Carbon steel pipe can be supplied uncoated (bare), with a temporary external coating to minimize rusting in transit and storage, or special anti-corrosion coated as specified.
A temporary external coating are including Black lacquer paint, varnish lacquer coated, oil coated by a coating machine.
Where the steel pipes are required to be supplied hot-dip zinc coated, they shall first be thoroughly descaled, washed as necessary and then dipped in a bath of molten zinc, containing not less than 98.5 % by mass of zinc, at a temperature suitable to produce a complete and uniformly adherent coating of zinc .The Galvanized pipe are coated with zinc inside and outside by the hot-dip process. The weight of the zinc coating can be 150-500g per square meter.
When the steel pipes are applied for fire protection or sprinkler, the pipe surface should be red epoxy coated.
On-ground and under-ground line pipes and fluid transmission pipes are required a special anti-corrosion coated, like 3PE, FBE and 3PP. During the anti-corrosion, the external surfaces of the pipe shall be free of any injurious levels of contaminants such as oil, grease, and salts prior to the application of the coating. Prior to blast cleaning, the pipe shall be preheated to remove moisture by preheating with a controlled temperature. Blast clean level and coating thickness should as per standard requirements. The cutback length for both ends of the pipe shall be 50-20mm or as specified.
Mainly standard of anti-corrosion:
|3PEThree layer of Polyethylene||DIN 30670|
|FBEFusion bond epoxyLiquid or power||AWWA C210 |
|3PP Three layer of Polypropylene||DIN 30678|
|HDGHot dipped galvanized||BS1385 |
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Tianjin United Steel Pipe Co., Ltd