared heater and connecting it to a thermostatic switch to keep the temp above 10 degrees. |
I'm good at reading product information sheets and there is a lot on the "Rustbuster" website.
I also found that experience backed up all of the directions and I did make the odd mistake at first. |
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rcx822
Joined: 31 Dec 2010 Posts: 112
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Posted: Sat Oct 29, 2016 4:17 pm Post subject: |
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I read the Jotun application guides and it didn't say a lot of that though. Rust busters don't have an application guide at all! No specification on time between coats, min temperatures etc. They seem a lot more casual about it. That's why I went for Jotun, they are far more specific and also much cheaper.
Rust busters did say that their Epoxy Mastic 121 can be heated to thin it. I'm thinking of buying one of those little single electric pods, could use it to heat paint and also for heating caustic soda for decreasing small parts prior to zinc plating or painting. |
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colwyn500
Joined: 21 Oct 2012 Posts: 1745 Location: Nairn, Scotland
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Posted: Sat Oct 29, 2016 7:30 pm Post subject: |
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rcx822 wrote: |
Rust busters did say that their Epoxy Mastic 121 can be heated to thin it. . |
You did the right thing because I read that Rustbuster may be a repackaged Jotun product anywayalthough i can't verify that I just keep dowloading product sheets to gather info and Jotun are great at that. |
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rcx822
Joined: 31 Dec 2010 Posts: 112
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Posted: Sat Oct 29, 2016 7:42 pm Post subject: |
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Meant to say I'm thinking of getting a mini electric hob to heat paint and for hot degreasing. |
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