DENJIRO: Have you ever heard of tinplate and corrugated galvanized iron? I have here a toy, bucket, cans, and a wavy sheet of metal. Can you tell which one is tinplate and which one is corrugated galvanized iron?
BOY: I’m guessing the toy’s made of tinplate? I don’t know about the rest.
DENJIRO: Here’s the answer. The toy and cans are made of tinplate, and the bucket and wavy metal are made of corrugated galvanized iron. So what’s the difference between tinplate and corrugated galvanized iron? You’ll see if you try making them.
They’re both made from the same iron plate. Tinplate is iron plate coated with tin, while coating with zinc makes corrugated galvanized iron. They look similar but have different properties. Let’s try pouring sulfuric acid on both.
BOY: It’s starting to bubble.
DENJIRO: Tin is strong against acid, so nothing happens. Therefore, tinplate is often used on the inside of a food can or tableware. On the other hand, zinc is weak against acid, and the coating melts away. So what sort of properties does zinc have? Let’s perform an experiment with toy boats. They both have metal exposed on the bottom, but one has zinc attached. Let’s see what happens if I place these two boats in saltwater for a day.
NARRATOR: Take a look at what happens. With the boat that doesn’t have zinc, you can see that rust is spreading in the saltwater. Let’s take the boats out and look at them.
DENJIRO: As you can see, the boat with zinc hasn’t rusted. If you attach zinc to metal, the zinc reacts with the saltwater before the metal due to a difference in ionization tendencies. The zinc oxides and protects the metal from rust. This is called sacrificial protection and is used on actual boats as well. Due to this property, corrugated galvanized iron is often used outdoors, for items prone to rust such as buckets and roofs.
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24 июл 2024
