Lubricating coating composition suitable for tubular threaded joints

Abstract

A tubular threaded joint for connecting tubing or casing used to excavate oil wells have a lubricating coating formed from a lubricating coating composition comprising one or more basic lubricants selected from a basic sulfonate salt, a basic salicylate salt, a basic phenate salt, and a basic carboxylate salt and having biodegradability value (BOD) of at least 20% when measured after 28 days in seawater. The joint can be used without application of a compound grease containing heavy metals even in a country or region having severe environmental regulations.

1 . A lubricating coating composition comprising at least one basic lubricant selected from a basic sulfonate salt, a basic salicylate salt, a basic phenate salt, and a basic carboxylate salt, the composition having a biodegradability value (BOD) of at least 20% when measured after 28 days in seawater. 
   
   
       2 . A lubricating coating composition as set forth in  claim 1  which further comprises at least one additional lubricant selected from those having a higher biodegradability than that of the basic lubricant. 
   
   
       3 . A lubricating coating composition as set forth in  claim 2  wherein the additional lubricant is selected from a fatty acid metal salt and a wax. 
   
   
       4 . A lubricating coating composition as set forth in  claim 3  wherein the additional lubricant comprises at least one fatty acid metal salt and at least one wax. 
   
   
       5 . A lubricating coating composition as set forth in  claim 4  which contains 0-30 mass % of a volatile organic dissolving medium, the remainder comprising, when its total amount is taken as 100 parts by mass, 55-75 parts by mass of the basic lubricant, 20-25 parts by mass of the fatty acid metal salt, and 10-20 parts by mass of the wax. 
   
   
       6 . A lubricating coating composition as set forth in  claim 3  wherein the fatty acid metal salt is selected from alkaline earth metal salts of stearic acid or oleic acid. 
   
   
       7 . A tubular threaded joint constituted by a pin and a box each having a threaded portion and an unthreaded metal-to-metal contact portion as engaging portions, characterized in that the surfaces of the engaging portions of at least one of the pin and the box have a coating formed from a lubricating coating composition as set forth in  claim 1  and having a thickness of at least 10 micrometers. 
   
   
       8 . A tubular threaded joint as set forth in  claim 7  wherein the coating has a thickness of from 10 to 200 micrometers. 
   
   
       9 . A tubular threaded joint as set forth in  claim 7  wherein the surfaces have a surface roughness of 5-40 micrometers Rmax. 
   
   
       10 . A tubular threaded joint as set forth in  claim 9  wherein the surface roughness is formed by treating the surfaces by a method selected from sand or grit blasting, acid etching, phosphating, electroplating with iron or copper, and blast plating with zinc or a zinc alloy, 
   
   
       11 . A lubricating coating composition as set forth in  claim 4  wherein the fatty acid metal salt is selected from alkaline earth metal salts of stearic acid or oleic acid. 
   
   
       12 . A lubricating coating composition as set forth in  claim 5  wherein the fatty acid metal salt is selected from alkaline earth metal salts of stearic acid or oleic acid. 
   
   
       13 . A tubular threaded joint constituted by a pin and a box each having a threaded portion and an unthreaded metal-to-metal contact portion as engaging portions, characterized in that the surfaces of the engaging portions of at least one of the pin and the box have a coating formed from a lubricating coating composition as set forth in  claim 2  and having a thickness of at least 10 micrometers. 
   
   
       14 . A tubular threaded joint constituted by a pin and a box each having a threaded portion and an unthreaded metal-to-metal contact portion as engaging portions, characterized in that the surfaces of the engaging portions of at least one of the pin and the box have a coating formed from a lubricating coating composition as set forth in  claim 3  and having a thickness of at least 10 micrometers. 
   
   
       15 . A tubular threaded joint constituted by a pin and a box each having a threaded portion and an unthreaded metal-to-metal contact portion as engaging portions, characterized in that the surfaces of the engaging portions of at least one of the pin and the box have a coating formed from a lubricating coating composition as set forth in  claim 4  and having a thickness of at least 10 micrometers. 
   
   
       16 . A tubular threaded joint constituted by a pin and a box each having a threaded portion and an unthreaded metal-to-metal contact portion as engaging portions, characterized in that the surfaces of the engaging portions of at least one of the pin and the box have a coating formed from a lubricating coating composition as set forth in  claim 5  and having a thickness of at least 10 micrometers. 
   
   
       17 . A tubular threaded joint as set forth in  claim 8  wherein the surfaces have a surface roughness of 5-40 micrometers Rmax.