3.
1. What does microbial corrosion mean?
2. What types of microbiological corrosion do you know?
3. What are the predominant types of bacteria associated with microbial corrosion?
4. Describe anaerobic corrosion.
17 . Summarize the general ideas developed in all the texts of the Unit 3.
Unit 4
ATMOSPHERIC CORROSION
1 . Read the international words, guess their meanings and give the Russian equivalents.
Temperature, atmospheric, industry, salt, characterize, system, chloride, aggressive, factor, material, sulphide, synergistic, parameter, conventional, function, manner, transferable.
2 . Read and translate the following verbs.
To classify, to attack, to expose, to increase, to promote, to contain, to contribute, to influence, to suffer, to comprise, to lead to, to correlate, to restrict, to find, to transfer, to know.
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.
Atmospheric corrosion accounts for more failures on both a tonnage basis and cost basis than any other type of environmental corrosion. Tremendous amounts of steel in automobiles, bridges ad buildings are exposed to the atmosphere and attacked by oxygen and water. The corrosion severity is increased when salt, sulfur compounds and other atmospheric contaminants are present. Atmospheric environments can be classified as: industrial, marine, rural, indoor.
Industrial environments contain sulfur compounds, nitrogen compounds, and other acidic agents that can promote the corrosion of metals. In addition, industrial environments contain a heavier loading of airborne particles, which also contribute to corrosion. Marine environments are characterized by the presence of chloride, an ion that is particularly detrimental to the corrosion behavior of many metals systems. Rural environments are the least corrosive of the atmospheric environments, being characterized by lower levels of acidic compounds and other aggressive species.
The principal factors influencing atmospheric corrosion for a given metal are moisture, temperature and the presence of contaminants in the environment. (From www.researchgate.net).
5 . Read the text again. Decide whether the following statements are true or false.
1. Urban environments are the least corrosive of the atmospheric environments.
2. The main factors influencing atmospheric corrosion for a given metal are pressure, velocity and temperature and the presence of contaminants in the environment.
3. Marine environments are characterized by the presence of copper and sulphur.
4. Atmospheric environments can be classified as: urban, marine and rural.
6 . Work in pairs. Translate the following sentences from English into Russian.
The term “atmospheric corrosion” comprises the attack on metal exposed to the air as opposed to metal immersed in a liquid. Atmospheric corrosion is the most prevalent type of corrosion for common metals.
Atmospheric corrosion is a subject of global concern because of its importance to the service life of equipment and durability of the structural materials. While there is a general agreement on the possible types of parameters that may lead to corrosion, these studies suffer severely from the lack of generality in the sense that their predictive capability is extremely poor. Conventional atmospheric parameters that may lead to metal corrosion comprise of weathering factors such as temperature, moisture, rainfall, solar radiation, wind velocity, etc. Air pollutants such as sulphur dioxide, hydrogen sulphide, oxides of nitrogen, chlorides have also been found to contribute to atmospheric corrosion. The complexity and diverse nature of the atmospheric pollutants make the prediction of the atmospheric corrosion difficult. The synergistic interaction of the variables must also be considered in the model for arriving at a definite solution. A direct approach to the problem is to measure the observed corrosion rates and the participating atmospheric parameters and correlate them. The correlation equations, thus derived, are known as damage functions and they have been found to be extremely useful, though in a restricted manner, as the results are not easily transferable from one place to another.
7 . Read the text. What is its main idea?
Особенностью атмосферной коррозии является возможность свободного подхода кислорода к корродирующей поверхности. Это обусловлено малой толщиной пленки и за счет конвекции перемешивания электролита. Именно поэтому даже в подкисленных электролитах атмосферная коррозия протекает с кислородной деполяризацией.
Также из-за тонкого слоя влаги на поверхности корродирующего металла анодный процесс идет с затруднением, а протекание катодного, наоборот, облегчается.
При работе гальванопар (galvanic couple) небольшая толщина пленки влаги тоже играет свою роль – увеличивается омическое сопротивление электролита.
Атмосферная коррозия сплавов, в основу которых входит железо (например, сталь), протекает с анодно-катодно-омическим контролем. Но в зависимости от некоторых условий (толщина, электропроводность пленки влаги, ее состав, природа металла) анодно-катодно-омический контроль может переходить в преимущественно анодный, преимущественно катодный или омический. (From www.okorrozii.com).
8 . Work in pairs. Interpret the following passage sentence by sentence.
The most common characteristic of metallic atmospheric corrosion is the localized character of its nucleation. Preferential nucleation sites depend on the metal structure and are associated to the presence of different phases or environmental pollutants on discrete areas of the metallic surface. In the case of carbon steel, nucleation starts with the formation of small protuberances of corrosion products at isolated points on the metallic surface,
