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Painting Galvanized Metal

Posted by vic99 (My Page) on
Thu, Jan 26, 06 at 13:59

What's the best way to paint galvanized metal(exterior)? What are the best products?


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RE: Painting

Galvanized Metal
Here in UK we use a paint called Calcium Plumbate as primer

Then use ordinary undercoat followed by gloss or whatever

Hope this helps

cog


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RE: Painting Galvanized Metal

vic99
Here in the US, many welding supply distributors carry a spray paint product called Cold Galv. I think is also available in gallon cans for larger jobs. Not sure what your application is?
wiredheart


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RE: Painting Galvanized Metal

wiredheart:

I will be painting galvanized bollards(new). Final coat color will be yellow. Any additional advice will be appreciated.
vic99


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RE: Painting Galvanized Metal

vic99 - Do a GOOGLE search as follows
painting galvanized metal
The first item you see should be by a company called PPG. Go to that site and it will tell you what to do.
wiredheart


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RE: Painting Galvanized Metal

Galvanized metal has a greasy, oily coating to protect it during storage/shipment. This must be removed before it can be painted. Additionally, some sources recommend letting the galvanized surface age before painting it.

Rustoleum carries a latex-base primer that is supposed to be best for galvanized or aluminum surfaces. I am not sure if it is necessary to use a latex top coat, or if this particular application would take a more traditional oil-based enamel.

I have used Rustoleum Red Primer (lead-free) followed by Rustoleum Gloss Black Enamel on weathered and/or once primered flashings and such on my roof. I let the Red Primer weather for a couple of weeks in the summertime to enhance the result. It seemed to work ok, but being on the roof the work doesn't get very close inspection. From the ground, it looks fine.


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RE: Painting Galvanized Metal

Use Ospho, a phosphoric acid solution, to etch the coating, follow the instructions. Then use epoxy paint for a durable finish. I like Ameron 400 because I can use it in small quantities as the mix is 1:1

Thierry


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RE: Painting Galvanized Metal

My elderly neighbor told me just to wipe down the metal with vinegar and then prime and paint as usual.

I haven't tried this yet so you need more input. But, if it works it is a very cheap.


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RE: Painting Galvanized Metal

Can someone confirm that wiping down galvanized steel with vinegar and then painting will work? Can someone who's actual done this comment? I need to pain this steel solar structure that was installed in my backyard!


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RE: Painting Galvanized Metal

There's no harm in trying vinegar as your "mild acid". But first you must remove the oils and greases. The Holy Grail of metal cleaning is to get the metal to the point where "water has no tendency to bead." This mysterious state is very difficult to achieve by ordinary means. Orange oil will work, but NOT if it contains dyes as is usually the case. Hydrocarbons like acetone, BBQ fluid, gasoline (not!) are often recommended, though you may need some lite work after because they, too, often have dissolved oils. I finish (and start, in fact) with a "heavy duty degreaser" meant (I think) for restaurant grills based on 2-butoxyethanol. It;s cheap, like $7 a gallon. But regardless of the chemicals, the elbow grease required is also substantial. And the parts must not be touched with bare hands or with contaminated gloves. Also, any exposed steel will start to rust immediately after being cleaned in this way: watch out for threads if treating pipe fittings, consider greasing the threads immediately after drying. Once clean, the preferred acid is phosphoric. This is available as a wide range of products, meant for etch prepping galvo and many other uses. It's very cheap on a large scale, but you get reamed to one degree or another in gallons and less. I only needed a little, and found a dusty old 32 Oz. bottle of "rust remover" for $4.99. It was quite strong at %50, when I cut it 3:1 I had a gallon of 12.5%. It's not hard to pay $15+ a gallon for the brand name stuff. Any concentration in the range of %5-20 is commonly used.
Figures of 5-15 minutes are usually given. For a large project, I'd use a low concentration and apply with a new (and degreased) all plastic, all poly sponge mop. The low concentration will give you time to assess what's going on before things get out of hand, and time to zap any drips onto inappropriate materials with the garden hose/sprayer. You don't need to neutralize it, but you do need to rinse it off thoroughly, don't let it pool or get into any holes/pipes/connector threads. How to know when to stop depends partly on the original finish. For thin, shiny electroplate as on "zinc plated" fasteners, remove immediately upon discoloration to grey: it may only take seconds. For sheet metal with a checkerboard appearance, you can use your finger in glove. Initially the (wet) surface will feel smooth. After a few minutes you should notice a significant change in texture, like fine sandpaper, or at least feel _weird_. When you start thinking to yourself "Hmmm! This is really doing something!", you can probably stop there, or let it go on about as long again. At least four things make phosphoric acid a good choice. It's biodegradeable, it doesn't fume, it's non-poisonous (used in food), and it won't eat through your concrete, much. But more interestingly, if it should happen upon some (iron/steel) rust, in theory it will convert the rust to a more passive, primeable, paintable surface compound that resists further corrosion. There are limits to it: the acid attacks the steel directly, and converts it more as an afterthought. So if it contacts the steel accidently, rinse it off immediately. Should a bit of rust form later before you get a chance to paint or oil it, a rub-down with the acid and a good rinse after is better than painting rusty metal. Oh, and for hot dipped galvanized? Cleaning is doubly hard: check the flammability and volatility of your degreaser, get it hot if suitable, and stew the parts for an hour or so. Small parts I sometimes submerge, when I'm satisfied it's had a good scrubbing bubble and appears a few shades lighter than at the start I rinse. For poles and conduit, I slop it on and rub it back and forth. up and down with a sponge, until it looks and feels right. Do you have to be so thorough and methodical to successfully paint galvo? It probably depends on how you define success. But in general, it's details like these that make the difference between a good, fair, or fail result by DIY'ers. Some people get the knack real quick, others seem to struggle forever. When it comes to surface treating, electroplating, and electropolishing of metals, the importance of proper cleaning can't be overemphasized. You should wear gloves and eye protection when doing any of this stuff: and while at low concentrations phosphoricic acid may lead to a bit of phosphate "blooming" of plant life, at the concentrations I've mentioned or with associated rinse water you should definitely expect it to burn your lawn.


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