Question

Железо. Коррозия металлов (помогите ответить,нужно для экзамена...всё по этим темам)

Answer 1

Железо подвержено коррозии, так как оно относительно активный металл, а образующиеся оксиды не защищают её от дальнейшего окисления. 
В процессе естественного окисления железа воздухом образуется так называемая ржавчина, состоит она, в основном, из Fe2O3, Fe(OH)2, Fe3O4, FeO. 
Поэтому в промышленности добавляют к железу присадки (никеля или хрома) тем самым получая так называемую "нержавейку". Либо покрывают железо защитными плёнками металлов, широко известны - жесть (лужёная сталь), оцинковка (сталь покрытая цинком), меднение и латунирование тоже роже распространено в значительной мере. 

Answer 2

Corrosion of Metals

Corrosion is a natural process that occurs when metals react with their environment, resulting in the deterioration of the metal. It is a common issue that affects various types of metals, including iron, steel, aluminum, and copper. Corrosion can have significant economic and safety implications, as it can weaken structures, reduce the lifespan of equipment, and cause failures in critical systems.

Factors Affecting Corrosion: Several factors contribute to the corrosion of metals. These include:

1. Presence of Moisture: Moisture is a critical factor in the corrosion process. It provides the necessary medium for the electrochemical reactions that lead to corrosion. Water, humidity, and moisture in the air can all contribute to the corrosion of metals.

2. Oxygen: Oxygen is another essential component for corrosion to occur. It reacts with the metal surface, forming metal oxides or hydroxides, which are often the visible signs of corrosion.

3. Electrolytes: Electrolytes, such as salts and acids, can accelerate the corrosion process. They increase the conductivity of the metal's environment, allowing for faster electrochemical reactions.

4. Temperature: Higher temperatures generally increase the rate of corrosion. Elevated temperatures can accelerate the chemical reactions involved in corrosion, leading to more rapid metal degradation.

5. Presence of Impurities: Impurities in metals can promote corrosion by creating localized areas of different electrochemical potentials. These areas, known as galvanic cells, can result in accelerated corrosion at the interface between the impurity and the metal.

Types of Corrosion: Corrosion can manifest in various forms, depending on the specific conditions and the type of metal involved. Some common types of corrosion include:

1. Uniform Corrosion: This type of corrosion occurs evenly across the entire surface of the metal. It often results in a gradual loss of material and a general thinning of the metal.

2. Galvanic Corrosion: Galvanic corrosion occurs when two different metals are in contact with each other in the presence of an electrolyte. The more active metal (anode) corrodes faster, while the less active metal (cathode) remains relatively unaffected.

3. Pitting Corrosion: Pitting corrosion is characterized by the formation of small pits or cavities on the metal surface. It can be highly localized and may penetrate deep into the metal, leading to structural weaknesses.

4. Crevice Corrosion: Crevice corrosion occurs in confined spaces or crevices where stagnant solutions can accumulate. The lack of oxygen and the buildup of corrosive substances in these areas can accelerate the corrosion process.

5. Stress Corrosion Cracking: Stress corrosion cracking is a type of corrosion that occurs under the combined influence of tensile stress and a corrosive environment. It can lead to the formation of cracks and fractures in the metal.

Prevention and Control: Preventing or controlling corrosion is essential to maintain the integrity and longevity of metal structures and equipment. Some common methods for corrosion prevention include:

1. Protective Coatings: Applying protective coatings, such as paint, enamel, or specialized corrosion-resistant coatings, can create a barrier between the metal surface and the corrosive environment.

2. Galvanic Protection: Using sacrificial anodes or cathodic protection systems can help protect metals from galvanic corrosion. These systems involve connecting a more active metal to the metal being protected, diverting the corrosion reactions to the sacrificial metal.

3. Corrosion Inhibitors: Corrosion inhibitors are chemicals that can be added to the environment surrounding the metal to slow down or prevent corrosion. They work by forming a protective layer on the metal surface, inhibiting the electrochemical reactions.

4. Proper Design and Material Selection: Designing structures and equipment with corrosion-resistant materials and considering factors such as drainage, ventilation, and insulation can help minimize the risk of corrosion.

5. Regular Maintenance and Inspection: Regular inspection and maintenance of metal structures and equipment can help identify and address corrosion issues before they become severe. This includes cleaning, repairing coatings, and removing any accumulated corrosion products.

It is important to note that while these measures can significantly reduce the risk of corrosion, complete prevention is often challenging. Therefore, ongoing monitoring and maintenance are crucial to manage and mitigate the effects of corrosion.

I hope this information helps you in your exam preparation! Let me know if you have any further questions.