Water and air有水也有空氣
Iron, oxygen, and water are all there. Gray atoms turn brown and swell, flake away, and the layer underneath starts to rust.
鐵、氧、水都到齊了。灰色的原子變成紅褐色、脹大、剝落，底下那一層也開始鏽。
How Things Work · Unit 5 · Lesson 19 · 萬物原理 單元五 第十九課
Why Does Iron Rust?鐵為什麼會生鏽？
Rust is not dirt. It is iron that has joined with oxygen, with the help of water, and turned into something new. Zoom in on a piece of iron in 3D, take away the water or the air, add salt, and see how paint and zinc keep rust away.
鐵鏽不是髒東西，而是鐵在水的幫忙下和氧結合，變成了另一種新的東西。在 3D 裡放大一塊鐵，把水或空氣拿掉、加一點鹽，再看看油漆和鍍鋅怎麼把鐵鏽擋在外面。
Big idea · 一句話看懂
Rust forms when three things meet: iron, oxygen from the air, and water. Take any one away and iron hardly rusts at all; add salt and it rusts much faster. Rust is loose and flaky, so it falls off and lets fresh iron underneath rust too. That is why we protect iron with paint, oil, or a coat of zinc.
三樣東西碰在一起就會生鏽：鐵、空氣裡的氧、還有水。少了任何一樣，鐵幾乎不會鏽；加了鹽，會鏽得快很多。鐵鏽又鬆又會剝落，一掉下來，底下新的鐵又繼續鏽。所以我們用油漆、油或一層鋅來保護鐵。
3D Model · 3D 模型
Iron Under a Drop of Water 一滴水底下的鐵
Drag to turn the view, and scroll or pinch to zoom. The gray balls are iron atoms, the red pairs are oxygen from the air, and the blue dome is a drop of water. Let the time run, or drag the time slider. Switch off the water or the air, add salt, and try the four surfaces on the right. The checklist shows which of the three things can reach the iron.
拖曳可以旋轉視角，滾輪或雙指可以縮放。灰色的球是鐵原子，紅色成對的小球是空氣裡的氧，藍色的圓頂是一滴水。讓時間自己走，或拉時間滑桿。把水或空氣關掉、加鹽，再試試右邊的四種表面。上面的清單會告訴你，三樣東西裡有哪幾樣碰得到鐵。
A greatly magnified view; the atoms are drawn far bigger and far fewer than real · 放大很多倍的示意圖；原子畫得比真的大非常多、也少非常多
Drag to turn · 拖曳旋轉 Scroll or pinch to zoom · 滾輪／雙指縮放
This 3D model needs WebGL, which this browser does not support. The reading and the cards below still explain everything.
這個瀏覽器不支援 WebGL，無法顯示 3D 模型；下方的課文與卡片一樣能看懂。
- Gray balls: iron atoms
灰色的球：鐵原子 - Brown lumps: rust (iron joined with oxygen)
紅褐色的塊：鐵鏽（鐵和氧結合） - Red pairs: oxygen from the air
紅色成對的小球：空氣裡的氧 - Blue dome: a drop of water
藍色圓頂：一滴水
A teaching model, not a measurement. The “days” and percentages come from a simple formula chosen to show the pattern (no water or no oxygen means no rust, salt makes it faster); how fast real iron rusts depends on the metal, the weather, and much more. Real atoms are far too small to see, and a real piece of iron has more of them than anyone could count. The real chemistry also has several steps that are not shown here.
這是教學用的模型，不是量出來的結果。「天數」和百分比來自一條簡單的算式，只是為了呈現趨勢（沒有水或沒有氧就不會鏽、有鹽鏽得快）；真正的鐵鏽多快，要看金屬、天氣和很多別的條件。真正的原子小到看不見，一塊真的鐵裡的原子多到數不清。真正的化學反應還有好幾個步驟，這裡沒有畫出來。
Model drawn by My Culture Connect as a teaching diagram. What rust is and what it needs follow Wikipedia, “Rust”. · 模型由人師教育協會自繪示意；鐵鏽是什麼、需要什麼條件，依維基百科「Rust」條目。
Reading · 英文閱讀
19
Unit 19: Why Does Iron Rust?
Leave a bicycle outside through a few weeks of rain, and something happens to the chain. Orange-brown spots appear, and the chain feels rough. Leave a pair of wet scissors in a drawer and the same thing happens. We call it rust. But what is rust, and where does it come from?
把腳踏車放在外面淋幾個星期的雨，鏈條就會起變化：出現橘褐色的斑點，摸起來粗粗的。把濕的剪刀收進抽屜，也會發生同樣的事。我們說它生鏽了。可是鐵鏽到底是什麼？它是從哪裡來的？
Rust is not dirt that lands on the metal. It is the metal itself, changed into something new. Iron joins with oxygen from the air, and water helps the change happen. The new stuff is called iron oxide. It is reddish brown, crumbly, and weak. So rust needs three things: iron, oxygen, and water.
鐵鏽不是落在金屬上的髒東西，而是金屬自己變成了另一種新的東西。鐵和空氣裡的氧結合，水在旁邊幫忙讓這個變化發生。這種新的東西叫做氧化鐵，紅褐色、一捏就碎、很脆弱。所以生鏽需要三樣東西：鐵、氧和水。
Take away any one of the three and the rusting almost stops. A dry nail in a dry room stays shiny for a very long time. A nail covered in oil stays shiny too, because the oil keeps water and air away from it. Salt does the opposite: it makes iron rust much faster. That is why bikes, scooters, and railings near the sea rust so quickly.
三樣裡拿掉任何一樣，生鏽幾乎就停下來。乾燥房間裡的乾鐵釘，可以亮很久很久。塗滿油的鐵釘也一樣亮，因為油把水和空氣擋在外面。鹽正好相反：它讓鐵鏽得快很多。所以海邊的腳踏車、機車和欄杆特別容易生鏽。
Rust is especially bad news for iron because it is loose and flaky. It even takes up more room than the iron it came from, so it cracks and falls off. Then fresh iron underneath is open to the air and water, and it rusts too. Given enough time, a whole piece of iron can turn to rust. Aluminum is luckier: it forms a thin, tight skin that protects the metal below.
鐵鏽對鐵特別糟糕，因為它又鬆又會剝落。它佔的空間甚至比原來的鐵還大，所以會裂開、掉下來。這樣一來，底下新的鐵又露在空氣和水裡，也跟著生鏽。只要時間夠久，一整塊鐵都可能變成鐵鏽。鋁就幸運多了：它會形成一層又薄又緊的皮，保護底下的金屬。
So people protect iron by keeping one of the three things away. Paint and oil are walls against water and air. The Eiffel Tower gets about 60 tons of new paint every seven years. Another way is to coat iron with zinc, which keeps protecting it even when it is scratched. And stainless steel has chromium mixed in, which makes an invisible film that shields it.
所以保護鐵的方法，就是把三樣東西裡的一樣擋掉。油漆和油是擋住水和空氣的牆。艾菲爾鐵塔每七年就要重新刷上大約 60 噸的油漆。另一個方法是在鐵的表面鍍一層鋅，就算刮傷了，鋅還是會繼續保護鐵。不鏽鋼則是在鐵裡加了鉻，鉻會形成一層看不見的保護膜。
You can fight rust too. Dry your bike after the rain, and put a drop of oil on the chain. Dry knives, scissors, and iron pans before you put them away. If the paint on something is chipped, tell an adult so it can be touched up. A little care now saves a lot of metal later.
你也可以對抗鐵鏽。下雨之後把腳踏車擦乾，在鏈條上滴一滴油。刀子、剪刀和鐵鍋先擦乾再收起來。看到東西的油漆掉了一塊，就告訴大人，請他們補漆。現在多花一點心思，以後可以保住很多金屬。
Read aloud · 課文朗讀
Questions · 閱讀理解
What three things are needed for rust to form?
Iron, oxygen (from the air), and water.
Why does rust keep eating into iron instead of protecting it?
Because rust is loose and flaky. It falls off, so fresh iron underneath is open to air and water and rusts too.
Name two ways people protect iron from rust.
Any two of these: paint, oil, a coat of zinc (galvanizing), using stainless steel, or simply keeping the iron dry.
Words & Phrases · 生字及片語
rust(n., v.)鐵鏽；生鏽The old gate was covered with rust.那扇舊鐵門上都是鐵鏽。iron(n.)鐵The bridge is made of iron and steel.這座橋是鐵和鋼做的。oxygen(n.)氧；氧氣We breathe in oxygen from the air.我們從空氣裡吸進氧氣。metal(n.)金屬Gold is a soft yellow metal.金是一種柔軟的黃色金屬。flaky(adj.)會一片片剝落的The old paint on the wall was dry and flaky.牆上的舊油漆又乾又會剝落。protect(v.)保護A helmet protects your head.安全帽保護你的頭。coat(n., v.)一層（塗料）；塗上The fence needs a new coat of paint.圍籬需要重新刷一層油漆。scratch(n., v.)刮痕；刮傷There is a long scratch on the car door.車門上有一道長長的刮痕。
Quick Check · 小測驗
1. What is rust?
2. Which of these is NOT needed for rust to form?
3. What does salt do to iron that is wet?
4. Why does rust not protect the iron underneath?
5. How does paint stop rust?
Try It in the Model · 在模型裡試試
Four pieces of iron 四塊鐵
Watch the checklist at the top right: rust only forms while all three boxes are green.
注意右上角的清單：三格都是綠色的時候，才會生鏽。
Salt water鹽水
Add salt to the water and everything speeds up. In this model the iron rusts three times as fast.
在水裡加鹽，一切都變快了。在這個模型裡，鐵鏽得快三倍。
Kept dry保持乾燥
Oxygen is all around, but without water the iron stays gray and shiny. One of the three is missing.
四周都是氧，但是沒有水，鐵還是灰灰亮亮的。三樣東西少了一樣。
Scratched paint油漆刮傷了
Paint keeps water and air out, but rust starts wherever there is a scratch. Then try “Scratched zinc” and compare.
油漆把水和空氣擋在外面，但是哪裡有刮痕，鐵鏽就從哪裡開始。接著試試「鍍鋅刮傷」比較看看。
Rust by the Numbers · 生鏽的數字
The long fight against rust 和鐵鏽的長期抗戰
Keeping a big iron tower standing takes a lot of paint.
要讓一座大鐵塔一直站著，得用掉很多油漆。
3things · 樣東西
Rust needs iron, oxygen, and water. Take one away and it hardly forms.生鏽需要鐵、氧和水，少了一樣就幾乎不會鏽。
7,300tonnes of iron · 公噸的鐵
The metal in the Eiffel Tower, all of which must be kept from rusting.艾菲爾鐵塔的金屬結構有這麼重，每一處都要防鏽。
60tons of paint · 噸油漆
About this much paint goes onto the Eiffel Tower each time it is repainted.艾菲爾鐵塔每重新油漆一次，大約要用掉這麼多油漆。
7years · 年
The Eiffel Tower is repainted about every seven years to keep it from rusting.艾菲爾鐵塔大約每七年重新油漆一次，免得生鏽。
10.5%chromium · 鉻
Stainless steel contains at least this much chromium, which forms a thin film that protects it.不鏽鋼至少含有這麼多的鉻，鉻會形成一層薄薄的保護膜。
Myth vs. Fact · 常見迷思
Four things people get wrong 四個常見的誤會
✗ Myth · 迷思Rust is dirt that sticks to the iron.鐵鏽是黏在鐵上面的髒東西。
✓ Fact · 事實Rust is the iron itself, changed into a new substance. As rust forms, there is less iron left.鐵鏽就是鐵自己，變成了一種新的物質。鐵鏽越多，剩下的鐵就越少。
✗ Myth · 迷思A layer of rust protects the metal underneath.一層鐵鏽可以保護底下的金屬。
✓ Fact · 事實Rust is loose and flaky, so water and air get through and the rusting goes on. Aluminum's thin skin protects it, but rust does not protect iron.鐵鏽又鬆又會剝落，水和空氣照樣進得去，會一直鏽下去。鋁那層薄皮有保護作用，鐵鏽卻保護不了鐵。
✗ Myth · 迷思Iron rusts only when rain falls on it.鐵只有被雨淋到才會生鏽。
✓ Fact · 事實The moisture in damp air is enough. Iron can rust indoors in a humid place without ever getting rained on.潮濕空氣裡的水氣就夠了。在潮濕的地方，鐵放在室內、從來沒淋過雨，也會生鏽。
✗ Myth · 迷思Rust is what gives people tetanus.破傷風是鐵鏽造成的。
✓ Fact · 事實Tetanus comes from bacteria that live in soil and dirt, not from rust. Rusty things are often dirty, so a deep cut from one still needs care.破傷風是住在泥土和髒污裡的細菌造成的，不是鐵鏽。只是生鏽的東西常常很髒，被它刺傷、割傷還是要好好處理。
Remember It · 記憶口訣
Rust in a sentence 一句話記住生鏽
Iron + oxygen + water鐵＋氧＋水
All three together make rust. Take one away to stop it.
三樣到齊就生鏽，拿掉一樣就能擋住它。
Rust is the iron itself鐵鏽就是鐵自己
Not dirt on top, but metal that has changed.
不是上面的髒東西，是變了樣的金屬。
Flaky means no protection會剝落，就保護不了
Rust falls off, and the iron below rusts next.
鐵鏽掉下來，底下的鐵接著鏽。
Salt speeds it up, paint shuts it out鹽讓它變快，油漆把它擋住
Rinse off salt, keep things dry, and fix chipped paint.
把鹽沖掉、保持乾燥、油漆掉了要補。
Safety First · 安全提醒
Before you try anything 動手之前先讀
- Rusty metal can have sharp, rough edges. Do not run your fingers along it.生鏽的金屬邊緣可能又利又粗，不要用手指去摸。
- If a rusty or dirty object cuts you or pokes through your skin, tell an adult right away. The wound must be cleaned, and you may need to see a doctor.被生鏽或髒的東西割傷、刺傷，要馬上告訴大人。傷口要清洗乾淨，也可能需要看醫生。
- Wash your hands with soap after touching rusty things.摸過生鏽的東西之後，要用肥皂洗手。
- Keep steel wool away from flames and from batteries. It can catch fire.鋼絲絨（鋼刷）要遠離火和電池，它會燒起來。
- Do the activities with an adult, label the jars, and never drink anything from them.活動要有大人陪同。瓶子要貼標籤，裡面的東西絕對不可以喝。
Classroom Activity 1 · 課堂活動一
The Rust Race 生鏽大賽
You need · 準備材料
- Four small clear jars or cups, and labels四個透明的小罐子或杯子，和標籤
- Four iron nails or four small pieces of steel wool (not stainless steel)四根鐵釘，或四小團鋼絲絨（不能是不鏽鋼的）
- Water, salt, and a little cooking oil水、鹽、和一點沙拉油
Steps · 步驟
- Jar 1: a dry nail, nothing else. Jar 2: a nail half covered with water.第 1 罐：只放一根乾的鐵釘。第 2 罐：鐵釘泡在水裡，露出一半。
- Jar 3: a nail half covered with salt water. Jar 4: a nail rubbed all over with oil, then half covered with water.第 3 罐：鐵釘泡在鹽水裡，露出一半。第 4 罐：鐵釘整根抹上油，再泡在水裡露出一半。
- Guess the order: which nail will rust first, and which will not rust at all?先猜猜看順序：哪一根最先生鏽？哪一根完全不會鏽？
- Look every day for a week and draw what you see. Where on each nail does the rust begin?連續觀察一個星期，每天把看到的畫下來。每根鐵釘是從哪裡開始鏽的？
Rust often starts right at the water line, where the nail has plenty of both water and air.
鐵鏽常常從水面那一圈開始，因為那裡的水和空氣都很充足。
Classroom Activity 2 · 課堂活動二
Rust Hunt 尋找鐵鏽
You need · 準備材料
- A notebook and a pencil, and an adult to walk with you筆記本和鉛筆，和一位陪你走的大人
Steps · 步驟
- Walk around your school or neighborhood and find five things with rust on them. Look, but do not touch.在學校或住家附近走一圈，找出五樣生鏽的東西。用看的，不要摸。
- For each one, write down where the rust is. Is it at a scratch, a joint, or a place where water sits?每一樣都記下鐵鏽長在哪裡：是刮痕、接縫，還是會積水的地方？
- Now find five metal things with no rust. How is each one protected?再找出五樣沒有生鏽的金屬。它們各是怎麼被保護的？
- Do things near the sea or near a road look different from things that stay indoors?靠海或靠馬路的東西，和一直放在室內的東西，看起來有沒有不一樣？
Paint, a shiny zinc coat, stainless steel, and a roof overhead are all ways to keep one of the three things away.
油漆、亮亮的鍍鋅層、不鏽鋼、頭上有屋頂，都是把三樣東西擋掉一樣的方法。
Sources · 資料出處
Facts and numbers on this page were checked against these sources (October 2026). · 本頁的事實與數字依下列資料查證（2026 年 10 月）。
- Rust is an iron oxide formed by iron and oxygen in the presence of water or air moisture; it is flaky and does not protect the iron underneath, unlike the oxide layers on aluminum鐵鏽是鐵和氧在有水或水氣時形成的氧化鐵；它會剝落、不能保護底下的鐵，不像鋁的氧化層Wikipedia, “Rust” ↗
- Salt (seawater, salt spray) makes iron rust more quickly; rust takes up more volume than the original metal鹽（海水、鹽霧）讓鐵鏽得更快；鐵鏽的體積比原來的金屬大Wikipedia, “Rust” ↗
- Galvanizing coats iron or steel with zinc, which keeps protecting the steel even where the coating is damaged鍍鋅是在鋼鐵表面鍍一層鋅，鍍層受損的地方鋅仍會繼續保護鋼鐵Wikipedia, “Galvanization” ↗
- Stainless steel resists rust because of its chromium content of 10.5% or more, which forms a protective film不鏽鋼因含有 10.5% 以上的鉻、形成保護膜而不易生鏽Wikipedia, “Stainless steel” ↗
- The Eiffel Tower: 7,300 tonnes of metal; 60 tons of paint applied every 7 years to prevent rust艾菲爾鐵塔：金屬結構 7,300 公噸；每 7 年用 60 噸油漆防鏽Wikipedia, “Eiffel Tower” ↗
- Tetanus is caused by Clostridium tetani bacteria found in soil; rust itself does not cause it破傷風由泥土中的破傷風桿菌引起；鐵鏽本身不會造成破傷風Wikipedia, “Tetanus” ↗