Corrosion cathodic protection against

Buried steel pipelines for the transport of gases (at pressures >4 bars) and of crude oil, brine and chemical products must be cathodically protected against corrosion according to technical regulations [1-4], The cathodic protection process is also used to improve the operational safety and economics of gas distribution networks and in long-distance steel pipelines for water and heat distribution. Special measures are necessary in the region of insulated connections in pipelines that transport electrolytically conducting media. 

Electroplating of magnesium for purposes of surface finishing, cathodic protection against corrosion, etc. 

CALCAREOUS COATING OR DEPOSIT - A layer consisting of a mixture of calcium carbonate and magnesium hydroxide deposited on surfaces being cathodically protected against corrosion, because of increased pH adjustment to the protected surface. 

The small cylindrical bars of magnesium attached to the steel ship provide cathodic protection against corrosion. 

Due to both carbonization and penetration of chloride ions, steel will pass from a passive to an active condition and (consequently) may corrode. If the mortar is completely surrounded by water, oxygen diffusion in wet mortar is extremely low so that the situation is corrosion resistant because the cathodic partial reaction according to Eq. (2-17) scarcely occurs. For this reason the mortar lining of waste pipes remains protective against corrosion even if it is completely carbonated or if it is penetrated by chloride ions. 

For economical and complete cathodic protection against external corrosion without harmful effects on nearby installations, the storage tank to be protected must have good coating and therefore require a low protection current density. In addition, it must have no electrical contacts with other buried installations, such as... 

Typical steel structures used underground in contact with soils are pipelines, utility pipings and pilings. Pipelines are generally protected against corrosion with coatings and by cathodic protection. Driven pilings are commonly used in bare condition. 

Buried steel pipeline can be protected against corrosion by cathodic protection. In this process, the steel pipe is connected to a more active metal, such as magnesium, that would corrode instead of the steel. Use the diagram to answer the following questions. 

An iron object is plated with a coating of cobalt to protect against corrosion. Does the cobalt protect iron by cathodic protection Explain. 

Another practical apphcation of electrolysis is electroplating—the coating of one metal, which is made the cathode in an electrolysis cell, with another metal, which is made the anode. For example, dull iron or steel surfaces are electroplated with chromium to provide a mirror-like finish and also to protect against corrosion. 

The electrode is set into a bipolar element, which consists of a channel frame surrounding the anodes, lined with titanium for protection against corrosion in the anolyte environment. The elements, with the anode side of one facing the cathode side of another, thereby forming a cell, are clamped together with tie-rods. The resulting assemblage has the appearance of a plate and frame filter-press—a commonly used piece of equipment for filtration operations. Hence, the term bipolar filter-press cell. ... 

A special type of coating for steel is used where exposure to crude oil and seawater is encountered, as in oil tankers. This involves an inorganic paint containing zinc powder which gives cathodic protection against localized corrosion. This has already been discussed in connection with the uses of lithium silicates in Chapter 2. Some further points are as follows. 

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