Tips from master painters: Apply epoxy zinc-rich primer on these materials to double the protective effect

2026-01-03 13:36:40

After working in coating production and construction for so many years, I am often asked a very practical question by customers: "Can our material be painted with your epoxy zinc-rich primer?"

This question is on point! Epoxy zinc-rich primer is indeed a "ruthless player" in anti-corrosion, especially in places such as seaside, chemical plants, and bridges that are subject to wind, sun, rain, and corrosive media. It relies on the principle of "cathodic protection" (simply put, it sacrifices the zinc powder on its own body to first "block" corrosion and protect the iron underneath), and has become a star product of industrial anti-corrosion.

But celebrities are not omnipotent. It is like a key designed to open hard locks. It must be matched with the right lock cylinder (base material) to achieve maximum effectiveness. Today, let’s talk in plain English about which materials epoxy zinc-rich primer most “embraces”.

First, its “number one fan”: carbon steel (carbon steel)Most of the steel structures around you, such as the steel beams of factory buildings, the skeleton of cross-sea bridges, and transmission towers, are basically made of carbon steel. It is strong and cheap, but it has a fatal weakness - it is afraid of air, especially humid air. If you are not careful, it will get "red makeup" (rusty) all over your face.

Epoxy zinc-rich primer is a "rust-proof autumn coat" tailor-made for it. After application, the densely packed zinc powder in the paint actively forms a dense protective layer to keep out water vapor and oxygen. At the same time, the zinc powder sacrifices itself to inhibit corrosion and put a long-lasting "protective armor" on the carbon steel. Therefore, as long as it is long-term anti-corrosion of carbon steel structures, epoxy zinc-rich primer is basically the first choice.

The second "iron buddy": cast ironCast iron is the kind of material commonly used for machine bases, pipes, and heavy gears. It is wear-resistant, pressure-resistant, and shock-absorbing, but the surface is usually rough and porous. In humid or acid-base environments, corrosion will also start from these tiny pores.

Applying epoxy zinc-rich primer to cast iron parts can not only effectively seal surface pores and block corrosion paths, but its strong adhesion can also firmly grasp the cast iron surface. Coupled with the cathodic protection of zinc powder, these "iron bumps" can extend their life under harsh working conditions. Remember, though, that cast iron surfaces often have casting residues and must be cleaned before construction.

The most important premise: "A good horse deserves a good saddle" - the surface after sandblastingThis is crucial! Regardless of the carbon steel mentioned above, cast iron, or even some other alloy steel, if you want the epoxy zinc-rich primer to "stick firmly and achieve good results", in most cases, the substrate must be thoroughly sandblasted (or shot blasted)!

Why? Because the adhesion of epoxy zinc-rich primer depends largely on mechanical bite. Sandblasting can remove all rust, scale, old paint, and oil stains on the surface, revealing the true color of the metal and forming a uniform and fine roughness (professionally called "anchor grain").

In this way, when the paint is applied, it is like countless small hooks digging deeply into these rough surfaces, and the adhesion increases dramatically. If the surface is simply polished or even painted with rust, the primer will easily fall off entirely, and even the best cathodic protection will be in vain. Therefore, "thorough sandblasting to Sa2.5 level or above" is a "standard action" that cannot be omitted to exert the effect of epoxy zinc-rich primer.

So, what about other materials?Metals such as stainless steel and aluminum plates that have dense oxide films for corrosion protection generally do not need to use epoxy zinc-rich primer. If used, adverse reactions may occur due to potential differences. There is usually a dedicated matching primer.

As for plastics, concrete, and wood, they are completely in another world, with different material properties, expansion coefficients, and adhesion principles. Epoxy zinc-rich primers simply cannot be used. Please be sure to choose other special primers.

To summarize:Epoxy zinc-rich primer is a "protection expert" who has a special liking for "sandblasted steel surfaces" (especially carbon steel and cast iron). Its core value is to provide long-term cathodic protection for these rust-prone steel materials in harsh environments.