Corrosion
There are four main causes of corrosion:
- Aggressive acids
- Oxygen
- Galvanic action
- Biological organisms
Corrosive Acids, Corrosive or strong acids, such as sulphur dioxide, sulphuric, hydrochloric and nitric acid, found in most industrial areas. These acids are formed under certain industrial waste gases are washed out from the atmosphere soul water through the cooling tower. The presence of any of these acids will cause a drop in the circulating water pH. Water and carbon dioxide are found everywhere. When the carbon dioxide dissolved in water, it forms carbonic acid. This acid is less aggressive than acids already mentioned. Because it is always present, but no serious damage as a result of corrosive effect of this acid.
Corrosion with the help of Oxygen Corrosion oxygen another problem. Water that is sprayed into the air picks up oxygen. This oxygen is then held in the system. Oxygen reacts with any iron equipment. It forms an oxide of iron, which is a porous material. Showered and bubbles oxidized metal allows corrosion newly exposed metal.
Blistering also restricts water flow and reduces heat emission. Reaction rates between oxygen and iron rapidly increase as temperatures increase. Thus, the most severe corrosion occurs in places with a high temperature equipment with iron parts.
Oxygen is also affect the copper and zinc. Zinc is an outer coating of galvanized material. Here, the damage is much less difficult because the oxidation of zinc and copper forms an inert metal-oxide. It creates a protective film between the metal and the attacker oxygen.
Galvanic Effect of Galvanic corrosion is the third cause corrosion. Galvanic corrosion is mainly a reaction between two different metals in the electrical contacts. This reaction is electrical as well as chemical in nature. The following three conditions necessary for the production of galvanic effect.
- Two dissimilar metals having different electrochemical properties must be present.
- The electrolyte, solution through which the electric current can flow must be present.
- Electron way to connect these two metals.
Many different metals are used for the manufacture of air conditioning and refrigeration systems. Copper and iron are two dissimilar metals. Add solution containing ions, and the electrolyte is made. If two metals are placed in contact, not galvanic action will happen. Because it is two dissimilar metals such as iron and copper, come into contact with each other. This creates an electrical path or a path to the motion of the electron. This allows electrons to pass from copper and iron. As current leaves iron and opens her decision to return to copper, iron corrosion occurs. Copper and iron compounds common in systems of cooling.
Greater separation of metals in the galvanic series of results in their increased susceptibility to corrosion. For example, if platinum connected with magnesium, with the proper electrolyte, then platinum will be protected and magnesium corrosion. Because they are so far apart in terms of scale, corrosion will occur quickly. Cm. Table. 9-1. If iron and copper together, we can say, their relative positions in the series, iron corrosion, but to a lesser extent than magnesium referred to in the preceding example. However, corrosion would be sufficiently large to be really devastating. However, if the copper and silver were joined together, then the copper corrosion. Hence, the degree of corrosion is determined by the relative positions of the two metals in the galvanic series.
An improperly grounded electrical equipment or poor insulation can also initiate and expedite galvanic effect. Stray currents cause this type of corrosion is usually called the electrolytic corrosion. As a rule, it leads to formation of holes in the metal surfaces...
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Industrial