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Old 26th Aug 2015, 2:12 pm   #21
JacKam_
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Default Re: How do I put a durable, protective coating on zinc plated steel

15 years ago I built a water distiller for my father in law, we have 500 plants vineyard in Poland. Section steel, welded, 50[l] beer keg, rectifier column, cooler, automatics, all 180 cm high.

I painted it with "Minia" - Pb3O4 suspended in line seed oil. After 1 day I painted the frame with alkyd finish (not sure, polish:emalia ftalowa) paint.
The finish after 15 years is still hard, nice looking, despite of keeping it in a shed.

If anyone wants to try that - let me know. Minia undercoats for bare steel paints are still available in Poland

Thanks,

Jacek
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Old 26th Aug 2015, 4:57 pm   #22
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Default Re: How do I put a durable, protective coating on zinc plated steel

My (very) old tin of Hammerite (Black gloss) was made by "Finnegans", rather than its present owners, Azko Nobel. In view of the comments above, I don't suppose the special solvents are readily available any more.

I can vouch for the effectiveness of lead based paints: I treated the badly rusted steel windows of our bathroom and kitchen with the now unobtainable "Magnet" Calcium Plumbate primer to BS3698 more than 30 years ago and there has been no trace of corrosion returning since. I understand that it is necessary to use boiled linseed oil for traditional DIY paint formulation: ordinary linseed oil will not dry properly. I now top up my part-used traditional oil based paints with some boiled linseed oil after use and it does reduce or prevent skinning without affecting its performance.
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Old 26th Aug 2015, 5:18 pm   #23
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Default Re: How do I put a durable, protective coating on zinc plated steel

I had a tin of their old thinners and it's a different smell to the newer brew. We painted our garage doors (steel and already had 2 coats on) which were slightly rusty in places. Cleaned the rust off then treated with a rust preventer. Primed the spots with a special yellow coloured primer that I can't remember the name of. Then 2 coats of the current Hammerite. Just had the doors replaced as the rust was coming through again after 3 years. Definitely not as good as thew original paint.
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Old 26th Aug 2015, 11:08 pm   #24
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Arrow Re: How do I put a durable, protective coating on zinc plated steel

Quote:
Originally Posted by emeritus View Post
. . . noticed for the first time that you are instructed to only use a special Hammerite solvent for cleaning brushes. You are specifically instructed not to use white spirit or cellulose thinners.
Yes, the Hammerite 'special solvent' will thin Hammerite paint and clean any tools that you've used during the painting process. But it's expensive. I use acetone - which is a lot cheaper and readily obtainable from Sallys hairdressing supplies and which works admirably - and it is a lot cheaper!

Al.
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Old 27th Aug 2015, 12:17 am   #25
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Arrow Re: How do I put a durable, protective coating on zinc plated steel

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Originally Posted by paulsherwin View Post
Al, glad you have no problems using acrylic spray cans - but that doesn't seem to be the common experience, and it's certainly not mine. It does depend on what you're trying to paint though.
The standard problems with domestic aerosols are sagging and orange peeling.
Correct preparation of the material to be painted, getting the correct air temperature and simply using an appropriate technique are the three main requirements. The commonest cause of sagging is holding the can nozzle too close to the surface to be painted, putting on too much paint at 'one go' (over-enthusiasm), or having the target surface not horizontal: this is important: spray painting vertical surfaces will nearly always produce sagging and runs.

I have found that the best method is to choose a day when the air is moderately warm (do the painting outside!) and with a very slight air movement. Keep the surface to be painted horizontal, hold the can about six to nine inches from the target surface and move the can fairly swiftly and repeatedly from left to right, and not going right-left-right-left, ad nauseum. Aim to put a thin coat of paint on - if you can still see a slight trace of the unpainted surface showing through, do not apply any more paint - that will lead to sagging. Leave the item alone for at least half-an-hour. Rotate the object through 90 degrees. Then repeat the above process. Then repeat again. After about 3 to 5 coats, the density of the applied paint should be sufficient to have blocked out any traces of the original unpainted (or painted) surface. Now leave the item alone for about 6 hours (or more) before handling or further treatment. (The paint may be 'dry', but it won't be 'set', after about half-an-hour). If outside, a dust cover over the item (such as a cardboard box with one side removed) is a good idea at any stage when you are waiting for the paint to dry.

Six further tips.
1. A common cause of a spoilt finish are drips of paint from the aerosol nozzle. Occasionally spray a little paint away from the target and wipe the nozzle with a clean rag (preferably using a little acetone on that rag) to prevent those drips landing on the target surface and to keep the nozzle clean.
2. Always shake the can prior to use and occasionally shake the can during the painting process. (Do that away from the target surface).
3. The unpainted surface to be painted must be spotlessly clean and especially free from any traces of oil or grease - so having thoroughly cleaned it, handling and fingering it is a no-no. If the surface is painted, it will greatly help if that surface is either stripped of the old paint first or failing that, is sanded down to a very smooth finish. Then make sure all traces of dust are removed and that it is clean and de-greased.
4. Overall, do not hurry that painting job! It's very easy to get carried away with the aerosol and end up applying too much paint in one go. That will produce sags, uneven density of finish - and takes much longer for the last coat to dry - and set - anyway.
5. For cleaning up afterwards, I use acetone: the commercial variety is quite adequate, but 'nail varnish remover', commonly sold in small bottles, isn't - it's far too dilute. (Aside: acetone is useful for many things - including thinning 'Tippex', Hammerite and as a general degreaser and 'muckite' remover).
6. If painting steel and if it has rust spots, treat the rust with 'Jenolite' (or something similar - e.g. a phosphoric acid based chemical) to stabilize the rust first.

I've used 'car aerosol paints' on all manner of materials: steel (raw, cadmium or chromate plated), aluminium, wood, Bakelite and 'plastic' with acceptable successes. Occasionally, some of those materials had been previously painted with 'white spirit' based paint, cellulose paint and even Hammerite.

► None of that above is intended to be an absolute lesson in how to use aerosol paints. It is merely what I have found works for me. I'm sure that there will be others here who can add various do's and don'ts to achieving an acceptable result with commonly-available aerosol paints.

HTH,

Al.

Last edited by Skywave; 27th Aug 2015 at 12:28 am.
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Old 27th Aug 2015, 7:33 am   #26
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Default Re: How do I put a durable, protective coating on zinc plated steel

One other tip I'd add:

Start your left to right spray pass off to the left of the work, far enough that you can get your hand up to a stable speed and the button pressed, so that a stable spray moving at a stable speed is passed across the work with the nozzle a constant distance from the work, and spraying always perpendicular to the work.

Keep the movement going and the spray going until after you've passed beyond the right hand end of the work.

This gives you a uniform application, you don't get thicker coverage at the ends where your hand is accelerating and decelerating.

Hold the can, practice your moves without pressing the button until you're happy that you can scan the work with the nozzle perpendicular at a constant distance from the work and at a constant speed.

Professional sprayers make a lot of practice moves over a surface to be painted to get the 'feel' of following shapes and how far they have to stretch to cover the job before ever trying to apply any paint. Using a spray gun on challenging shapes, you do passes with air but not paint on so you can sense where reflections are going to go.

I learned to spray on things a bit too big to be able to always paint onto horizontal surfaces.

Sprayed paint doesn't fill any surface defects. The uniform colour makes them more visible. Your preparation has to be excellent before your final coat. So do your prep, spray on enough coats of colour to be opaque and check for imperfections. Use stopper (fine detail filler) allow a day to harden, then use 600 or finer paper wet, to get a good finish.

Doing wet rubbing with fine grit paper is easier and produces a better finish if you rub a bit of soap onto the wet paper from a bar of cheap hard soap.

Rubbing blocks are needed to keep flat things flat. Hands are good for curves (Palm of hand used as a pad) Applying pressure with fingers tends to make finger spaced ripples.

Time spent spraying is trivial compared to time preparing.

David
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Old 27th Aug 2015, 8:01 am   #27
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Default Re: How do I put a durable, protective coating on zinc plated steel

Direct to metal paints are best applied with a gloss roller, paintbrushes are only
useful for inaccessible corners etc. Two coats are required, and allow up to 4 weeks
to dry with the high VOC paints. Finish quality is a good as aerosols.
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Old 27th Aug 2015, 9:25 am   #28
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Default Re: How do I put a durable, protective coating on zinc plated steel

Skywave and Radio Wrangler's most recent posts make an excellent primer for spraying technique in general.

When spraying radio cabinets for Radiocraft customers I would add only one coat a day. Typically, including preparation the process would take at least two weeks.

Steve
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Old 27th Aug 2015, 9:31 am   #29
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Default Re: How do I put a durable, protective coating on zinc plated steel

Also - when spraying be observant of what the paint manufacturer says about re-coating: typically you can put on several coats at short (10 minute) intervals, or you have to wait a much longer period [at least a day, sometimes up to a week] before re-coating.

Getting this wrong can cause a solvent reaction between the older and newer coats that looks like a screwy version of the 'wrinkle' finish used on WWII-era HROs etc.


I like to use an etch-primer on prepared bare metal: a very thin 'misting' - barely enough to actually conceal the colour of the underlying metal - of a Zinc Chromate primer (available in aerosol cans from most aviation suppliers) will give really good adhesion for the subsequent coats. This particularly applies for aluminium and its alloys, and cadmium or zinc-plated surfaces.

Have a ok here: http://www.lasaero.com/site/products...y?id=U03IO07X1 for some options.

Getting paint to adhere to Stainless-steel is an entirely different game - ask John DeLorean!

Last edited by G6Tanuki; 27th Aug 2015 at 9:42 am.
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Old 27th Aug 2015, 9:31 am   #30
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Default Re: How do I put a durable, protective coating on zinc plated steel

I like Hammerite and have been using it a lot lately. I can't say I have noticed any change in its formulation - it is still high in VOCs which causes me a lot of trouble as the wife gets migraine attacks if the fumes get near her.

But the hammerite "smooth" range has only limited colours so I have taken to mixing them to get the colours I want and it seems to work OK. I note that Hammerite themselves are offering colour-matching at some outlets but I have not found anyone who does it yet.
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Old 27th Aug 2015, 11:47 am   #31
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Thumbs up Re: How do I put a durable, protective coating on zinc plated steel

David - your post #26 makes an excellent supplement to mine, post #25 - thanks.

Al.
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Old 27th Aug 2015, 12:27 pm   #32
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Default Re: How do I put a durable, protective coating on zinc plated steel

Al and David's posts give excellent advice.

I should make it clear that I do use acrylic aerosols, and sometimes even achieve good results, but I'm old enough to remember car paint before acrylic took over and there's no denying that acrylic is more difficult to use.
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Old 27th Aug 2015, 1:11 pm   #33
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Default Re: How do I put a durable, protective coating on zinc plated steel

Thanks to all for very useful and informative posts. I do happen to have a litre of Acetone that I will try out with my old Hammerite. I got some in France when visiting a relative: Acetone is readily available in French supermarkets and Bricomarchés as a cheap household cleaner, along with alcohol.

Nice to know that Zinc Chromate primer is still available if you know where to get it. Its use in aviation probably clears up a suspicion I had on a works visit to the old BOAC depot at Heathrow when they had just received delivery of their first Jumbo Jets. They had been delivered as empty shells and were being kitted out, and much of the bare metalwork was painted in what looked to me very much like the yellow ZInc Chromate primer I was using on my car.
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