Threaded pipe with surface treatment
A threaded metallic pipe for oil extraction industry has a threaded end portion with treated surface in which the metal surface has a roughness (Ra) comprised of 2.0 μm and 6.0 μm, which is covered by a uniform layer ( 7 ) of a dry corrosion inhibiting coating and a second uniform layer ( 8 ) of dry lubricant coating. Alternatively the layers ( 8, 9 ) combined into one uniform layer ( 9 ) of a dry corrosion inhibiting coating containing a dispersion of particles of solid lubricant.
1. A pipe segment ( 1 ) of definite length for oil extraction industry made of a metal, having a central portion with a substantially cylindrical wall and at least a threaded end portion ( 3 , 4 ) covered with a surface protection characterised in that the metal surface in the threaded end portion ( 3 , 4 ) has a surface roughness (Ra) comprised between 2.0 μm and 6.0 μm, said surface protection being constituted by a first uniform layer ( 7 ) of a dry corrosion inhibiting coating made of an epoxy resin containing particles of Zn and a second uniform layer ( 8 ) of dry lubricant coating covering said first layer ( 7 ).
2. The pipe segment according to claim 1 , wherein the first layer ( 7 ) has a thickness comprised between 10 and 20 μm.
3. The pipe segment according to claim 1 , wherein the second layer ( 8 ) is made of an inorganic binder and a mixture of particles of solid lubricants, one of which is molybdenum disulphide.
4. The pipe segment according to claim 3 , wherein the second layer ( 8 ) has a thickness between 10 and 20 μm.
5. The pipe segment according to claim 1 , wherein said threaded end portion is of conical or frusto-conical envelope.
6. The pipe segment according to claim 1 , wherein said threaded end portion is of cylindrical envelope.
7. The pipe segment according to claim 5 , wherein the pipe is threaded as a male member of a connection.
8. The pipe segment according to claim 5 , wherein the pipe is threaded as a female member of a connection.
9. A pipe segment ( 1 , 2 ) of definite length for the oil or gas extraction industry made of a metal, with a central portion with a substantially cylindrical wall and a threaded end portion ( 3 , 4 ) covered with a surface protection, characterised in that the metal surface of the threaded end portion ( 3 , 4 ) has a surface roughness (Ra) comprised between 2.0 μm and 6.0 μm, and said surface protection is constituted by one uniform layer ( 9 ) made of a dry corrosion inhibiting coating containing a dispersion of particles of solid lubricant.
10. The pipe segment according to claim 9 , wherein the uniform layer ( 9 ) contains a dispersion of particles of molybdenum disulphide.
11. A threaded pipe joint for oil or gas extraction industry made of male and female threaded pipe members with male and female threads respectively, wherein at least one of the pipe members has a pipe segment according to claim 1 .
12. A process to make a threaded end portion of a metallic pipe for oil extraction industry with the characteristics according to claim 1 , comprising the steps of:
a) Providing surface roughness (Ra) of the pipe metal at least near the threaded portion with value comprised between 2.0 μm and 6.0 μm;
b) Providing a first uniform layer ( 7 ) of a dry corrosion inhibiting coating over the metal surface at least near the threaded portion;
c) Providing a second uniform layer ( 8 ) of dry lubricant coating over the first uniform layer ( 7 ) of corrosion inhibiting coating at least near the threaded portion.
13. The process to make a threaded end portion of a metallic pipe for oil or gas extraction industry with the characteristics according to claim 1 , comprising the steps of:
a) Providing surface roughness (Ra) of the pipe metal at least near the threaded portion with value comprised between 2.0 μm and 6.0 μm;
b) Providing a first uniform layer ( 9 ) of a dry corrosion inhibiting coating containing a dispersion of particles of solid lubricant over the pipe metal surface at least near the threaded portion.
14. The process according to claim 12 , wherein the surface roughness (Ra) of the metal is achieved by abrasive blasting.
15. The process according to claim 12 , wherein the surface roughness (Ra) of the metal is achieved by depositing a phosphate layer on the metal surface.