Zinc has a higher negative standard reduction potential ($E^\circ_{\text{Zn}^{2+}/\text{Zn}} = -0.76 \text{ V}$) compared to iron ($E^\circ_{\text{Fe}^{2+}/\text{Fe}} = -0.44 \text{ V}$). This means zinc is more reactive and acts as a stronger reducing agent than iron. Therefore, zinc can be coated on iron to protect it from corrosion (acting as a sacrificial anode in galvanization), but the reverse is not possible because iron cannot reduce zinc ions.