Metal Corrosion. Electroplating (Защита от металлов от коррозии. Гальванотехника). Я. Ившин
main idea?
Почва является вместилищем необычайно обильной и разнообразной микрофлоры, представленной многочисленными группами бактерий, плесневыми грибками, дрожжевыми организмами и т. п.
Количество разнообразных бактерий, приходящееся на 1 грамм почвы, достигает сотен миллионов, а иногда и десятков миллиардов. Основная масса микроорганизмов встречается в верхних горизонтах почвы, однако и в подпочвенных слоях они содержатся в значительном количестве. В некоторых случаях эти организмы могут вызывать интенсивную коррозию, получившую наименование микробиологической коррозии.
Действие микроорганизмов сводится или к непосредственному влиянию на скорость анодной и катодной реакций, или к созданию коррозийной среды.
Наибольшее значение и распространение в почвенных условиях имеет анаэробная коррозия.
Коррозионный процесс в анаэробных условиях заключается в том, что благодаря жизнедеятельности микроорганизмов в среде, окружающей подземное сооружение, сульфаты восстанавливаются и преобразуются в сероводород. Последний взаимодействует с железом, образуя сернистое железо. Освободившийся при восстановлении сульфатов кислород обеспечивает деполяризацию катода, на котором должен накапливаться водород в связи с растворением железа. Таким образом, через катодную деполяризацию бактериальный процесс стимулирует развитие коррозии.
(From www.groont.com).
8 . Work in pairs. Interpret the following passage sentence by sentence.
Corrosion resulting from the attachment and activities of microorganisms on metal surfaces is referred to as microbiologically influenced corrosion (MIC) or biocorrosion. It occurs in diverse environments and is not limited to aqueous submerged conditions, but also takes place in humid atmospheres. It is an electrochemical process in which the participation of microorganisms is able to initiate, facilitate, or accelerate the corrosion reactions without changing the process’s electrochemical nature. MIC is a result of interactions that are often synergistic between the metal surface, abiotic corrosion products, and microbial cells and their metabolites. The latter includes organic and inorganic acids and volatile compounds, such as ammonia and hydrogen sulfide. Microbiologically mediated reactions do not result in a unique type of corrosion, but they can induce localized corrosion, change the rate of corrosion and also inhibit corrosion.
Most MIC studies have focused on bacterial involvement; however, under aerobic conditions, other single-celled organisms, such as fungi, yeast and diatoms, can influence corrosion. The predominant types of bacteria associated with MIC are sulfate-reducing bacteria (SRB), sulfur-oxidizing bacteria, iron-oxidizing/reducing bacteria, manganese oxidizing bacteria, and bacteria secreting organic acids and slime. These organisms coexist within a biofilm matrix on metal surfaces, functioning as a consortium in a complex and coordinated manner. The various mechanisms of biocorrosion reflect the variety of physiological activities carried out by these different types of microorganisms when they coexist in biofilms. Despite decades of study on MIC, it is still not known with certainty how many species of microorganisms contribute to corrosion, and researchers continue to report on the formation of biofilms by an ever-widening range of microbial species.
9 . Give English equivalents to the following word combinations and learn them by heart:
деятельность микроорганизмов
различные среды
электрохимический процесс
органическая кислота
металлическая поверхность
сероокисляющие бактерии
образование биопленок
микробные виды
аэробные условия
синтетическая коррозия
10 . Give Russian equivalents to the following word combinations and learn them by heart:
inhibit corrosion
entire surface
organic acid
hydrogen sulfide
manganese oxidizing bacteria
predominant type
biofilm matrix
physiological activities
11 . Translate the following sentences into Russian.
1. Some bacteria can directly reduce metal atoms to ions.
2. Hydrogen ions are produced, along with hydroxyl ions, by the breakdown of water, and the electrons to form atomic hydrogen from the hydrogen ion are produced by the oxidation of atomic iron.
3. The source of electrons is the oxidation of the metal while the electron sink is reduction of hydrogen ions.
4. MIC has been observed as one of the major causes of underground pipeline corrosion.
5. Sulphate reducing bacteria (SRB) have been reported to be responsible for extensive corrosion in hydrocarbon industry.
6. There are other types of corrosion-enhancing bacteria such as iron-reducing bacteria, iron-oxidizing bacteria, nitrifying bacteria, methanogenic bacteria and so on.
7. New technologies that may assist mitigation are basically based on using certain biological technologies (such as use of “good” bacteria against corrosion-related bacteria).
8. Almost all known engineering materials (from carbon steel to stainless and duplex stainless steels and also non-ferrous metals such as copper alloys and non-metals such as some polymers and concrete) are susceptible to MIC.
9. Gas velocity and temperature in the pipeline play a significant role in determining if and where corrosion damage may occur.
10. Accelerated Low Water Corrosion (ALWC) is a particularly aggressive form of MIC that affects steel piles in seawater near the low water tide mark.
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