Zinc powder plays several important roles in coatings, primarily in corrosion protection and performance enhancement:
1. Cathodic Protection
Zinc has a more negative electrochemical potential than metals like steel. In an electrolytic environment, zinc atoms easily lose electrons and become the anode, while steel acts as the cathode. As the zinc corrodes (sacrificial anode), electrons flow to the steel surface, preventing its oxidation and effectively protecting the steel substrate from corrosion.
2. Enhanced Barrier Effect
Zinc powder acts as a physical filler within the coating layer, forming a barrier that blocks corrosive agents such as oxygen and water vapor from reaching the metal substrate. Flake-shaped zinc powder is especially effective due to its high diameter-to-thickness ratio. It forms overlapping layers that increase diffusion paths, reduce thermal expansion mismatch between the coating and metal substrate, minimize shrinkage during curing, and relieve internal stresses in the coating. This helps prevent cracking, peeling, and improves adhesion and impermeability.
3. Self-Healing Ability of the Coating
When the coating is mechanically damaged and the base metal is exposed, zinc in the nearby area acts as a sacrificial anode. The corrosion current flows to the exposed steel, and zinc corrosion products precipitate at the damaged site, forming a protective layer. This slows down further corrosion and imparts a self-healing function to the coating.
4. Improved Coating Performance
Zinc powder enhances the physical properties of coatings, including hardness and abrasion resistance. It also improves adhesion, enabling better bonding of the coating to the metal surface, which boosts the overall performance and durability of the protective film.
5. Passivation of the Steel Substrate
During the drying and film-forming process, changes in pH levels may reduce the effectiveness of electrochemical protection. At this stage, zinc powder in the coating plays a key role in passivating the steel surface, providing additional corrosion resistance.
Post time: Jun-06-2025
