A method of depositing a conformal coating comprising: creating a vacuum within an interior volume of a steel tubular structure having an initial average roughness, Ra, of equal to or greater than 0.3 μm and less than 10 μm, wherein said tubular structure includes an internal surface and said interior volume; introducing an inert gas and optionally hydrogen to said interior volume and maintaining a pressure in the range of 1.3 Pa (10 mTorr) to 6.7 Pa (50 mTorr); sputter cleaning said internal surface by applying to said tubular structure a negatively biased, pulsed voltage ranging from 0.5 to 10 kV, with a pulse frequency in the range of 500 to 5,000 Hz at a pulse width of 1 to 100 microseconds for 30 to 120 minutes, while maintaining said pressure in the range of 1.3 Pa (10 mTorr) to 6.7 Pa (50 mTorr); following said sputter cleaning supplying a) precursor gas at a flow rate of 1 to 100 sccm and b) an inert gas at a flow rate of 1 to 200 sccm to said interior volume of said tubular structure, wherein said interior volume of said tubular structure is maintained at a total pressure ranging from 1.3 Pa (10 mTorr) to 13.3 Pa (100 mTorr) and said precursor gas is hexamethyldisiloxane; negatively biasing said tubular structure relative to ground with a pulsed voltage in the range of 0.5 to 10 kV at a pulse frequency of 500 to 5,000 Hz at a pulse width ranging from 1 to 100 microseconds; forming a plasma having a density and cyclically positioning said plasma density along the length of said tubular structure; generating positive ions of said plasma precursor gas which are deposited on said internal surface; and forming a coating having a thickness in the range of equal to or greater than 0.8 micrometers and up to 2 micrometers on said internal surface over a deposition period of 60 minutes to 120 minutes, wherein said coating exhibits a water contact angle of greater than 120° in mineral oil and said coating at a depth of up to 300 Angstroms comprises 50 to 60 atomic percent carbon, 20 to 30 atomic percent oxygen and 15 to 25 atomic percent silicon as measured by XPS. creating a vacuum within an interior volume of a steel tubular structure having an initial average roughness, Ra, of equal to or greater than 0.3 μm and less than 10 μm, wherein said tubular structure includes an internal surface and said interior volume; introducing an inert gas and optionally hydrogen to said interior volume and maintaining a pressure in the range of 1.3 Pa (10 mTorr) to 6.7 Pa (50 mTorr); sputter cleaning said internal surface by applying to said tubular structure a negatively biased, pulsed voltage ranging from 0.5 to 10 kV, with a pulse frequency in the range of 500 to 5,000 Hz at a pulse width of 1 to 100 microseconds for 30 to 120 minutes, while maintaining said pressure in the range of 1.3 Pa (10 mTorr) to 6.7 Pa (50 mTorr); following said sputter cleaning supplying a) precursor gas at a flow rate of 1 to 100 sccm and b) an inert gas at a flow rate of 1 to 200 sccm to said interior volume of said tubular structure, wherein said interior volume of said tubular structure is maintained at a total pressure ranging from 1.3 Pa (10 mTorr) to 13.3 Pa (100 mTorr) and said precursor gas is hexamethyldisiloxane; negatively biasing said tubular structure relative to ground with a pulsed voltage in the range of 0.5 to 10 kV at a pulse frequency of 500 to 5,000 Hz at a pulse width ranging from 1 to 100 microseconds; forming a plasma having a density and cyclically positioning said plasma density along the length of said tubular structure; generating positive ions of said plasma precursor gas which are deposited on said internal surface; and forming a coating having a thickness in the range of equal to or greater than 0.8 micrometers and up to 2 micrometers on said internal surface over a deposition period of 60 minutes to 120 minutes, wherein said coating exhibits a water contact angle of greater than 120° in mineral oil and said coating at a depth of up to 300 Angstroms comprises 50 to 60 atomic percent carbon, 20 to 30 atomic percent oxygen and 15 to 25 atomic percent silicon as measured by XPS.