Cold galvanizing spray? Field applied Galvanized Zinc Coatings?

A. Hi Oscar. Yes, cold galvanizing paint can be sprayed on, or it can be applied as a dip-spin coating. In the USA there are a half-dozen or more brands.

A. I believe that you are indeed looking for an organic/metallic coating. They may be applied by dip-spin, dip, or spray. Some contain only zinc; some have zinc and aluminum. Some use those metals in particle form; some use metals in flake form. They are very effective in achieving high corrosion resistance. There are some makers here in the U.S. There is one I just visited in Europe who does a very creditable job. This process is great for fasteners and small parts.

Sincerely,

A. Hello again Oscar,
If you use the search term "dip-spin coating" in the search engine you will find a number of threads listing the various suppliers of zinc-rich dip-spin coatings. There are about a half-dozen major brands including Magni Group, Metal Coatings International, Doerken, Sermagard, Zintek, etc. ; sometimes they have a licensing arrangement where particular job shops get the exclusive in a given area, and someone may already have taken your area with that supplier ...so you may have to go down the list a bit to find a supplier who can offer their product to you. Good luck.

Regards,

A. We have been using a spray product for some time now. It is a zinc-rich coating which works well on wire-brushed steel. Sincerely,

A. "Cold galvanizing" is probably zinc rich paint. It will not hold up to 400 degree temperatures. Most of the larger paint companies carry a type of zinc rich paint. Does this go on bare steel or is masking an area to be hot dip galvanized to prevent the zinc from adhering? You probably would not want to use this to mask an area to prevent it from being hot dip galvanized.

A. "Cold galvanizing compound" is a zinc-rich paint in spray cans or gallon cans for consumers, but Alvin Products, Clearco Products, ZRC and others offer it for industrial use in larger containers. Some paints will hold up through a phosphatizing and powder coating process so, although I can't guarantee it, I would expect that these cold galvanizing compounds might as well.

A. I don't think it's a great idea, Ramesh. Galvanized nuts and bolts are built to different dimensions to allow room for the thickness of the coating. Even if the coating 'worked', the threads wouldn't fit.

Yes, it would increase the corrosion resistance by some amount, but so would dipping it in chocolate; neither are really proper solutions. Cold galvanizing has application, but not on threaded hardware on top of zinc plating -- just my opinion.

A. Hi, Dana. You are correct that hot dip galvanizing is a factory-applied finish. The metal must be pickled and cleaned, then fluxed before dipping into the molten zinc. And it usually receives a post-treatment with a chromate based chemical. The closest you will get for field application is probably a Cold Galvanizing Compound / Zinc Rich Paint. This is sprayed on like paint, but it is rich in zinc for galvanic protection of steel. Good luck.

Regards,

A. Hi Aziz. There are a half dozen or more brands here in the USA. I'd suggest that you buy one can each of a few brands, and see what you can learn from their list of ingredients and safety data sheets, and their performance as the first step. After that you can investigate the patent situation, which is quite easy today with patents.google.com, and then start in earnest on formulations. Good luck.

Regards,

A. I think that the type of product you are looking for is called a 'wash primer.' A formula (commercial products are available) is given by DOD-P-15328 D. The specification says that it is intended as a bonding coat between the metal (i.e., zinc) and a subsequent paint layer. The wash primer has inhibitive and protective properties by itself, but if you are going to put a coating on zinc, I'd recommend that you follow the DOD's implied advice and follow up with a coat of paint.

A. Hi Harry. Sorry, not really effectively. It can't provide galvanic protection to the underlying steel if it's not in electrical contact with it, and the primer will electrically insulate the zinc from the steel

Luck & Regards,

A. This term "Cold Galvanizing" is a misnomer. It's either galvanizing or it not. If it is, then it's chemically cleaned steel dipped into molten zinc to form an alloy of zinc and iron on the surface of the item. Normally done at about 450 °C, (sometimes hotter), it's known as Hot Dip Galvanizing.

Then there's paint.
Some paint has zinc particles in it, and that improves the corrosion resistance.

You seem to be asking if paint can be applied over paint. Unless the two paint systems chemically react with each other (some do) - so if they're compatible, then you can apply zinc rich paint over a primer. You might need to sand the primer to ensure a good key.

But why would you?
Zinc rich paint aims to protect by adding zinc particles to the resin of the paint. Zinc is known to help prevent corrosion of steel. But corrosion being an electrical process essentially, requires a flow of electrons to help oxygen react with metallic iron to form oxide of iron. Zinc, if electrically connected to the steel will react in preference, being more reactive than the iron, until it's consumed, and then the steel oxidizes. That's how galvanizing works.
But zinc rich paint suffers from the zinc particles not being connected to each other, and in fact suspended in a non conducting resin (paint).
But it's more effective than having no zinc.
The zinc rich paint should probably go on next to the steel, then subsequent coats of perhaps colour (aesthetics), or added protection by adding thickness to the coating system, making a barrier for water and oxygen, attempting to prevent them getting to the steel.

---

Corinthian Leather

There's always a cynic; I bet you don't believe in "Rich Corinthian Leather" either, Geoff :-)

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. For those who wish to investigate these issues more comprehensively, I recommend Charles G. Munger's Corrosion Prevention by Protective Coatings [affil link on Amazon]. His chapter on "Corrosion-Resistant Zinc Coatings" is quite wide-ranging. Among other topics, he discusses how maintaining a high pigment (i.e., zinc) to vehicle ratio produces a conductive, sacrificial deposit.

A. Hi William. I wouldn't expect so ... unless little particles and shards of metal are magnetically sticking to the pipe and you aren't able to remove them before painting.

Regards,