Speaking

Task 14. Find four possible continuations of the following statement. Make a brief paragraph on the basis of the resulting statements. You may use the following linking words and phrases: above all, chiefly, especially, primarily, principally, additionally/in addition, in other words, also, another thing is that..., apart from this,aside from that, as well as that, besides, for that matter, indeed, alternatively, except for, so far as, anyway, all told, and so forth, in brief, in conclusion.

The phenomenon of corrosion involves_________________

• reactions which lead to the creation of ionic species, by ether loss or gain of electrons;

• shaping of metal using localized compressive forces;

• degradation in quality of a usually metallic material due to chemical or electrochemical attack;

• removing metal through machining operations;

• process of formation of solid crystals precipitating from a solution;

• disintegration or decaying of an engineered material, mostly made of metals, into its constituent atoms due to chemical reactions with its surroundings;

• joining two or more pieces of metal together to form a single piece.

• electrochemical oxidation which causes a damage by producing oxides or salts of the original metal.

Writing

Task 15. Fill in the table below according to the information of the following text about corrosion processes.

Corrosion processes not only influence the chemical properties of a metal but also generate changes in its physical properties and its mechanical behavior. This is why the effects of corrosion are manifested in a variety of forms. The most common form is uniform corrosion, whereby there is a generalized, overall “attack” of the entire exposed surface of the metal, leading to a more or less uniform reduction in the thickness of the affected metal. In contrast, there is the process of localized corrosion, in which an intense attack takes place only in and around particular zones of the metal, leaving the rest of the metal unaffected; an example is pitting corrosion. Some other forms of corrosion are stress corrosion cracking, galvanic corrosion, selective alloy breakdown, intergranular corrosion, fatigue, friction, erosion, cavitation, hydrogen enbrittlement, biocorrosion, and high temperature oxidation.

It is easy to find everyday objects that show signs of corrosion. Traffic signs, streetlamp standards, metal barriers and fences, and many other items seen along roads are usually manufactured in galvanized steel (normal mild steel with a zinc coating). On such items it is common to see “white” corrosion (zinc oxide), characteristic of the oxidation of a zinc coating, often with spots of red rust also appearing that indicate that the steel base is being corroded.

The sea and the salty atmosphere are saline media that are highly aggressive to metals. Marine structures such as ships, bridges, and drilling rigs and platforms usually show signs of severe corrosion unless they have been properly protected. Cars kept near oceans show signs of corrosion.

Alloys of copper used in the casting of sculptures, and used externally on some buildings, usually show a greenish coloring that corresponds to a layer of corrosion product known as copper patina that gives some protection against further corrosion.

The degradation of reinforced concrete in buildings is commonly caused by the corrosion of the steel reinforcing bars within the concrete, rather than by the loss of the mechanical properties of concrete.

Effects of a generalized corrosion	Effects of a localized corrosion	Forms of corrosion	Examples of “white” corrosion	Examples of corrosion caused by saline media	Other examples of corrosion
1…………. 2………….	1…………. 2………….	1…………. 2………….	1…………. 2………….	1…………. 2………….	1…………. 2………….