Step 1: Recall why iron needs protection.
Iron reacts with moist air, oxygen and water together, to form rust, which weakens and eats away the metal over time.
Step 2: Recall the specific zinc coating method.
Coating iron or steel with a thin layer of zinc creates a barrier that keeps air and water away from the iron underneath, and this specific zinc coating process has its own name, galvanisation.
Step 3: See why zinc still helps even if the coating gets scratched.
Zinc is more reactive than iron, so if the coating is damaged, zinc corrodes first and sacrifices itself, protecting the iron underneath a little longer, this is called sacrificial protection.
Step 4: Rule out the other terms and conclude.
Tinning uses tin, not zinc, and can actually speed up rusting once scratched since tin is less reactive than iron. Anodising is for aluminium, not iron. So coating iron with zinc specifically is called galvanisation. \[ \boxed{\text{Galvanisation}} \]