METHOD OF APPLYING PROTECTIVE COATING ON INNER SURFACE OF MAIN PIPELINE Russian patent published in 2014 - IPC F16L58/02 C23D5/02 

FIELD: chemistry.

SUBSTANCE: in the method, preliminary cleaning of the inner surface of a pipe is carried out by degreasing with an alkaline solution, washing with deionised water and drying. Jet cleaning by a shotblasting method is then carried out using steel grit with size of not more than 1.6 mm to obtain surface finish Rz=30-120 mcm and salt content of not more than 50 mg/m=m². The inner surface then undergoes air blowing and preheating. A protective coating is then applied by airless spraying through a nozzle. The coating used is a solvent-free, polyamine-cured epoxide compound. The coating is cured by heating to temperature of 60-120°C and holding at said temperature for not less than 4 hours. Preheating is preferably carried out not later than 6 hours after preliminary cleaning and blowing with air to temperature higher than dew point by not less than 3°C, with relative air humidity of not more than 90%. Overall thickness of the "wet" film of the applied protective coating can be 300-800 mcm.

EFFECT: improved quality and durability of the coating.

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