Some of my customers have asked what kind of paint is best for coating hot-dip galvanized steel. Is there a specific type of paint I should be recommending to my customers?

*Updated 2023

Making paint recommendations can be tricky. First, it could reflect poorly on you or your company if a recommendation turns out problematic. And second, it’s best to leave paint recommendations up to paint suppliers or specialists. Having said that, many types of paint have been applied to hot-dip galvanized steel over the years. Some patterns have emerged with specific types of paint in different environments, with some working better than others.

In the AGA publication, Duplex Systems, you will find a table (Figure 1, below) that discusses the compatibility of 16 types of paint or other barrier coatings that have been applied over hot-dip galvanized steel. While this information should not be looked at as a recommendation, it can be used as a resource to assist in choosing an appropriate type of paint or barrier coating to apply over their hot-dip galvanized steel if the increased corrosion protection offered by a duplex system is desired. Remember though, the specific type of paint or other barrier coating that will be applied over the hot-dip galvanized steel is only part of the formula for ensuring a successful duplex system. The other part of the formula, and probably the most important, is the preparation of the galvanized coating prior to applying the paint. If the preparation of the galvanized coating is inadequate, it does not matter what type of paint is used, it will begin peeling off the galvanized coating sooner rather than later.

Clients asking for recommendations should also be made aware of SSPC Guide 19. Guide 19 addresses both the condition of the galvanizing and the application’s service environment to narrow down types of paint that are compatible under these circumstances. Using Guide 19’s Table 1, you can easily see what paint types are recommended before exploring further options with a paint supplier. For example, for a deteriorated hot-dip galvanized coating in a chemical (<5pH or >10pH) environment, bituminous, coal tar epoxy, and epoxy paint types, would be recommended.

SSPC Guide 19 - Table 1 (Click here for the full SSPC Guide 19)

	Galvanizing Condition			Service Environment
Coating Type	New	Partially Weathered	Deteriorated	Aesthetic	Chemical (pH <5 or >10)	Buried	Marine
Acrylics	Yes	Yes	No	Yes	No	No	Yes
Bituminous	Yes	Yes	Yes	No	Yes	Yes	No
Coal Tar Epoxies	Yes	Yes	Yes	No	Yes	Yes	Yes
Epoxies	Yes	Yes	Yes	--	Yes	Yes	Yes
Inorganic Zinc Rich	No	No	No	No	No	No	No
Latex Acrylics	Yes	Yes	No	Yes	No	No	No
Organic Zinc Rich	No	No	Yes	--	No	No	Yes
Micaceous Iron Oxide Reinforced Polyurethane	Yes	Yes	Yes	No	No	No	Yes
Vinyls	Yes	Yes	Yes	Yes	Yes	No	Yes

Remember, even the best paint systems will fail if the galvanized surface is not properly prepared. So do yourself and your client a favor by emphasizing the importance of surface preparation when discussing paint. The AGA has published an instructional guide, Preparing Hot-Dip Galvanized Steel for Paint. The guide offers a detailed walk-through of the steps necessary to properly prepare a hot-dip galvanized coating for paint or other barrier coating and is available for download in pdf form. It can also be ordered with either CD or DVD with visual demonstrations.

Figure 1: Barrier Coatings Compatibility with HDG Steel

Type	Compatibility	Comments
Acrylics	Sometimes	If the pH of the paint is high, problems may occur due to ammonia reacting with zinc
Aliphatic Polyurethanes	Yes	If used as a top coat for a polyamide epoxy primer, it is considered a superior duplex system
Bituminous	Yes	Used for parts that are to be buried in soil
Chlorinated Rubbers	Yes	High VOC content has severely limited their availability
Coal Tar Epoxies	Sometimes	Rarely used, only if parts are to be buried in soil
Epoxies	Sometimes	If paint is specifically manufactured for use with galvanized steel
Epoxy-Polyamide Cured	Yes	Has superior adherence to galvanized steel
Latex-Acrylics	Yes	Has the added benefit of being environmentally friendly
Latex-Water-based	Sometimes	Consult paint manufacturer
Oil Base	Sometimes	Consult paint manufacturer
Portland Cement in Oil	Yes	Has superior adherence to galvanized steel
Silicones	No	Not for use directly over galvanized steel, can be beneficial in high temperature systems w/ base coat
Vinyls	Yes	Usually requires profiling, high VOC’s have severely limited their availability
Powder Coating	Yes	Low temperature curing powder coatings work exceptionally well over galvanized steel