What is the difference between barrier protection and galvanic protection for steel?

The primary difference between barrier protection and galvanic protection lies in how they prevent the corrosion of steel.

Barrier Protection

Barrier protection functions by physically isolating the metal from its environment. By applying an impermeable layer—such as paint, enamel, or certain metallic coatings—the surface is shielded from moisture and oxygen, which are necessary for the electrochemical reactions that cause rust. If this barrier is breached, however, the underlying steel becomes vulnerable to corrosion.123

Galvanic Protection

Galvanic protection, a form of cathodic protection, relies on electrochemical activity rather than just physical separation. It utilizes a more electronegative (active) metal, such as zinc, in contact with the steel.32

If the coating is scratched or damaged, the zinc acts as a sacrificial anode. Because it is more active than iron, the zinc corrodes preferentially, effectively "sacrificing" itself to protect the exposed steel from rusting. Galvanization is a common process that provides both methods simultaneously: it creates a physical barrier while ensuring that galvanic protection remains active if that barrier is compromised.43