Name: Zinc-Rich Primer Binder EP-ZR (Epoxy-Based, for ZRP Formulation)
Brand: Coatingsink
SKU: zinc-rich-primer-binder-ep-zr
Availability: InStock

Question 1

What zinc dust loading is required for a zinc-rich primer to provide cathodic protection?

Accepted Answer

To achieve cathodic (galvanic) protection, the dry film must contain sufficient zinc particles in electrical contact with each other and with the steel substrate. This requires a minimum zinc dust content of approximately 80–85% by weight in the dry film (ISO 12944 definition). Below this threshold, the primer provides barrier protection only, not cathodic protection. EP-ZR binder is formulated to accommodate zinc loading up to 85% by weight while maintaining adequate film formation.

Question 2

Should zinc-rich primers be overcoated with an epoxy MIO or vinyl intermediate coat?

Accepted Answer

For optimum long-term corrosion protection in aggressive environments (C4–C5 per ISO 12944), zinc-rich primers should be overcoated with a full system including an intermediate coat (typically epoxy MIO or high-build epoxy) and a topcoat. The intermediate coat seals the porous zinc surface, prevents zinc salts from contaminating subsequent coats (a cause of intercoat adhesion failure), and extends topcoat adhesion life. Direct topcoating over ZRP without an intermediate is only acceptable in mild (C2–C3) environments.

Epoxide Content	suitable for >80% Zn loading
Mixing with Zinc Dust	2:3 to 3:7 ratio (resin:Zn)
Viscosity (25°C, Part A)	500–1500 mPa·s
Dry Film Corrosion Protection	ASTM B117 >500h

Zinc-Rich Primer Binder EP-ZR (Epoxy-Based, for ZRP Formulation)

Specifications

FAQ

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