PROJ-CH-0047: Redox Reactions — Corrosion Project 氧化还原反应：腐蚀项目 完整解答¶
状态: ✅ 已完成
创建日期: 2026-02-18
最后更新: 2026-02-18
Experiment Data Table 实验数据表¶
| # | Contents 内容 | First Obs. 第一次观察 | Second Obs. 第二次观察 | Corrosion 腐蚀程度 |
|---|---|---|---|---|
| 1 | Filled with Water (Control) 水（对照） | Some Rust 少量锈 | More Rust 更多锈 | 5 |
| 2 | Half Water, Half Air 半水半空气 | Some Rust | More Rust | 7 |
| 3 | 0.05 M NaCl (Table Salt) 食盐 | Some Rust | More Rust | 8 |
| 4 | 0.05 M HCl 盐酸 | Yellow Solution 黄色溶液 | Yellow Solution | 10 |
| 5 | 0.05 M NaOH 氢氧化钠 | No Change 无变化 | No Change | 1 |
| 6 | Air only 仅空气 | No Change | No Change | 1 |
| 7 | Boiled Water (air removed) 煮沸水 | No Change | Tiny amount of rust 微量锈 | 3 |
| 8 | Zinc wrapped + water 锌包裹+水 | No Change | Tiny amount of rust | 3 |
| 9 | Magnesium wrapped + water 镁包裹+水 | No Change | Tiny amount of rust | 2 |
| 10 | Copper wrapped + water 铜包裹+水 | Some Rust | More Rust | 8 |
| 11 | Grease coated + water 涂油脂+水 | No Change | No Change | 1 |
| 12 | Galvanized nail + water 镀锌钉+水 | No Change | No Change | 1 |
Research Questions 研究问题¶
Research Q1¶
EN (Original): Iron is the fourth most abundant element by mass in the earth's crust after oxygen, silicon and aluminum. Iron is the second most abundant metal after aluminum. However, it is more widely used than aluminum. Find a reason why this is the case.
中文翻译： 铁是地壳中按质量计第四丰富的元素（仅次于氧、硅、铝），是第二丰富的金属（仅次于铝），但却比铝使用更广泛。找出原因。
Answer 答案:
EN: Iron is more widely used than aluminum because it is much cheaper and easier to extract. Iron ore (hematite, Fe₂O₃) can be reduced using coke (carbon) in a blast furnace at relatively moderate temperatures. Aluminum extraction, by contrast, requires the Hall-Héroult electrolysis process, which consumes enormous amounts of electrical energy (aluminum oxide has a very high melting point of ~2072°C). Historically, iron smelting technology has been available for thousands of years, while aluminum mass production only became feasible in the late 1800s. Additionally, iron/steel has superior mechanical properties (higher strength, hardness) for structural applications.
中文： 铁比铝使用更广泛，因为铁更便宜、更容易提取。铁矿石（赤铁矿 Fe₂O₃）可用焦炭在高炉中还原。而铝的提取需要霍尔-埃鲁电解法，消耗大量电能。此外，铁/钢的机械性能更优（强度高、硬度大），适合结构应用。
Research Q2¶
EN (Original): Most iron is converted into steel before use. Which other element is most commonly alloyed with iron to create steel?
中文翻译： 大多数铁在使用前被转化为钢。哪种元素最常与铁合金形成钢？
Answer 答案:
EN: Carbon (C). Steel is an alloy of iron with a small percentage of carbon (typically 0.2%–2.1% by weight). The carbon atoms occupy interstitial positions in the iron lattice, preventing the iron atoms from sliding past each other, which increases hardness and tensile strength.
中文： 碳（C）。钢是铁与少量碳（通常按重量0.2%–2.1%）的合金。碳原子占据铁晶格的间隙位置，阻止铁原子滑动，从而增加硬度和抗拉强度。
Research Q3¶
EN (Original): What is the biggest drawback of using iron over aluminum? Hint: check the title of this project!
中文翻译： 使用铁而非铝的最大缺点是什么？提示：看项目标题！
Answer 答案:
EN: Corrosion (rusting). Iron readily reacts with oxygen and water to form iron oxide (rust, Fe₂O₃·xH₂O), which is porous and flaky — it does NOT protect the underlying metal, so corrosion continues until the metal is consumed. Aluminum, by contrast, forms a thin, dense, adherent layer of aluminum oxide (Al₂O₃) that passivates the surface and prevents further corrosion.
中文： 腐蚀（生锈）。铁容易与氧气和水反应形成氧化铁（铁锈），铁锈疏松多孔，不能保护下层金属，腐蚀持续进行。而铝形成致密的氧化铝保护膜，阻止进一步腐蚀。
Research Q4¶
EN (Original): What are the two common oxidation numbers of iron?
中文翻译： 铁的两个常见氧化数是什么？
Answer 答案:
EN: +2 (ferrous / iron(II), Fe²⁺) and +3 (ferric / iron(III), Fe³⁺).
中文： +2（亚铁/铁(II)，Fe²⁺）和 +3（铁/铁(III)，Fe³⁺）。
Research Q5¶
EN (Original): What does it mean to "galvanize" iron?
中文翻译： "镀锌"铁是什么意思？
Answer 答案:
EN: To galvanize iron means to coat it with a layer of zinc (Zn). This is typically done by dipping the iron into molten zinc (hot-dip galvanizing). The zinc coating protects iron in two ways:
- Barrier protection — the zinc layer physically separates iron from oxygen and water
- Sacrificial protection — even if the coating is scratched, zinc (E° = −0.76 V) is more reactive than iron (E° = −0.45 V), so zinc oxidizes preferentially, protecting the iron cathodically
中文： 镀锌是在铁表面涂一层锌（通常通过热浸镀锌）。锌的保护机制有两层：(1) 物理隔离——锌层将铁与氧气和水隔开；(2) 牺牲保护——锌（E° = −0.76 V）比铁（E° = −0.45 V）更活泼，即使涂层刮破，锌会优先氧化，保护铁。
Research Q6¶
EN (Original): What is the common name for the substance formed when iron corrodes? Hint: you see it on old cars.
中文翻译： 铁腐蚀时形成的物质的俗名是什么？提示：在旧车上能看到。
Answer 答案:
EN: Rust (铁锈). Chemically, rust is hydrated iron(III) oxide: Fe₂O₃·xH₂O. It appears as a reddish-brown flaky coating on iron surfaces.
中文： 铁锈（Rust）。化学成分为水合氧化铁(III)：Fe₂O₃·xH₂O，呈红棕色片状。
Analysis Questions 分析问题¶
Analysis Q1¶
EN (Original): When you compare test tube 6 to test tube 1 it should be obvious that water is necessary for corrosion. Compare test tube 7 to test tube 1, what else is required for corrosion?
中文翻译： 比较试管6和试管1可知水是腐蚀的必要条件。比较试管7和试管1，腐蚀还需要什么？
Answer 答案:
EN:
- Test tube 1 (water, exposed to air): Corrosion = 5
- Test tube 7 (boiled water — dissolved oxygen removed): Corrosion = 3
Boiled water has had most dissolved air (oxygen) removed. The significantly lower corrosion in tube 7 compared to tube 1 shows that oxygen (dissolved air) is also required for corrosion. Iron needs both water AND oxygen to corrode effectively.
中文：
试管1（水+空气）：腐蚀 = 5；试管7（煮沸水，溶解氧被去除）：腐蚀 = 3。煮沸水去除了溶解的空气（氧气），试管7腐蚀明显低于试管1，说明氧气也是腐蚀所必需的。铁腐蚀同时需要水和氧气。
Analysis Q2¶
EN (Original): Specifically, what component of your answer above is required for corrosion?
中文翻译： 具体来说，上述答案中哪个成分是腐蚀所必需的？
Answer 答案:
EN: Oxygen (O₂). Specifically, it is the dissolved oxygen in water (or atmospheric oxygen in contact with wet iron) that acts as the oxidizing agent in the corrosion process.
中文： 氧气（O₂）。具体来说，是水中的溶解氧（或与湿铁接触的大气中的氧气）作为腐蚀过程的氧化剂。
Analysis Q3¶
EN (Original): Look at the results from test tubes 1, 3, 4 and 5 and rank salt, base, acid and water in terms of how much they increase corrosion.
中文翻译： 查看试管1、3、4和5的结果，按增加腐蚀的程度排列盐、碱、酸和水。
Answer 答案:
EN:
| Test Tube | Solution | Corrosion |
|---|---|---|
| 4 | 0.05 M HCl (Acid) | 10 |
| 3 | 0.05 M NaCl (Salt) | 8 |
| 1 | Water | 5 |
| 5 | 0.05 M NaOH (Base) | 1 |
Ranking (most to least corrosion):
$$\boxed{\text{Acid} > \text{Salt} > \text{Water} > \text{Base}}$$
- Acid accelerates corrosion most because H⁺ ions provide additional oxidizing agent and increase the reduction potential
- Salt increases corrosion by acting as an electrolyte, improving ion conductivity
- Water alone causes moderate corrosion
- Base actually inhibits corrosion — OH⁻ ions form a passive iron hydroxide layer that protects the surface
中文：
排序（腐蚀从多到少）：酸 > 盐 > 水 > 碱
- 酸腐蚀最强：H⁺ 提供额外的氧化剂，增加还原电位
- 盐增加腐蚀：作为电解质，提高离子导电性
- 水单独引起中等腐蚀
- 碱实际上抑制腐蚀：OH⁻ 在表面形成钝化层
Analysis Q4¶
EN (Original): The corrosion of iron is a multi-step process. The first step is to oxidize iron into iron(II) ions. Look this up on the Standard Reduction Potentials of Half Cells chart in your data booklet and record the reaction and the E° value below. As this is an oxidation reaction you must reverse the sign on the E° value.
中文翻译： 铁的腐蚀是多步过程。第一步是将铁氧化为铁(II)离子。查标准还原电位表，记录反应和 E° 值。因为这是氧化反应，需反转 E° 符号。
Answer 答案:
EN:
From the Standard Reduction Potentials table:
$$\text{Fe}^{2+}(aq) + 2e^- \rightarrow \text{Fe}(s) \quad E° = -0.45\;\text{V}$$
Reversed for oxidation:
$$\boxed{\text{Fe}(s) \rightarrow \text{Fe}^{2+}(aq) + 2e^- \quad E°_{\text{ox}} = +0.45\;\text{V}}$$
中文：
标准还原电位表：Fe²⁺ + 2e⁻ → Fe，E° = −0.45 V
反转为氧化：Fe → Fe²⁺ + 2e⁻，E°_ox = +0.45 V
Analysis Q5¶
EN (Original): A redox reaction always requires both oxidation and reduction. This means we need an oxidizing agent. In this case, that agent is the answer to question 2. There are two equations for the reduction of this element from the Standard Reduction Potentials of Half Cells. One in neutral water (10⁻⁷ M), one in 1 M acid. Write these reactions below with their E° values.
中文翻译： 氧化还原反应需要氧化和还原两部分。氧化剂是第2题的答案（氧气）。标准还原电位表中有两个氧的还原方程式——一个在中性水中，一个在1M酸中。写出这些反应及 E° 值。
Answer 答案:
EN:
In neutral water (10⁻⁷ M H⁺):
$$\frac{1}{2}\text{O}_2(g) + 2\text{H}^+(10^{-7}\text{M}) + 2e^- \rightarrow \text{H}_2\text{O}(l) \quad E° = +0.82\;\text{V}$$
In 1 M acid:
$$\frac{1}{2}\text{O}_2(g) + 2\text{H}^+(1\text{M}) + 2e^- \rightarrow \text{H}_2\text{O}(l) \quad E° = +1.23\;\text{V}$$
中文：
中性水（10⁻⁷ M H⁺）：½O₂ + 2H⁺(10⁻⁷) + 2e⁻ → H₂O，E° = +0.82 V
1M 酸：½O₂ + 2H⁺(1M) + 2e⁻ → H₂O，E° = +1.23 V
Analysis Q6¶
EN (Original): Which of the above reactions will proceed more quickly, in acidic solution or neutral water? Explain. Does this agree with the results from the experiment (test tubes 1 and 4)?
中文翻译： 上述哪个反应更快——在酸性溶液中还是中性水中？解释。是否与实验结果（试管1和4）一致？
Answer 答案:
EN:
The reaction proceeds more quickly in acidic solution because:
-
Higher E° value — In acid, E° = +1.23 V vs neutral water E° = +0.82 V. Combined with iron oxidation (+0.45 V):
- In acid: E°_net = +1.23 + 0.45 = +1.68 V
- In neutral water: E°_net = +0.82 + 0.45 = +1.27 V
Higher net E° means a larger thermodynamic driving force.
-
Higher H⁺ concentration — More H⁺ ions increase the rate of the reduction half-reaction.
Experimental agreement: Yes! Test tube 4 (0.05 M HCl, acid) had corrosion = 10, while test tube 1 (water) had corrosion = 5. This confirms that acid accelerates corrosion, consistent with the higher E° and H⁺ concentration.
中文：
酸性溶液中反应更快，因为：(1) E° 更高——酸中净 E° = +1.68 V vs 中性水净 E° = +1.27 V，驱动力更大；(2) H⁺ 浓度更高，加速还原半反应。
与实验一致： 试管4（酸）腐蚀 = 10，试管1（水）腐蚀 = 5。✓
Analysis Q7¶
EN (Original): Iron(II) ions can be further oxidized to form iron(III) ions. Write this oxidation reaction with its E° value below.
中文翻译： 铁(II)离子可以进一步被氧化为铁(III)离子。写出这个氧化反应及其 E° 值。
Answer 答案:
EN:
From the Standard Reduction Potentials table:
$$\text{Fe}^{3+}(aq) + e^- \rightarrow \text{Fe}^{2+}(aq) \quad E° = +0.77\;\text{V}$$
Reversed for oxidation:
$$\boxed{\text{Fe}^{2+}(aq) \rightarrow \text{Fe}^{3+}(aq) + e^- \quad E°_{\text{ox}} = -0.77\;\text{V}}$$
This oxidation is driven by the presence of oxygen, which acts as the oxidizing agent (as in Q5).
中文：
标准还原电位：Fe³⁺ + e⁻ → Fe²⁺，E° = +0.77 V
反转为氧化：Fe²⁺ → Fe³⁺ + e⁻，E°_ox = −0.77 V
此氧化由氧气驱动（氧气作为氧化剂）。
Analysis Q8¶
EN (Original): The reduction reaction in this experiment uses up H⁺ ions. This produces OH⁻ ions in solution. What you see as rust is a precipitate that forms between iron(III) ions and hydroxide ions. Write this reaction below.
中文翻译： 实验中的还原反应消耗 H⁺ 离子，产生 OH⁻ 离子。你看到的铁锈是铁(III)离子和氢氧根离子之间形成的沉淀。写出反应。
Answer 答案:
EN:
$$\boxed{\text{Fe}^{3+}(aq) + 3\text{OH}^-(aq) \rightarrow \text{Fe(OH)}_3(s)}$$
Iron(III) hydroxide is an insoluble reddish-brown precipitate. Over time, it dehydrates to form rust (Fe₂O₃·xH₂O).
The overall corrosion process can be summarized:
- Fe → Fe²⁺ + 2e⁻ (oxidation)
- ½O₂ + 2H⁺ + 2e⁻ → H₂O (reduction, consumes H⁺, effectively producing OH⁻)
- Fe²⁺ → Fe³⁺ + e⁻ (further oxidation by O₂)
- Fe³⁺ + 3OH⁻ → Fe(OH)₃ (precipitation → rust)
中文：
$$\text{Fe}^{3+}(aq) + 3\text{OH}^-(aq) \rightarrow \text{Fe(OH)}_3(s)$$
氢氧化铁(III) 是不溶性红棕色沉淀，随时间脱水形成铁锈（Fe₂O₃·xH₂O）。
腐蚀全过程：(1) Fe 氧化为 Fe²⁺；(2) O₂ 还原消耗 H⁺，产生 OH⁻；(3) Fe²⁺ 进一步氧化为 Fe³⁺；(4) Fe³⁺ + 3OH⁻ → Fe(OH)₃ 沉淀（铁锈）。
Analysis Q9¶
EN (Original): Compare the results for test tubes 8, 9 and 10. Which metal(s) slowed corrosion and which metal(s) hastened corrosion?
中文翻译： 比较试管8、9和10的结果。哪些金属减缓了腐蚀？哪些加速了腐蚀？
Answer 答案:
EN:
| Test Tube | Metal Wrapped | Corrosion | vs Control (tube 1 = 5) |
|---|---|---|---|
| 8 | Zinc | 3 | Slowed ↓ |
| 9 | Magnesium | 2 | Slowed ↓ |
| 10 | Copper | 8 | Hastened ↑ |
- Slowed corrosion: Zinc (3) and Magnesium (2) — both reduced corrosion below the water control
- Hastened corrosion: Copper (8) — increased corrosion above the water control
中文：
- 减缓腐蚀：锌（3）和镁（2）——腐蚀低于水对照组
- 加速腐蚀：铜（8）——腐蚀高于水对照组
Analysis Q10¶
EN (Original): Explain the above results using the Standard Reduction Potentials of Half Cells table in your data booklet.
中文翻译： 用标准还原电位表解释上述结果。
Answer 答案:
EN:
The key is comparing E° values:
| Metal | Half-Reaction | E° (V) |
|---|---|---|
| Mg | Mg²⁺ + 2e⁻ → Mg | −2.37 |
| Zn | Zn²⁺ + 2e⁻ → Zn | −0.76 |
| Fe | Fe²⁺ + 2e⁻ → Fe | −0.45 |
| Cu | Cu²⁺ + 2e⁻ → Cu | +0.34 |
Zinc and Magnesium (more negative E° than Fe):
Both Zn (−0.76) and Mg (−2.37) have more negative E° values than Fe (−0.45). This means they are more easily oxidized than iron. When in contact with iron, they act as sacrificial anodes — they oxidize preferentially instead of iron. The iron becomes the cathode (protected). This is cathodic protection.
- Mg is even more effective (corrosion = 2) than Zn (corrosion = 3) because its E° is much more negative.
Copper (more positive E° than Fe):
Cu (+0.34) has a more positive E° than Fe (−0.45). Copper is less easily oxidized than iron. When copper is in contact with iron, iron becomes the anode (oxidized) and copper becomes the cathode. The copper actually accelerates iron's corrosion by creating a galvanic cell where iron preferentially loses electrons. This is why corrosion increased to 8.
中文：
关键是比较 E° 值。Zn（−0.76）和 Mg（−2.37）的 E° 比 Fe（−0.45）更负，更容易被氧化，作为牺牲阳极优先氧化，保护铁（阴极保护）。Mg 效果更好因为 E° 更负。
Cu（+0.34）的 E° 比 Fe 更正，不容易被氧化。铜与铁接触时，铁成为阳极被优先氧化，铜作为阴极加速了铁的腐蚀。
Analysis Q11¶
EN (Original): Explain the results of test tube 11.
中文翻译： 解释试管11的结果。
Answer 答案:
EN:
Test tube 11 (grease-coated nail, corrosion = 1) showed almost no corrosion. The grease coating acts as a physical barrier that prevents both water and oxygen from reaching the iron surface. Since corrosion requires both H₂O and O₂ in contact with the metal (as established in Q1–Q2), blocking this contact stops the corrosion process entirely.
This is an example of barrier protection — no electrochemistry is involved, just physical isolation from the corrosive environment.
中文：
试管11（涂油脂钉，腐蚀 = 1）几乎无腐蚀。油脂涂层作为物理屏障，阻止水和氧气接触铁表面。由于腐蚀同时需要 H₂O 和 O₂，阻断接触即可阻止腐蚀。这是屏障保护的例子，不涉及电化学，仅靠物理隔离。
Analysis Q12¶
EN (Original): Explain the results of test tube 12.
中文翻译： 解释试管12的结果。
Answer 答案:
EN:
Test tube 12 (galvanized nail, corrosion = 1) showed almost no corrosion. A galvanized nail is coated with a layer of zinc, which provides dual protection:
- Barrier protection — the zinc coating physically blocks water and oxygen from the iron surface (same mechanism as grease in Q11)
- Sacrificial/cathodic protection — even if the zinc coating is scratched or damaged, zinc (E° = −0.76 V) is more reactive than iron (E° = −0.45 V), so it oxidizes preferentially, protecting the iron electrochemically
In this experiment, the intact zinc coating likely provided mainly barrier protection, resulting in corrosion = 1 (same as grease).
中文：
试管12（镀锌钉，腐蚀 = 1）几乎无腐蚀。镀锌提供双重保护：
- 屏障保护——锌涂层物理阻隔水和氧气
- 牺牲/阴极保护——即使涂层破损，锌（E° = −0.76 V）比铁（E° = −0.45 V）更活泼，优先被氧化，电化学保护铁
本实验中完整的锌涂层主要提供屏障保护，腐蚀 = 1。
Further Investigation Questions 深入研究问题¶
Further Q1¶
EN (Original): Blocks of magnesium are connected at intervals to hulls of ships to prevent the corrosion of iron. They are called "sacrificial anodes" since they sacrifice themselves to prevent the iron from corroding but this means they need to be replaced periodically. Why does it make economic sense to replace the blocks of magnesium?
中文翻译： 镁块被间隔连接在船体上以防止铁的腐蚀，称为"牺牲阳极"。为什么定期更换镁块在经济上是合理的？
Answer 答案:
EN:
It makes economic sense because:
- Magnesium is far cheaper than repairing or replacing a steel ship hull. A ship hull can cost millions of dollars, while magnesium blocks cost a tiny fraction of that.
- Corrosion damage is catastrophic — structural failure of a ship's hull can lead to sinking, cargo loss, and danger to human life. Prevention is far cheaper than repair.
- Magnesium blocks are easy to replace — they can be bolted on and swapped during routine maintenance without dry-docking the entire ship.
- The alternative is worse — without sacrificial anodes, the iron hull itself corrodes, requiring expensive repairs, sandblasting, welding, and repainting.
Essentially: cheap, replaceable magnesium protects expensive, irreplaceable steel.
中文：
经济合理性：(1) 镁远比修复钢船体便宜——船体价值数百万，镁块成本极低；(2) 腐蚀损坏是灾难性的——结构失效可导致沉船、货物损失和人员危险；(3) 镁块易于更换——日常维护即可更换，无需大规模进坞；(4) 不用牺牲阳极的替代方案更昂贵。总之：用廉价可替换的镁保护昂贵不可替代的钢。
Further Q2¶
EN (Original): As opposed to the use of magnesium blocks, galvanized objects do not need their metal replaced. Do some research and determine why this is so.
中文翻译： 与镁块不同，镀锌物体不需要更换金属。研究原因。
Answer 答案:
EN:
Galvanized objects don't need zinc replacement because zinc forms a protective layer of zinc oxide (ZnO) and zinc carbonate (ZnCO₃) on its surface when exposed to air and moisture. Unlike iron rust (which is porous and flakes off), this zinc patina is:
- Dense and adherent — it bonds tightly to the surface
- Impermeable — it blocks further oxygen and water penetration
- Self-healing — if scratched, the exposed zinc quickly forms new protective oxide/carbonate
This means the zinc layer corrodes very slowly because the corrosion products themselves are protective (unlike iron rust). A hot-dip galvanized coating of ~85 μm can last 50+ years in rural environments.
In contrast, magnesium blocks on ships are continuously immersed in saltwater (a highly corrosive environment with no opportunity for a protective patina to form), so they corrode rapidly and must be replaced.
中文：
镀锌物体不需更换锌，因为锌在空气中形成氧化锌（ZnO）和碳酸锌（ZnCO₃）保护层。与铁锈不同，这层锌的腐蚀产物是：(1) 致密附着的；(2) 不透水的；(3) 自修复的——刮破后锌迅速形成新保护层。
因此锌层腐蚀极慢。而船体上的镁块持续浸泡在盐水中（强腐蚀环境，无法形成保护层），腐蚀快，需定期更换。
Further Q3¶
EN (Original): Explain why the salts put on winter roads to melt ice can hasten the corrosion of a car.
中文翻译： 解释为什么冬季道路撒盐融冰会加速汽车腐蚀。
Answer 答案:
EN:
Road salts (typically NaCl or CaCl₂) hasten car corrosion for several reasons:
-
Increased electrolyte conductivity — Salt dissolves in water to produce Na⁺ and Cl⁻ ions, creating an electrolyte solution. This dramatically increases the conductivity of the water film on the car's metal surface, allowing electrons to flow more easily in the corrosion galvanic cell, speeding up the electrochemical reactions.
-
Chloride ion attack — Cl⁻ ions are particularly aggressive. They can penetrate protective oxide films on metals, creating localized "pitting" corrosion that is especially destructive.
-
Lowered freezing point — Salt water remains liquid at lower temperatures, meaning the metal stays wet (in contact with liquid electrolyte) at temperatures where pure water would freeze, extending the period of active corrosion.
This is consistent with the experimental data: test tube 3 (NaCl, corrosion = 8) showed significantly more corrosion than test tube 1 (water alone, corrosion = 5).
中文：
道路盐加速腐蚀的原因：(1) 增加电解质导电性——盐溶于水产生离子，大幅增加水膜导电性，加速电化学反应；(2) 氯离子侵蚀——Cl⁻ 特别具有侵蚀性，能穿透金属保护性氧化膜，造成点蚀；(3) 降低冰点——盐水在更低温度下保持液态，延长金属接触液态电解质的时间。
与实验一致：试管3（NaCl，腐蚀 = 8）> 试管1（水，腐蚀 = 5）。
Further Q4¶
EN (Original): Some tools made of iron are not able to be plated. Based on your results, can you suggest a method of protecting these tools when they are being stored?
中文翻译： 有些铁制工具无法电镀。根据实验结果，你能建议一种储存时保护这些工具的方法吗？
Answer 答案:
EN:
Based on the experimental results, coating the tools with grease or oil is an effective protection method. Test tube 11 (grease-coated nail) had corrosion = 1, the lowest level along with the base and air-only controls.
Grease/oil provides barrier protection by forming a waterproof, airtight film that prevents water and oxygen from reaching the iron surface. This is:
- Easy to apply — no special equipment needed
- Easy to remove — wipe off with a cloth or solvent when the tool is needed
- Inexpensive — common machine oil or petroleum jelly works
- Reversible — doesn't permanently alter the tool
Additional recommendations based on the experiment:
- Store in a dry environment (tube 6: air only = 1, minimal corrosion)
- Avoid contact with salt, acid, or more noble metals (tubes 3, 4, 10 showed increased corrosion)
中文：
根据实验结果，建议涂抹油脂或机油保护工具。试管11（涂油脂）腐蚀 = 1，是最低水平。
油脂提供屏障保护，形成防水隔气膜，阻止水和氧气接触铁表面。优点：易涂抹、易去除、便宜、可逆。
其他建议：存放在干燥环境中（试管6：仅空气 = 1）；避免接触盐、酸或更贵重的金属。
术语表 | Terminology¶
| English 英文 | Chinese 中文 | Definition 定义 |
|---|---|---|
| Corrosion | 腐蚀 | Gradual oxidative degradation of metals |
| Rust | 铁锈 | Hydrated iron(III) oxide, Fe₂O₃·xH₂O |
| Tarnishing | 变色/失去光泽 | Thin oxidation layer on metal surface |
| Galvanization | 镀锌 | Coating iron with zinc for protection |
| Sacrificial Anode | 牺牲阳极 | More reactive metal that corrodes instead of protected metal |
| Cathodic Protection | 阴极保护 | Protecting metal by making it the cathode |
| Barrier Protection | 屏障保护 | Physical coating (grease, paint) blocking O₂ and H₂O |
| Oxidizing Agent | 氧化剂 | Species that causes oxidation (gets reduced itself) |
| Reducing Agent | 还原剂 | Species that causes reduction (gets oxidized itself) |
| Galvanic Cell | 原电池 | Spontaneous redox reaction produces electricity |
| Passivation | 钝化 | Formation of protective oxide layer (e.g., Al₂O₃ on aluminum) |
| Electrolyte | 电解质 | Substance that conducts electricity in solution |
| Pitting Corrosion | 点蚀 | Localized corrosion forming small cavities |
答案核对 | Answer Key Verification¶
ℹ️ 答案页未提供此项目答案。 This project has no answer key provided.
All answers are derived from the experimental data table and Standard Reduction Potentials from the data booklet (CH12_formula.pdf).