I have a galvanized tank that someone painted. I stripped off all of the paint which also took off some of the galvanizing. I sprayed it with ZRC Galvilite. I'd like to put a protective clear-coat over the Galvilite. Regarding topcoating, ZRC says:
TOPCOATING: After 24-48 hours, ZRC may be topcoated with acrylic, chlorinated rubber, epoxy, urethane or vinyl type products. DO NOT TOPCOAT WITH ALKYD, ALKYD-MODIFIED ACRYLIC, OR LACQUER TYPE PRODUCTS.
Do you have any suggestions for a good clear coat to go over the Galivilite?
If you used a cold galvanizing spray then that is the topcoat. You should not have to put anything further over it. The zinc dust in the binding film is the sacrificial metal that corrodes instead of the steel. That’s how it’s designed.
If you use an epoxy primer /topcoat system instead of a sacrificial zinc system, the idea is that the epoxy provides a waterproof and therefore oxygen transfer proof coating that will lock in any rust and also prevent any oxygen from transferring through to initiate corrosion. Therefore the surface of the steel is held in limbo that can’t continue to rust or start new rust, unless the coating is breached. With the zinc system, if the coating is breached then corrosion will only be present where the actual steel is exposed and no further. With the epoxy primer system if the surface is breached the corrosion could technically crawl under the coating because it will not sacrifice itself as a less noble metal. However, since epoxy grips to steel so well and forms an incredible bond this phenomenon is somewhat minimized.
Powdercoating is tough on the surface but rust can develop underneath and form corrosion bubbles that are sometimes hard to detect because the Powdercoating film is thick and can hide underlying problems. The rust can creep and it can get really bad, especially on aluminum. I think Powdercoating on items that are going to be immersed in salt water is a really bad idea.
Epoxy has a very fine molecule structure that will not allow water to pass through plus it’s long chain structure is also very strong and forms “legs” or tentacles that grip into every nook and cranny of the steel at a microscopic level.
The old Etch primers are a thing of the past as the acid converters have been discontinued and the one part new stuff is basically crap and doesn’t really etch into anything.
Epoxy is far superior in every aspect as a DTM primer (direct to metal) if you want a shiny topcoat color choice.
The topcoat is simply a color coat for gloss, durability, and long term UV resistance. Epoxy barrier coats / primers need to be top coated to be UV resistant and completed as a system. Epoxies by themselves are not UV resistant.
Clear coating over a zinc coating would be kind of awkward at best and I couldn’t guarantee the long term results. If you want a shiny grey finish then use shiny grey paint over the proper primer.
There’s nothing wrong with zinc coating, it works great and I don’t mind the dull variegated grey industrial look.
Cold galvanizing steel and leaving it is a totally legit system. I have a chunk of steel I sprayed cold galvanizing zinc on as a test and put it on my fence. It’s still holding up great going on 3 years now outdoors in the open sun and rain.
