What is the main function of a zinc-rich primer in coating systems?

• A. It forms a permanent barrier that cannot be penetrated
• B. It is a decorative finish
• C. It reduces the need for maintenance
• D. It provides sacrificial galvanic protection to steel, delaying corrosion if the topcoat is damaged

Answer: (D)

Zinc-rich primers are designed to provide sacrificial galvanic protection for steel. The high zinc content makes the coating act as an anode relative to the steel substrate. If the topcoat is damaged and moisture reaches the primer, the zinc will corrode first, sacrificing itself to protect the steel from rusting. This delays corrosion and extends the life of the coating system even when the outer layer is breached. While a good zinc-rich primer can still offer some barrier properties, its defining function is this sacrificial protection, rather than decoration or simply reducing maintenance.