Я. Ившин - Metal Corrosion. Electroplating (Защита от металлов от коррозии. Гальванотехника)

6. При относительной влажности, близкой к 100 %, или при непосредственном увлажнении металла (дождь, туман) на поверхности происходит образование видимых фазовых слоев воды.

7. Рост оксидной пленки происходит в первые секунды и минуты.

8. Предельная толщина пленок на железе 30-40 А, на нержавеющих сталях – 10-20 А.

9. Анодный процесс осложняется тем, что продукты коррозии экранируют поверхность металла.

10. Загрязнение атмосферы газами, пылью резко ускоряет коррозию. Это явление наблюдают в промышленных центрах, особенно в присутствии в воздухе SO 2, NH 3, H 2S,C1 2, HCl.

13 . Translate the following word combinations.

Anodic process – продукты коррозии – industrial cluster – оксидная пленка – oxygen depolarization – продукты горения – wind velocity – корродирующий металл – sulphur oxide – функции ущерба – corrosive surface – экранировать поверхность металла – chemical nature – оксидная пленка – nucleation site – предельная толщина – atmospheric pollutant – загрязнение газами – carbon oxides – коррозионные язвы – relative humidity.

14 . Give the definitions of the words and word combinations.

1. Radiation is …

2. Condensation is …

3. Humidity is …

4. Pressure is …

5. Convection is …

1 5 . Give the example(s) of the atmospheric corrosion.

16 . Answer the following questions using texts from Unit 4.

1. What is the definition of atmospheric corrosion?

2. What may cause atmospheric corrosion?

3. Name the principal factors of atmospheric corrosion.

4. What do industrial environments contain?

17 . Summarize the general ideas developed in all the texts of the Unit 4.

1 . Read the international words, guess their meanings and give the Russian equivalents.

Accelerate, electrical, contact, conductive, galvanic, phenomenon, attack, uniform, nature, service, condition, film, erosion, limit, effective, action, anode, cathode, test, region.

2 . Read and translate the following verbs.

To depend on, to remove, to insulate, to reverse, to separate, to utilize, to try, to perform, to allow, to expect, to indicate, to generate, to apply, to diminish, to connect, to match.

3 . Match the English phrases from column A with the Russian phrases in column B.

4. Read and translate the text. Summarize it in Russian.

Accelerated corrosion which can occur when dissimilar metals are in electrical contact in the presence of an electrolyte (i.e. conductive solution). An example of this corrosion phenomenon is increased rate of corrosion of steel in seawater when in contact with copper alloys. Galvanic attack can be uniform in nature or localized at the junction between the alloys depending on service conditions. Galvanic corrosion can be particularly severe under conditions where protective corrosion films do not form or where they are removed by conditions of erosion corrosion.

Prevention or Remedial Action: selection of alloys which are similar in electrochemical behavior and/or alloy content; area ratio of more actively corroding material (anode) should be large relative to the more inert material(cathode); use coatings to limit cathode area; insulate dissimilar metals; use of effective inhibitor.

(From www.galvanic-corrosion.com) .

5 . Read the text again. Decide whether the following statements are true or false.

1. Accelerated corrosion phenomenon is decreased rate of corrosion of steel in seawater when in contact with copper alloys.

2. Galvanic corrosion which can occur when dissimilar metals are in chemical contact in the presence of an electrolyte.

3. Galvanic corrosion can be mainly partial under conditions where protective corrosion films form or where they are removed by conditions of erosion corrosion.

6 . Work in pairs. Translate the following sentences from English into Russian.

Many people utilized the standard galvanic series of materials in seawater to predict service performance relative to galvanic corrosion. In fact, this galvanic series is specific to only seawater at near ambient conditions. Other factors such as temperature and the presence of other chemical species can greatly affect the rank ordering of materials.

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