Putting ZRC to the test

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Challenge 27
Posts: 43
Joined: Fri Jan 04, 2019 4:19 pm

Putting ZRC to the test

Post by Challenge 27 »

Am putting up a tv aerial. A neighbor knew of where an old 3 legged antenna tower was that the owner didn't want. Wire-wheeled off all the rust and then coated it with ZRC 10003 Cold Galvanizing Compound (readily available on Amazon.com (what isn't these days!). First time I have ever worked with a cold galvo compound. Used 2 12-ounce aerosol cans for the first coat; but ran out before I was done. Those 12 ounce cans don't cover very much. I then used a quart of the brush-on stuff to finish the first coat, then gave it two more, using up the quart.

As stated the 12 ounce cans didn't last very long. I thought that they were prone to splattering. The first two photos show the results. Have included a Challenge 27 wheel section for comparison.
galvo 1.jpg
galvo 2.jpg
The next two photos show the antenna tower after being coated with paint-on ZRC. The instructions say you don't need to mix it with a bit of thinner but . . . this stuff dries really fast. I ended with a thick gloppy finish. Not so pretty but hopefully it will last in the galvo-eating climate around here. Some thinner (mineral spirits) might help it spread more evenly. I would recommend using a shady spot to do any painting.
galvo3.jpg
galvo 4.jpg

Either way you will get a gray finish that more or less matches aged galvanizing in terms of shades of gray. But true hot-dip galvo has a mottled look about it. This stuff does not. I have noticed that some other cold galvo compounds seem to have a bit of a shine but ZRC does not.

The directions say you can use spray-painting equipment. In that case you would need to use a thinner.

The paint version when initially applied was noticeably darker than as seen in the photos. It will lighten up as it dries. The aerosol version did not do this. It went on as a light gray as shown and stayed that way.

An very interested to know if this stuff darkens with time. Know of one other cold galvo compound that looks just like old galvo at first but turns to a very dark gray after a while. If any vintage windmiller who has used this stuff and had it turn dark with time please let me know about it. Would probably motivate me to give my antenna tower a finish coat of Rustoleum hammered silver or hammered gray.

ZRC claims that this stuff matches the corrosion inhibiting properties of hot-dip galvanizing and has 95% zinc in the dry film using only Type III "ultra pure" ASTM-D-520 zinc Recognized under the Component Program of Underwriters Laboratories, Inc. as equivalent to hot-dip galvanizing Meets and exceeds Fed. Spec. DOD-P-21035A (Galvanizing Repair Spec); MIL-P-26915A (USAF Zinc Dust Primer); ASTM Des. A-780 (Standard Practice for Repair of Damaged Hot-Dip Galvanized Coatings; SSPC-Paint 20 (Specification for Zinc-Rich Primer) Passes 3,000 hours salt spray testing without failure (ASTM Des. B117) Passes Preece Test (ASTM Des. A239) for hot-dip galvanizing Passes 9-year subtropical testing Low VOC approved in all 50 states ISO 9001 registration assures the highest quality consistently ZRC meets and exceeds SSPC-Paint 20 ( Specification for zinc-rich primers) ZRC meets and exceeds SSPC-Paint 29 ( Specification for zinc dust sacrificial primer, performance-based.)

Sounds impressive, but hopefully some vintage windmiller who knows more than I do about cold galvo products (which isn't much) will let us all know whether to be impressed or not. Would not be overly surprised if he/she says that while all this is good, there are other cold galvo compounds that are just as good. Let those who know speak up.

My recommendation it that when restoring vintage windmill iron, where appearance is important, to apply two coats as a base. If using a brush, use of a thinner would probably help it spread more evenly and smoothly. Several vintage windmillers claim that Rustoleum hammered silver or hammered gray dries to a nice hot-dip galvo look; and might make a good finish coat.

Challenge 27
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Dave Straub
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Joined: Sat Dec 15, 2018 10:49 am
Location: Syracuse Ne
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Re: Putting ZRC to the test

Post by Dave Straub »

I've used Rustoleum with 97% zinc, so thought I would try instead the hammered Rustoleum but found the spray can does not indicate any zinc.
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