Why Can't Epoxy Zinc-rich Primer Be Used As Topcoat? What Are the Matching Combinations?

Epoxy zinc-rich primer is composed of epoxy resin, a large amount of zinc powder, additives and so on. With cathodic protection, corrosion inhibition and shielding triple anti-rust effect, it is the preferred primer for steel structure anti-corrosion and anti-rust in atmospheric environment. Wide range of applications and excellent performance. At this point, many customers will ask, since the performance of epoxy zinc-rich primer is so good, can it be used directly as a topcoat? In fact, this approach is not feasible, and the reasons for it will be explained in detail below. 

1. Epoxy zinc-rich primer is easy to produce zinc salt and paint film chalking

Epoxy resin paints, as we all know, has poor weather resistance. The reason why it is generally used as indoor paint: epoxy resin contains ether bonds, and the resin molecules are easily degraded and broken under the irradiation of solar ultraviolet rays, and the coating film will lose light and chalk. Therefore, epoxy paint is not suitable for use as an outdoor decorative finish.

Epoxy zinc-rich primer belongs to a product in the epoxy resin paint category. Therefore, when used alone as a topcoat, due to the poor weather resistance of the paint film, and the epoxy zinc-rich primer contains a large amount of zinc powder, the zinc powder will interact with oxygen in the air. , water vapor and other reactions will produce zinc salts (commonly known as white rust), which will gradually pulverize and fall off.

2. The protective effect of the topcoat of the epoxy zinc-rich primer is better

Coating is very particular about matching, because the suitable anti-corrosion coating scheme, the longer the protective effect and service life. Coatings are divided into primers, intermediate coatings and topcoats. How to choose the right product matching is very important.

Common supporting schemes for epoxy zinc-rich primers

a. Classic coating scheme for steel structure: epoxy zinc-rich primer + epoxy micaceous iron intermediate paint + acrylic polyurethane paint

b. Bridge anti-corrosion coating scheme: epoxy zinc-rich primer + epoxy micaceous iron intermediate paint + fluorocarbon topcoat/polysiloxane topcoat

c. Coating scheme for steel structure venues: epoxy zinc-rich primer + epoxy micaceous iron intermediate paint + metal fluorocarbon paint

d. Coating scheme for railway bridges: epoxy zinc-rich primer + epoxy micaceous iron intermediate paint + gray aluminum powder graphite alkyd topcoat

After our brief introduction, everyone must have an understanding of why epoxy zinc-rich primers cannot be used as topcoats. If you want to know more about zinc-rich primers, please contact us.