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Why is a cement coating used for internal corrosion protection on ductile iron pipes?

mild steel cement lined MSCL fittings malaysia
mild steel cement lined MSCL fittings malaysia
It was the city of where the first mild steel cement lined MSCL fittings malaysia with an internal cement mortar lining were installed.

The protection against internal and external corrosion of cast iron pipes, either by the action of water, or by the action of the soil with which it is in contact, as well as the quality of the water transported by the pipes, has been the subject of study, tests, and contribution of solutions to the various problems that have arisen over time.

Concerns that are now clear to us have been solved throughout the history of cast iron pipes. Externally and internally, the earliest grey cast iron pipes were provided unpainted. Because the pipe’s interior was found to be impacted by some types of water, a bituminous coating was proposed to protect the pipe’s interior. If the conveyed water was soft or acidic, however, it turned a reddish-brown colour, similar to that of acid, and a reduction in the section of the tube was discovered, resulting in a reduction in the flow rate that flowed through it.

  • The cause was in the effect called “tuberculation”, a process by which corrosive water penetrates the pores of the bituminous protection layer and develops rough mounds made up of products of iron corrosion that reduce the light of the tube and thus increase the resistance to the flow of the water.
  • It was necessary to find a type of coating capable of avoiding this process of tuberculation and thus improve the characteristics of the flow.

Cement mortar interior lining It was not until 1922 that the solution to the problem was found, which was no other than to internally coat the iron pipes with a layer of cement mortar. It was the city of where the first mild steel cement lined MSCL fittings malaysia with an internal cement mortar lining were installed.

mild steel cement lined MSCL fittings malaysia

However, although the tuberculosis issue could be solved, the problems did not end there.

The water supply managers observed that issues with soft water continued to appear and that the hardness and pH of the water increased during the first months after the line was commissioned. This is because cement mortars in contact with soft water tend to react with the calcium gratification of the mortars and form layers of calcium silicates in gel formation on the inner surface of the tube. In addition, this reaction favours the transfer of inorganic materials to the transported flow.

Conclusions

In short, what is intended from its historical origins with the use of interior cement lining is to provide the iron pipe, nowadays of ductile iron, with protection against the aggressiveness of the transported water, understood as a chemical alliance between cement, iron and water.

Depending on the characteristics of the fluid, the requirements of this protection vary, and therefore it  will be different.

Today, mild steel cement lined MSCL fittings Malaysia fine cements for specific applications that attend to different natures and problems. However, there are also mechanical protection coatings that could be the subject of a new article.

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