June 8, 2023
If you have ever wondered what sets our paint apart from the regular paint you could find at a home improvement store, the answer is that our “paint” is not a paint at all. What is the difference? ZRC Cold Galvanizing Compound is zinc rich!
The zinc dust in a cold galvanizing compound is used to provide corrosion protection. This zinc is what makes the paint electrically conductive. It is the crucial ingredient for the product you turn to for galvanizing steel. This is because the zinc sacrificially corrodes instead of the steel, thereby protecting the substrate.
Zinc rich coatings don't corrode in the same fashion as other metals do. For this reason, zinc dust is used in paints to avoid corrosion and rusting of the material that it's applied to protect. That’s not to say all zinc is the same. If you use inferior zinc dust, you risk impeding true cathodic protection on your steel for years to come. You can learn more about this in our blog, Zinc In Action: How Zinc-Rich Compounds Prevent Corrosion.
What Is Zinc Rich Coating?
Before we go any further, let’s be clear on exactly what is meant by “zinc rich coating.” A zinc rich coating is a coating that contains a high percentage of zinc dust which sacrificially corrodes when in direct contact with steel. Zinc rich coatings are applied to protect steel surfaces from corrosion and extend the surface's life. They provide cathodic protection to metals similar to the hot-dipped galvanizing process.
Zinc-rich paint can prevent steel surfaces from rusting and corroding. It has many industrial applications. The paint can provide a heavy-duty coating for large-scale structures such as bridges, fences and gates, infrastructure, transmission towers, marine equipment, and green power projects like solar and wind towers.
Why Does the Quality of Zinc Dust Matter?
There are three factors that affect the quality of the zinc rich cold galvanizing compound. Perhaps the most important is the quality of the dust itself, meaning the purity of zinc dust being used. You see, zinc dust is mined out of the earth; it is a natural product. There is simply no way of mining it without some amount of impurities being scooped up right along with the raw state. Zinc dust has a lot of impurities, so the producers refine it and take these impurities out.
It perhaps goes without saying that not all companies take out the same level of impurities. This is why the ASTM D520 regulates the Standard Specification for Zinc Dust Pigment. There are three levels: Type I, Type II, and Type III – each pertaining to the purity of the zinc dust of the product.
Type I is not very pure. This compound has a greater amount of lead, chlorine, cadmium, sulfur, and plenty of other nasty stuff. If you settle for Type I, you may be buying zinc dust but you are only getting 94% pure zinc. The other 6% is little more than filler that gives poor corrosion resistance, toxic garbage in fact.
Type III, at the far opposite end of the spectrum, requires the zinc to be extremely clean and pure. It is about 97% pure, which makes a big difference in the quality of coating and how much protection it gives.
The Hidden Dangers of Using Type 1 Zinc Dust
Did you catch in the section above that Type I zinc dust has lead in it? Yes, the same lead that has been proven to have such dangerous side effects we know longer paint our homes with products that contain it. Lead is dangerous! Old bridges and structural steel built in decades past used this poor-quality zinc dust and are now suffering the consequences. If you sandblast a zinc rich coating off of a surface that is Type I or Type II, it has so much lead that it requires a lead abatement project. This is extremely costly. When these structures come up for repair, the owners must sandblast it off, have their crew wear masks and full hazmat suits so as to not get exposed to the high levels of lead, and dispose of it as hazardous waste.
Toxicity issues are not something to brush aside. Type III zinc dust has been proven not to be hazardous. You can sandblast it off and paint again when the time comes for your steel structure to get a fresh layer of protection. You may wonder why anyone would not choose this option, and it's because stripping out impurities is expensive. While it is more costly for us to buy the zinc dust in Type 3, it is worth it. We always buy and use the highest-quality zinc dust in our cold galvanizing compounds and that’s what makes us unique. All of our products are made with this, never Type I or Type II – ever!
Other Factors That Affect the Quality of Zinc Rich Paint
The quality of the zinc dust isn’t the only factor in how the compound turns out. As well, the quantity of the zinc dust matters. There is a lot of zinc in ZRC products! There is 95% zinc in the dried film of ZRC cold galvanizing compounds, meaning 95% of the applied paint is zinc. The remaining material is resin that binds the zinc particles together. Many of our competitors have a zinc content of 70% or lower, meaning their zinc-rich paint isn’t really that rich at all.
The last factor that affects that quality of your zinc-rich paint is the binding system that holds it together. It must be specifically formulated in order to not encapsulate the zinc. Without going too deep into the chemistry behind the product, know that in order for the product to provide true cathodic protection, nothing can be in between the zinc. Our binder holds it all together without encapsulating the zinc. This is because the zinc needs to pass an electrical charge and can’t without touching one another.
How Long Does Zinc Rich Coating Last?
All things considered, the length of life expectancy for any zinc dust depends on the environment it is in. A steel structure in a chemical plant is going to be corrosion-proof for a relatively short amount of time because of corrosion materials in the air, like chlorine and acids. If you’re out in the dry desert, the zinc will last much longer. Everything from how close the structure is to salt water, to the humidity of the air, and beyond all affects the life expectancy of a zinc product.
Yet, not all zinc products will last as long as others – even in the same environment. The level of electrical conductivity in Type I zinc dust is much less than ours. You can expect ZRC products to last longer and have to be redone a lot less than Type I.
You want to use a product that only uses Type III zinc dust. Otherwise, you’re looking at a future of redoing the project sooner than would otherwise be needed, a lead abatement project that is going to cost you a lot of money, and exposing your workers to toxic health hazards. Clearly, the quality of zinc dust is critical to your long-term satisfaction. That’s why it just makes sense to choose ZRC the first time!
