Lubricating coating composition suitable for lubrication of a threaded joint

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Quick Facts

Patent No.: US 6,869,111
App. No.: 10/201,932
Granted: Mar 22, 2005
Kind: B2

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Abstract

A lubricating coating composition in which at least one basic lubricant selected from a basic sulfonate, a basic salicylate, and a basic phenate is dissolved in a volatile solvent is applied to the frictional surface of a box and a pin constituting a threaded joint for oil well pipes. The composition may further contain one or more of a thermoplastic resin powder, another lubricant, and an extreme pressure agent. The surface roughness of the frictional surfaces preferably has an Rmax in the range of 5-40 micrometers.

Claims (32)

1. A threaded joint for metal pipes comprising a pin and a box capable of mating with each other, the pin having an externally threaded portion and an unthreaded metal contact portion, and the box having an internally threaded portion and an unthreaded metal contact portion, wherein at least one of the pin and the box has a lubricating coating formed on at least part of the threaded portion and/or unthreaded metal contact portion, the lubricating coating comprising at least 10 wt % of at least one basic lubricant selected from a basic sulfonate, a basic salicylate, and a basic phenate, wherein the at least one basic lubricant has a base number of at least 50 mg KOH/g, wherein the lubricating coating further comprises a thermoplastic resin.

2. A threaded joint according to claim 1 wherein the thermoplastic resin is in powder form.

3. A threaded joint according to claim 2 wherein the metal pipe is an oil well pipe.

4. A threaded joint according to claim 2 wherein the surface of the portion on which the lubricating coating is formed has a surface roughness, Rmax, in the range of 5-40 micrometers.

5. A threaded joint according to claim 1 wherein the metal pipe is an oil well pipe.

6. A threaded joint according to claim 1 wherein the lubricating coating further comprises at least one additive selected from a lubricant other than the basic lubricant and an extreme pressure agent.

7. A threaded joint according to claim 6 wherein the surface of the portion on which the lubricating coating is formed has a surface roughness, Rmax, in the range of 5-40 micrometers.

8. A threaded joint according to claim 6 wherein the metal pipe is an oil well pipe.

9. A threaded joint according to claim 1 wherein the surface of the portion on which the lubricating coating is formed has a surface roughness, Rmax, in the range of 5-40 micrometers.

10. A threaded joint for metal pipes comprising a pin and a box capable of mating with each other, the pin having an externally threaded portion and an unthreaded metal contact portion, and the box having an internally threaded portion and an unthreaded metal contact portion, wherein at least one of the pin and the box has a lubricating coating formed on at least part of the threaded portion and/or unthreaded metal contact portion, the lubricating coating comprising at least 10 wt % of at least one basic lubricant selected from a basic sulfonate, a basic salicylate, and a basic phenate, wherein the at least one basic lubricant has a base number of at least 50 mg KOH/g,