The Difference Between Inorganic Zinc Rich Primer and Epoxy Zinc Rich Primer

With the wide use of zinc rich primers, there are more and more zinc rich primers on the market. There are always many questions about the difference between common epoxy zinc rich primers and inorganic zinc rich primers and which paint is better.

1. Performance of epoxy zinc rich primer and inorganic zinc rich primer

(1) The paint film of epoxy zinc rich primer has good flexibility and adhesion, while inorganic zinc rich primer has excellent high temperature resistance, which can withstand high temperatures of 400℃.

(2) Inorganic zinc rich primer is better than epoxy zinc rich primer in terms of heat resistance, solvent resistance, chemical resistance and static electricity, but the paint film has poor flexibility and construction performance. Inorganic zinc rich primer has some special requirements during construction. For example, its curing depends on high relative humidity, and the mist spraying technology is required for achieving the surface porosity, while the construction requirements of epoxy zinc rich primer are much simpler in comparison. The epoxy zinc rich primer should be mixed with weather-resistant materials.

2. Application of epoxy zinc rich primer and inorganic zinc rich primer

Epoxy zinc rich primer is widely used in the coating of various steel structures in atmospheric environments. For example: inner walls of oil storage tanks, bridges, containers, iron towers, ship hulls, construction steel structures, etc.

In the steel structure anti-corrosion system of the multi-layer coating system, the properties of epoxy zinc rich and inorganic zinc rich are basically the same, and epoxy zinc rich primer can be used to replace the inorganic zinc rich primer. From the perspective of the process and speed of construction, epoxy zinc rich primer is more suitable.

3. The performance of epoxy zinc rich primer and inorganic zinc rich primer in construction

(1) Curing environment: epoxy zinc rich primer has a low relative humidity environment, which has no effect on the curing reaction; inorganic zinc rich primer will not cure under low humidity. Even if it appears to be dry, it needs to be sprinkled with water to accelerate its curing reaction.

(2) Requirements on mixing: The epoxy zinc rich primer is easy to use during construction and does not require continuous mixing; if the mixing of the inorganic zinc rich primer is stopped, the zinc powder will precipitate, especially the water-based inorganic zinc rich primer.

(3) Recoating performance: epoxy zinc rich primer is easy to overcoat without seal paint; the surface of inorganic zinc rich primer is porous, which will cause pinholes and bubbles in the subsequent paint, and special spraying techniques such as mist spraying/system spraying are required .

(4) Recoating interval: 2 to 4 hours for epoxy zinc rich primer at 23℃; inorganic zinc rich primer cures fast, only 0.5 to 1 hour.

(5) Repair performance: The damaged area of epoxy zinc rich primer is easy to repair, and it is designated by the United States Steel Structure Coating Association (SSPC) for the repair of inorganic zinc rich primer; inorganic zinc rich primer is very sensitive to poor surface treatment, and the damaged part is easy to peel off.

(6) Flexibility of paint film: Compared with that of inorganic zinc rich primer, the paint film of epoxy zinc rich primer is less brittle and has good flexibility; the paint film of inorganic zinc rich primer is more brittle and has poor flexibility.

(7) Thickness control: The paint film of epoxy zinc rich primer may have a risk of cracking if the formed film is over 125 microns at a time; the paint film of inorganic zinc rich primer has a risk of cracking if the formed film is over 150 microns at a time.