Тандем - 2, шлакоблочные станки, бетоносмесители

Производство оборудования и технологии


The components present in fluids which promote the corrosion of casing in drilling and producing operations are oxygen, carbon dioxide, hydrogen sulfide, salts and organic acids. Destruction of met als is influenced by various physical and chemical factors which localize and increase corrosion damage.

The conditions which promote corrosion include:

• Energy differences in the form of stress gradients or chemical reactivities across the metal surface in contact with a corrosive solution.

• Differences in concentration of salts or other corrodants in electrolytic so-

• Differences in the amount of solid or liquid deposits on the metal surface, which are insoluble in the electrolytic solutions.

• Temperature gradients over the surface of the metal in contact with a cor­rosive solution.

• Compositional differences in the metal surface.

Corrosion of metals continues provided electrically conductive metal and solu­tion circuits are available to bring corrodants to the anodic and cathodic sites. Four conditions must be present to complete the electrochemical reactions and corrosion circuit:

1. Presence of a driving force or electrical potential. The difference in reaction potentials at two sites on the metal surface must be sufficient to drive electrons through the metal, surface films and liquid components of the corrosion circuit.

2. Presence of an electrolyte. Corrosion occurs only when the circuit between anodic and cathodic sites is completed by an electrolyte present in water.

3. Presence of both anodic and cathodic sites. Anodic and cathodic areas must be present to support the simultaneous oxidation and reduction reactions at the metal-liquid interface. Metal at the anode ionizes.

4. Presence of an external conductor. A complete electron electrolytic cir­cuit between anodes and cathodes of the metal through the metal surface films, surrounding environment and fluid-solid interfaces is necessary for the continuance of corrosion.

In the environment surrounding the metal, the presence of water provides con­ducting paths for both corrodants and corrosion products. The corrodant may be a dissolved gas, liquid or solid. The corrosion products may be ions in solution, which are removed from the metal surface, ions precipitated as various salts on metal surfaces and hydrogen gas.

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