A smuggler could not carry gold by depositing iron on the gold surface since:

Gold has a reduction potential =+1.5 V. Iron has a reduction potential =−0.44 V. Thus, gold has a higher reduction potential than iron. An element with a higher reduction potential is a stronger oxidizing agent. So, gold is a stronger oxidizing agent than iron. Hence, gold will get reduced itself instead of iron. Therefore , a smuggler could not carry gold by depositing iron on the gold surface.