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Corrosion Prevention

 

Frequently Faced Problems:

All types of materials viz. steel, cast iron, aluminum, stainless alloys, concrete etc. need to be protected from corrosion.Corrosion is the deterioration of the material, because of its reaction with the environment. This disintegration process can be due to chemical oxidation, atmospheric effects, galvanic couple reaction etc. Atmospheric corrosion accounts for more failures on both a tonnage and cost basis than any other type of environmental corrosion.

Tremendous amount of material in tanks, columns, ships, marine structures, pipelines…..are exposed to the atmosphere and attacked by “ oxygen and water”. High humidity is one of the main reason leading to corrosion of metal structures.

High humidity encourages blooming and flash rust when the surface is blasted visually clean and the coating is applied, which may result in premature coating failure. This problem can occur on any surface but is most common when there is a large continuous surface as in the interiors of storage tanks, process piping and reaction vessels.

While the surface is waiting for coating, small reduction in surface temperature or small increase in the humidity of the surrounding air can result in condensation, which causes immediate corrosion and negates the entire exercise.

General Recommendation:

Whatever the surface to be coated, from the preparation of the surface to the application of the first coat, the surface is subject to  environmental factors. The term “Hold the Blast” is commonly used and refers to the prevention of rust bloom from forming between the blasting and coating cycles.

As a result, general rules have been established which attempt to meet the specifications set by NACE and SSPC to maintain a 5°C differential between the air dew point and the surface to be coated in case of metals, and complete removal of dampness and moisture in the case of a non-metal like concrete, where even an apparently dry surface before coating can later show major blistering and de-lamination problems.

To avoid the above problem of corrosion, desiccant dehumidifier is used to remove moisture from the air at the surface so that the air dewpoint is lowered sufficiently for the metal.

Our Solution:

TDS provides dessicant based dehumidifiers along with other accessories and technical manpower to provide the desired humidity level.The desiccant based dehumidifier removes moisture from the air by chemical attraction rather than condensation. Dehumidification is used 24 hours per day until all the blasting and lining application is complete.

Dehumidifiers takes moist air  from  outside environment, and feed  dry air to the interiors where coating is to be carried out. The dry air prevents condensation and high relative humidity at the surface.

Benefits:
  • Coating life increases.
  • Fewer down times
  • Control over ambient conditions
  • Strict Control over project  completion schedule(24 hours working possible)
  • Coating and painting is possible as per paint manufacturers specification.
References:
  • IOCL
  • HPCL
  • BPCL
  • L & T

 

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