.

8. Work in pairs. Interpret the following passage sentence by sentence.

Much research has been done on the geometry of crevices and the influence on the propensity for the initiation of crevice corrosion. However, in practical terms, crevice corrosion usually occurs in openings a few tenths of a millimeter or less, and rarely is encountered where the crevice is greater than 2 mm.

Until the 1950s, crevice corrosion was thought to be due to differences in metal ion or oxygen concentration within the crevice and its surroundings. While these are factors in the initiation and propagation of crevice corrosion, they are not the primary cause.

Current theory supports the view that through a series of electrochemical reactions and the geometrically restricted access into the crevice migration of cations – chloride ions in particular – occurs. This alters the environment within, with a large reduction on pH and an increase in the cations by a factor as much as ten. The pH value can fall from a value of seven in the surrounding solution to as low as two within the crevice. As corrosion is initiated, it proceeds in an autocatalytic manner with all the damage and metal dissolution occurring within the crevice. Corrosion results in significant loss of metal under the surface of site of initiation. As a result, deep and severe cutting of the metal occurs.

9. Give English equivalents to the following word combinations and learn them by heart:

сопротивляться коррозионному воздействию среды

металлы и сплавы

коррозионное разрушение поверхности

объем разрушенного металла

расплавы электролитов

действие радиоактивного излучения

жизнедеятельность микроорганизмов

радиационная коррозия

10. Give Russian equivalents to the following word combinations and learn them by heart:

chloride ions

oxygen concentration

electrochemical reactions

wall thickness of a metal

wet corrosion

corrosion resistance

nonelectrolyte

ground corrosion

11. Translate the following sentences into Russian.

1. Uniform corrosion is considered the form of corrosion that can be tolerated in marine structures and equipment.

2. Crevice corrosion occurs at places with gaskets, bolts and lap joints where crevice exists.

3. Pitting corrosion can be prevented through proper selection of materials with known resistance to the service environment.

4. The reaction starts at the surface and proceeds uniformly.

5. The gap or crevice can be formed between two metals or a metal and non-metallic material.

6. The most severe attack occurs at the joint between the two dissimilar metals.

7. Copper produces a green film of corrosion product containing hydrated sulphate, or carbonate, or chloride.

8. Pipelines or tanks that are exposed to an electrolyte with a low oxygen concentration are generally anodic to the same material exposed to an electrolyte with a high oxygen content.

9. Localized corrosion can be defined as selective removal of metal by corrosion at small special areas or zones on a metal surface in contact with a liquid environment.

10. The process of corrosion requires four elements: an anode, a cathode, an electrolyte, and a metallic path.

12. Translate the following sentences into English.

1. Коррозия металлических сооружений наносит большой материальный и экономический ущерб.

2. Коррозия металлов бывает сплошной и местной.

3. Человечество несет огромные материальные потери в результате коррозии трубопроводов, деталей машин, судов, мостов, морских конструкций и технологического оборудования.

4. Наибольшую чувствительность к щелевой коррозии проявляют пассивные металлы в случае возможной их депассивации в щелях.